Distribution and species composition of mass occurrences of large-sized sponges in the northeast Atlantic

Progress in Oceanography Progress in Oceanography 61 (2004) 57–98 www.elsevier.com/locate/pocean

Distribution and species composition of mass occurrences of large-sized sponges in the northeast Atlantic A.B. Klitgaard a

a,*

, O.S. Tendal

a

Zoological Museum, University of Copenhagen, Universitetsparken 15, DK-2100 København Ø, Denmark Received 13 March 2004; revised 14 April 2004; accepted 17 June 2004 Available online 21 August 2004

Abstract The geographic and bathymetric distribution of ‘‘ostur’’, that is mass occurrences of large-sized astrophorid demosponges, first recognized at the Faroe Islands during the internordic BIOFAR programme (Marine Benthic Fauna of the Faroe Islands), are mapped for the northeast Atlantic. This is done on the basis of information obtained during the sampling of the BIOICE programme (Benthic Invertebrates in Icelandic Waters) as well as during cruises at Karmoy (southwest Norway), the Trondheim Fjord (middle Norway), the Koster area (southwest Sweden) and the Denmark Strait (southeast Greenland). In addition, information has been acquired from Nordic and German biologists and fishermen regarding the occurrence of ‘‘ostur’’. These data together with the sparse information in the literature show that the geographic distribution of the ‘‘ostur’’ areas follows two band-shaped arcs, defined by the Norwegian Atlantic Current and the Irminger Current. The local occurrence of ‘‘ostur’’ is, however, to a great extent dependent on areas of variable topography where a hard bottom is present. The results show that two main types of ‘‘ostur’’ can be recognized in the northeast Atlantic. Firstly a boreal ‘‘ostur’’ which is dominated by Geodia barretti, Geodia macandrewi, Geodia atlantica, Isops phlegraei, Stryphnus ponderosus and Stelletta normani, and occurs around the Faroe Islands, Norway, Sweden, parts of the western Barents Sea and south of Iceland. Secondly a cold water ‘‘ostur’’ characterized by the same genera but represented by different species, viz. Geodia mesotriaena, Isops phlegraei pyriformis and Stelletta rhaphidiophora, which is found north of Iceland, in most of the Denmark Strait, off East Greenland and north of Spitzbergen. A number of hexactinellid species are also represented in the cold water ‘‘ostur’’, the most frequently occurring being Schaudinnia rosea. Suggestions are given regarding the possible causes for observed changes in the distribution of ‘‘ostur’’ as well as to the biological importance of these areas.
2004 Elsevier Ltd. All rights reserved. Keywords: Mass occurrences; Sponges; Astrophorida; Porifera; Distribution; Species compostion; North Atlantic

*

Correspondence to: A.B. Klitgaard, Danish Polar Center, Strandgade 100 H, DK-1401 København K, Denmark. Fax: +45 32 88 01 01. E-mail addresses: [email protected] (A.B. Klitgaard), [email protected] (O.S. Tendal). 0079-6611/$ - see front matter
2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.pocean.2004.06.002

58

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

1. Introduction During the internordic BIOFAR programme 1987–1990 (Marine Benthic Fauna of the Faroe Islands (NE Atlantic); Nørrevang, Brattegard, Josefson, Sneli, & Tendal, 1994) accumulations of large-sized demosponges (Fig. 1) were recorded in certain areas of the outer shelf around the Faroes. It turned out that the local fishermen had known about this phenomenon for years and often mark such areas as ‘‘ostur’’, meaning ‘‘cheese bottom’’, on their charts and in their log books. Traditionally when trawling, they avoid ‘‘ostur’’ because of the risk of catching several tons of sponges, overfilling the gear and damaging the catch. Fiskirannso´knarstovan (The Faroese Fishery Laboratory) included some areas with ‘‘ostur’’ in a book of charts showing the distribution of areas where the bottom is unsuitable for trawling in Faroese waters (‘‘To´v’’, Anonymous, 1988). Apart from this, the phenomenon had gone unnoticed in earlier investigations, nor had even the most characteristic sponge species previously been recorded from the Faroese area (Brøndsted, 1932). We made a special effort during the BIOFAR programme to map in detail the geographic distribution and the bathymetric range of the ‘‘ostur’’ areas around the Faroe Islands, which entailed either one or both of us taking part in all nine cruises and compiling a variety of relevant information (Klitgaard, Tendal, & Westerberg, 1997). In areas with ‘‘ostur’’, up to 50 species of sponges can occur, and of these about 20 can reach sizes exceeding 5 cm in maximum diameter. Clearly dominant in terms of biomass, size and quantity per catch, are four species of the family Geodiidae (Geodia barretti Bowerbank, 1858; Geodia macandrewi Bowerbank, 1858; Geodia atlantica (Stephens, 1915) and I. phlegraei Sollas, 1880) and the stellettid Stryphnus ponderosus (Bowerbank, 1866) (Astrophorida, Demospongiae); single specimens are sometimes more than 70 cm in diameter and 24 kg wet weight. A rough definition of an area with ‘‘ostur’’ is ‘‘a restricted area where large-sized sponges are strikingly common’’ (Klitgaard et al., 1997). Around the Faroe Islands sponges can constitute more than 90% of the biomass of the catch other than the benthic fishes. Information from Danish, Faroese, German, Icelandic and Norwegian fishermen and biologists, and our own results and experience from many cruises show that ‘‘ostur’’ areas with accumulations of large-sized astrophorid (tetractinellid) sponges are not solely a Faroese phenomenon but exist throughout the eastern Atlantic boreal region. Literature information supports this but mostly in general terms only, either confirming that the species occur in the given area, or stating that large quantities of sponges have been found (e.g., Alander, 1942; Koltun, 1966, 1970; Rezvoj, 1928; Zenkevitch, 1963). Other than the BIOFAR investigations around the Faroe Islands, detailed investigations of sponge-dominated areas as a biological phenomenon, have only

Fig. 1. A trawl sample from an area with ostur west of The Faroes at 480 m depth (BIOFAR St. 540; Nørrevang et al., 1994). A.B. Klitgaard photo.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

59

been undertaken off Bear Island, West of Spitzbergen, and in some parts of the western Barents Sea (Blacker, 1957, 1965; Dyer, Cranmer, Fry, & Fry, 1984; Erekovsky, 1995; Filatova, 1938). The aim of the present investigation is to map the geographic and bathymetric distribution of ‘‘ostur’’ areas from East Greenland to northern Norway and to Spitzbergen on the basis of the information taken from all available sources. Geographic differences with respect to presence and dominance of the characteristic species are presented and possible causes for changes in the distribution as well as the biological role of such areas are discussed.

2. Materials and methods The results compiled here originate from several different sources and so are accurate to varying degrees. Using as measures the taxonomic composition (ideally: number and size of specimens, and the species) and the location (ideally: position, depth, bottom type, bottom temperature, gear and volume of catch), the information level ranges from the notion that ‘‘. . . there are large amounts of sponges in that area. . .’’ to fully sorted, counted, and identified catches from established positions. The most important factor in this investigation has been that we personally took part, either alone or together, in numerous cruises off East Greenland, around Iceland and the Faroes, and off the coasts of Sweden and Norway. We have seen fresh samples from nearly all over the region and have been able to analyse fully at least some catches on deck. Thus, compared to the actual bulk of the catches only a small amount of material was brought back. Cruise reports, fishery catch sheets, log books, questionnaires and nautical maps are generally precise concerning the location, although it must be kept in mind that ‘‘bottom type’’ is often more descriptive of the roughness of the bottom than of the sediment composition; when stones are mentioned one has to remember that smaller fractions may have been present but not recorded. The taxonomic information from these sources is sparse, but it has sometimes been possible to verify identifications through personal interviews. It is a strange fact that the literature searches have yielded comparatively little information, only a few fully worked trawl catches being previously reported. There are some cases where large amounts of sponges are mentioned, but no position is given. On the other hand, when station number or position is given the species list has to be compiled from the records of each individual species listed in the taxonomic survey of the paper in question. Additional information on sampling procedure and station data has often had to be sought in publications other than those treating the sponges, and is sometimes not referred to anywhere. 2.1. Field work Sampling where the authors took part is listed for each geographic area in Table 1 and commented on below. All sponges sampled were initially fixed in 4% borax-buffered formaldehyde. After at least 2–3 weeks, they were rinsed in freshwater and transferred to 80% ethanol. The maximum dimensions of all the geodiid sponges were measured either in the field or in the laboratory. Most of the material is currently stored at the Zoological Museum, University of Copenhagen except for the BIOICE sponges that are at the Icelandic Institute of Natural History, Reykjavik. 2.1.1. The Faroe Islands During the BIOFAR programme, we sampled a transect south of Suderø Bank, southeast of the Faroe Islands, in April 1990 during a one-day cruise with the Faroese coast guard vessel Tjaldrid. At each of six different localities, three hauls with triangular dredge (80 · 80 · 80 cm) were taken across an area indicated

Locality

The Faroe Islands Transect south of Suderø Bank

Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td

90040101-1 90040101-2 90040101-3 90040102-1 90040102-2 90040102-3 90040103-1 90040103-2 90040103-3 90040104-1 90040104-2 90040104-3 90040105-1 90040105-2 90040105-3 90040106-1 90040106-2 90040106-3

HM 237 HM 242

Norway, the Trondheim Fjord, 1989, 1994 Seaward Fjord Stjørnfjorden T 94052604 T 94052609 T 94052608 T 94052605 Trondheimsleia T 94052611 Off Brettingneset T 94060902 Off Breidvikta˚a T 94052603 T 94052601 Kalurdalsbukta T 94052702 Off Kinebbneset T 94052509 T 94052510 Off Berganneset T 94052504 Off Esvikneset T 94052706

Position

Depth (m)

Temperature (C)

Gear

N

E/W

6106.96 0 6106.95 0 6107.01 0 6107.07 0 6106.92 0 6106.88 0 6107.09 0 6106.94 0 6106.89 0 6107.38 0 6107.24 0 6107.36 0 6107.56 0 6107.27 0 6107.56 0 6106.99 0 6107.09 0 6107.11 0

0620.26 0 W 0620 0 W 0619.91 0 W 0610.26 0 W 0610.57 0 W 0610.12 0 W 0600.05 0 W 0600.72 0 W 0600.12 0 W 0551.30 0 W 0551.49 0 W 0551.08 0 W 0546.17 0 W 0546.46 0 W 0546.45 0 W 0535.62 0 W 0535.17 0 W 0534.50 0 W

214–217 215–219 217–218 252–248 253–248 255–247 275–280 272–277 278–276 282–283 282–281 280–283 275–276 275–277 276–269 289–289 285–289 286–292

Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td

5907 0 5916 0

0510 0 E 0456 0 E

160 157

BT BT

6343.80 0 6344.00 0 6344.24 0 6343.80 0 6340.60 0 6339.25 0 6337.50 0 6337.49 0 6335.92 0 6332.48 0 – 6330.68 0 6332.36 0

0957.75 0 E 0956.80 0 E 0957.43 0 E 0957.75 0 E 0947.27 0 E 0948.25 0 E 0945.07 0 E 0945.10 0 E 0945.85 0 E 0950.47 0 E – 0950.92 0 E 0954.22 0 E

200–30 200–50 175–30 150–30 130–30 400–100 200–50 150–40 300–120 100–45 – 160–100 500–100

Td Td Td Td Td Td Td Td Td Td Td Td Td

Comments

c. 1.0 m3 sponges c. 1.5 m3 sponges

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

SW-Norway The Karmoy area

Expedition and St.no.

60

Table 1 Station list for the authors own sampling, arranged according to geographical areas. Explanations are to be found at the bottom of the table

Off Røberg

Ma˚neskinnsviken Off Geitaneset Off Vorpneset Loddeberget

Off Omborneset Rørvikgrunnen at Hindrem Munkholmen Middle Fjord Nordviksundet

Off Balvika

Inner Fjord Skarnsundet, western slope Skarnsundet, eastern slope

Beitstadfjorden, Fjordgrunnen Beitstadfjorden, Korsholmflua

Beitstadfjorden, off Galgneset Sweden, the Koster area South of Krugglo¨

94060604 89050904 89050903 94060603 94060606 89051805 89051804 89051802 94060602 94060301 94060302 94060303 94060304 94060306 89051207 89051205 89033001 94060201

6329.03 0 6328.00 0 – 6329.10 0 6327.13 0 6327.00 0 6326.90 0 – 6330.87 0 6333.10 0 6333.18 0 6333.00 0 6333.12 0 6334.00 0 6334.20 0 6335.50 0 6327.90 0 6328.00 0

0959.27 0 E 1000.00 0 E – 0959.41 0 E 0957.76 0 E 0957.80 0 E 0958.80 0 E – 1009.58 0 E 1016.00 0 E 1016.00 0 E 1019.00 0 E 1018.94 0 E 1025.60 0 E 1026.30 0 E 1031.20 0 E 1023.60 0 E 1024.40 0 E

250–60 150–50 150–75 100–35 500–90 350–50 350–75 200–50 150–50 200–50 100–30 280–90 150–30 150–40 70–30 100–50 300–100 150–40

Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td Td

T T T T T

94061401 94053003 94053004 94053005 94053006

6345.40 0 6344.74 0 – 6349.33 0 6349.38 0

1059.18 0 E 1059.60 0 E – 1103.17 0 E 1103.22 0 E

300–70 250–25 200–25 225–50 150–40

Td Td Td Td Td

T T T T T T T T T T T T

94053109 89051105 94053107 94053108 89051106 94053105 94053106 94053103 89051103 89051101 89051102 94053101

6351.40 0 6352.45 0 6351.50 0 6351.50 0 6351.50 0 6352.12 0 6352.08 0 6354.50 0 6354.70 0 – – 6354.90 0

1103.90 0 E 1103.10 0 E 1104.15 0 E 1104.10 0 E 1104.40 0 E 1104.25 0 E 1104.20 0 E 1104.80 0 E 1107.10 0 E – – 1057.87 0 E

175–40 180–60 200–90 150–20 150–40 150–50 130–30 130–40 100–30 80–30 70–50 150–50

Td Td Td Td Td Td Td Td Td Td Td Td

V 07.05.1975 V 16.02.1975

5853.1 0 –

1105.5 0 E –

150–60 200–50

Rd Rd

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Aksnestangen

T T T T T T T T T T T T T T T T T T

c. 50 l of sponges c. 30 l of sponges (continued on next page) 61

62

Table 1 (continued) Locality

Bjo¨rns Rev East of Ramso¨ Ulvillarna

North Iceland

The Denmark Strait

Greenland The Denmark Strait

Position

Depth (m)

Temperature (C)

Gear

Comments

Rd Rd Rd Rd Rd Rd

c. c. c. c. c. c.

50 30 20 30 50 50

c. c. c. c. c. c. c. c.

350 350 250 100 100 100 120 150

N

E/W

5852 0 – 5849.8 0 5849.2 0 – –

1106 0 E – 1105.5 0 E 1104.8 0 E – –

200–120 210–120 130–85 200–130 225–150 225–150

BIOICE 2292 I 78

6227.91 0 6037 0

2240.22 0 W 2752 0 W

1204 1505

3.9 4.5

BIOICE 2022 BIOICE 2769

6636.69 0 6835.18 0

1243.32 0 W 1656.23 0 W

325 519


0.40

BIOICE BIOICE BIOICE BIOICE BIOICE BIOICE BIOICE I 90

2499 2501 2516 2518 2923 2926 2928

6618.32 0 6625.24 0 6636.85 0 6636.94 0 6543.63 0 6550.79 0 6539.28 0 6445 0

2630.66 0 W 2550.32 0 W 2522.69 0 W 2533.59 0 W 2907.99 0 W 2846.45 0 W 2739.95 0 W 2906 0 W

629 630 680 749 704 540 678 1070


0.50
0.40
0.50
0.50 1.14 0.33 5.79 4.4

Ds Ds Ds Ds Ds Td Td

94PA0090001 94PA0090002 94PA0090009 94PA0090010 94PA0090019 94PA0090020 94PA0090043 94PA0090062 I 92

6724.7 0 6737.4 0 6713.6 0 6719.10 6543.1 0 6602.0 0 6654.3 0 6709.1 0 6444 0

2638.1 0 W 2750.3 0 W 3032.9 0 W 3029.1 0 W 3423.7 0 W 3246.4 0 W 2744.8 0 W 3032.3 0 W 3252 0 W

306–291 274–257 441–410 241–226 360–274 282–328 372–381 467–448 1838

0.33 0.78 0.93

BT BT BT BT BT BT BT BT

V V V V V V

11.07.1975 17.06.1976 24.05.1975 07.05.1975 18.10.1976 21.03.1977

2.38 2.07 0.17 0.63 1.4

l l l l l l

of of of of of of

sponges sponges sponges sponges sponges sponges

AT

Td Td

l l l l l l l l

sponges sponges sponges sponges sponges sponges sponges sponges

Stations in the Trondheim Fjord are listed from the entrance of the seaward basin towards the inner basin. Position data of all hauls (18) in the transect south of Suderø Bank at the Faroe Islands are shown. For trawl stations (the Karmoy area, and the Denmark Strait) only samples where more than 100 litres of astrophorid sponges were collected are included. All stations from which geodiid or stellettid specimens were collected are shown for the Trondheim Fjord, while only samples containing several specimens are included for the Koster area and Iceland. Td = Tjaldrid; HM = R/V Ha˚kon Mosby, V = Virgo, I = Ingolf. Td = Triangular dredge, Bt = Bottom trawl, Rd = Rectangular dredge, At = Agassiz trawl, Ds = Detritus sledge.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Iceland South Iceland

Expedition and St.no.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

63

as ‘‘ostur’’ in ‘‘To´v’’ (Anonymous, 1988). The identity of the dominant sponge species and their relative quantities in the catch were recorded for each haul but no material was kept. 2.1.2. Norway In April 1993, ABK participated in a cruise with R/V Ha˚kon Mosby west of Karmoy, southwest Norway. Samples were taken in an area known for the occurrence of ‘‘ostur’’ with a Campel 1800 bottom trawl with a mesh size of 40 mm (cod end) and a measured wingspread of 17.5–18.5 m. All sponges were sorted as soon as the catch came on deck. The number of specimens of each geodiid species and of S. ponderosus were recorded at each station together with the maximum dimension of each specimen, but only a few specimens were preserved. A representative selection of other sponge species was kept from all samples. After being informed by the director of the Trondheim Biological Station that astrophorid sponges are common in some places in the Trondheim Fjord, central Norway, ABK conducted preliminary sampling in March and May 1989 at a number of localities. More extensive sampling was accomplished in all three basins of the Trondheim Fjord in May–June 1994 (Table 1). All sampling was done from R/V Harry Borthern using a triangular dredge (70 · 70 · 70 cm). As standard procedure, the sponges from each haul were immediately sorted and the abundance of species of the family Geodiidae and of S. ponderosus and the maximum dimension of each specimen were recorded, but only a selection of the specimens was preserved, together with a representative selection of other sponge species present. 2.1.3. The Swedish west coast Working from the Tja¨rno¨ Marinbiological Laboratory, sponges were collected by OST at several localities in the Koster Sound during the years 1974, 1975, 1976 and 1977. Sampling was conducted from the small research vessel Virgo using a rectangular dredge (80 · 20 cm). A representative collection was kept, with some notes of numbers, size and form. 2.1.4. Iceland During 11 BIOICE cruises in 1991–1996, with the Icelandic research vessel Bjarni Sæmundsson, the Norwegian R/V Ha˚kon Mosby and the Faroese R/V Magnus Heinason, more than 600 samples were taken using either a detritus sledge (opening 80 · 20 cm), a Rothlisberg & Pearcy epibenthic sledge (opening 100 · 33 cm), a triangular dredge (80 · 80 · 80 cm) or an Agassiz trawl (opening 200 · 80 cm). Either one or both of us participated in nine of these cruises and sponge material was obtained from the other two cruises. The stations were distributed all around Iceland, at depths ranging from about 50 to 2400 m. At each station the number of specimens as well as the maximum dimension of each specimen of geodiid and in some cases ancorinid species were registered on board. A representative selection of all sponge species was kept from each of the stations. 2.1.5. Greenland, The Denmark Strait During a cruise with the Greenlandic R/V Paamiut in September–October 1994 sponges were collected by ABK in the Denmark Strait (Table 1). All sampling was done using a SKJERVOY 3000 bottom trawl with a mesh size of 20 mm (cod end) and a wingspread of ca. 19 m. At two stations (GF 94PA0090001 and GF 94PA0090002) the number of I. p. pyriformis (Vosmaer, 1882) and at one station (GF 94PA0090002) the number of Geodia mesotriaena (Hentschel, 1929) were very large; in these cases the maximum dimension of all specimens was measured on board and only a selection of the specimens preserved. At the remaining stations, all specimens of these two species were kept. The number of specimens and the maximum dimension of each specimen of the other geodiid and ancorinid species were registered on board at all stations but only some of the specimens were preserved. A representative selection of other sponge species was kept from all hauls.

64

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

2.2. Other information Data on other areas where ‘‘ostur’’ occurs have been compiled through making enquiries to a number of Danish, Faroese, German, Icelandic and Norwegian biologists and trawler captains (Table 2). These data are shown for separate geographical localities. 2.2.1. Norway Sponge accumulations are reported on the eastern slope of the Norwegian Trench west of Karmoy, southwest Norway, and along the northwest coast of Norway. 2.2.2. The Barents Sea Sponge accumulations are known to occur in the Barents Sea and data on two such localities were obtained from a Faroese trawler officer. 2.2.3. Iceland Information on mass occurrences of large-sized sponges on the northern part of the Reykjanes Ridge southwest of Iceland have been supplied by Icelandic fishery biologists. 2.2.4. The Denmark Strait The Greenland Institute for Natural Resources regularly surveys shrimp stocks in the Denmark Strait. Several cruise leaders have supplied not only information as to where large accumulations of sponges occur, but also samples of the commonest sponge species from their trawl samples (Table 2). Information about large catches of sponges was obtained during R/V Walther Hervig cruise no. 51, ‘‘Overflow-expedition’’, in 1973 in the Denmark Strait (Table 2). Distribution maps were prepared using the Geographic Information System MapInfo for Windows and the American Digital CartographyÕs (ADC) WorldMap for MapInfo digital atlas (Figs. 2, 3 and 5). Dr. Ha˚kan Westerberg kindly supplied us with topographical information used in preparing Fig. 3. Dr. Birger Larsen kindly permitted the use of his topographical chart of the Denmark Strait (Fig. 6).

3. General descriptions of topography The bottom topography strongly affects the circulation and the distribution of water masses, which in turn influences the presence and abundance of benthic organisms, such as sponges. Below, a short description is given of the topography of each area investigated taking the Faroe Islands as starting point and moving eastwards and westwards, respectively, following the two main arcs of the North Atlantic Current; the Norwegian Atlantic Current and the Irminger Current. 3.1. Topography 3.1.1. The Faroe islands The Faroe islands are situated on the Greenland–Scotland Ridge, which forms the oceanographic threshold between the North Atlantic Ocean and the Norwegian-Greenland Sea. In the Faroese area, the ridge system is divided into two parts, the Iceland-Faroe Ridge to the north and the Wyville Thomson Ridge to the south. Both have sill depths of about 500 m. They are separated by the Faroe-Shetland Channel which continues into the Faroe Bank Channel between the Faroese plateau and the Faroe Bank. The Faroe Bank Channel has a sill depth about 850 m and so is the deepest channel through the Greenland– Scotland Ridge (Hansen, 1985; Hansen & Østerhus, 2000).

Table 2 Data on ‘‘ostur’’ contributed by Danish, Faroese, German, Icelandic and Norwegian biologists and fishermen. Explanations are to be found at the bottom of the table Source of record

Expedition and St. no./Locality

SW-NORWAY, the Norwegian Trench and the Karmoy area Stein Tveite

Position

Depth (m)

Temperature (C)

Comments

E/W 0605 0 E 0547 0 E 0412 0 E 0436 0 E 0433 0 E 0438 0 E 0432 0 E 0455 0 E 0553 0 E 0447 0 E 0435 0 E 0458 0 E 0500 0 E 0603 0 E 0558 0 E 0456 0 E

375 335 285 280 275 265 265 255 250 250 240 232 220 160 150 145

‘‘Sponge haul’’ – – – – – – – – – – – – – – –

Svend Lemvig Stein Tveite

HM 1991, 45

Svend Lemvig

HM 1991, 27

5815 0 5819 0 5850 0 5819 0 5915 0 5912 0 5931 0 5835 0 5817 0 5916 0 5854 0 5855 0 5838 0 5818 0 5820 0 5916 0

Tromsøflaket Trollbukta

7028 0 6850 0

1720 0 E 1320 0 E

220–290 220–280

‘‘ostur’’ –

NW of Presteneset

7150 0 7130 0

3920 0 E 2100 0 E

330–350 320–430

‘‘ostur’’ –

Reykjanes Ridge – – – – – – –

6252.40 0 6230.20 0 6210.60 0 6208.20 0 6127.90 0 6134.90 0 6127.30 0 6103.80 0

2228.00 0 W 2436.00 0 W 2525.50 0 W 2639.20 0 W 2739.00 0 W 2736.40 0 W 2641.50 0 W 2725.06 0 W

967–972 1213–1344 925–928 946–929 954–1003 1064–1210 1237–1145 1152–1294

Sponges ca. 800 kg sponges 5000–10,000 kg sponges ca. 500 kg sponges ca. 1000 kg sponges ca. 2000 kg sponges >20,000 kg, trawl full of sponges 15,000-20,000 kg sponges

6737.5 0 6733.7 0

2626.8 0 W 2752.5 0 W

323 292–289

NW-NORWAY Jon Simonsen

THE BARENTS SEA Jon Simonsen

SW-ICELAND Sigmar A. Steingrimsson

GREENLAND, the Denmark Strait Per Kanneworff 92PA0160001 Klaus Lehmann 90MA0200057

0.56 0.87

65

ca. 100 kg sponges ca. 150 l sponges (continued on next page)

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

N

66

Expedition and St. no./Locality

Position N

E/W

Per Kanneworff

92PA0160002 89SI0240055 92PA0160046 WH 637/73 89SI0240080 89SI0250075 WH 642/73 92PA0160052 SM 1987, 104 WH 651/73 WH 652/73 WH 653/73 WH 654/73 SM 1987, 67

6732.8 0 6706.1 0 6714.0 0 6622 0 6622.5 0 6609.1 0 6525.2 0 6607.5 0 6533 0 6516.5 0 6513 0 6511 0 6503 0 6506 0

2638.1 0 W 2746.3 0 W 3022.2 0 W 2746 0 W 2703.8 0 W 2809.4 0 W 2939.5 0 W 3236.7 0 W 3153 0 W 3328 0 W 3326 0 W 3321 0 W 3304 0 W 3656 0 W

Chr. Karrer Per Kanneworff Chr. Karrer Per Kanneworff ? Chr. Karrer

?

Depth (m)

Temperature (C)

Comments

300 383–388 254–197 340–320 513—519 469–470 968–981 274–313 688–727 505–460 785–767 980–955 1503–1535 228–216

0.70 0.70 2.57 0.5 1.4 1.7 0.5 1.73 – 7.4 3.3 3.0 1.4 2.74

ca. 200 kg sponges Many sponges c. 2000 kg sponges 10–15 baskets of sponges Many sponges Many sponges 3–4 baskets of sponges ca. 300 kg sponges ca. 1500 kg sponges ca. 20 baskets of sponges ca. 20 baskets of sponges 30 baskets of sponges >50 baskets of sponges ca. 2000 kg sponges

HM = R/V Ha˚kon Mosby, SM = R/V Shinkai Maru, WH = R/V Walther Herwig. The gear was a bottom trawl in all cases. The data for SW-Norway are arranged according to depth. The data for the Denmark Strait are arranged as stations northeast and southwest of the Kangerdlugssuaq Channel respectively (compare with Fig. 6).

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Table 2 (continued) Source of record

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

67

Only sparse information has previously been published on the surficial sediments of the Faroese area (Spa¨rck, 1929). Data from the BIOFAR sampling shows that these sediments differ between the western and eastern sides of the Faroes. On the western side of the plateau, as well as on top of the Faroe and Bill Bailey Banks, the sediments mostly consist of shell gravel and sand. Whereas on the eastern side of the plateau, in the shelf break areas (both west and east), on the slopes of the banks, and on the Iceland-Faroe Ridge as well as on the Wyville Thomson Ridge the sediments are mostly sand and gravel mixed with cobbles, stones and scattered boulders (Klitgaard, 1992; map compiled from a number of sources, unpublished; Bruntse & Tendal, 2001; Klitgaard et al., 1997; Nørrevang et al., 1994). 3.1.2. The Karmoy area The Norwegian Trench extends from off the Norwegian coast at about 62N, southwards around the coast and into the Skagerak as a deep channel 300–350 m deep. The sediment is generally mud, but there are areas of stones and gravel where the bathymetry is slightly shallower than the surrounding areas and where more dynamic current conditions keep smaller particles from settling (Norwegian Fishery Chart, 559). 3.1.3. The Trondheim Fjord The Trondheim Fjord is situated on the west coast of Norway; its seaward sill is at 6340 0 N, 0945 0 E and its inner end at 6445 0 N, 1130 0 E. The Fjord has three basins. The Agdenes sill at the entrance which has a sill depth of 195 m is approximately 135 km from the innermost end of Beitstadfjorden (Jacobson, 1983). The seaward basin has a surface area of 746 km2 and a volume of 158 km3 with mean and maximum depths of 212 and 600 m, respectively. The sill separating the seaward basin and the middle basin is at Tautra and has a depth of ca. 60 m. The middle basin has a surface area of 441 km2, a volume of 57 km3 and a mean and maximum depth of 130 and 440 m, respectively. The connection between the middle basin and the innermost basin, Beitstadfjorden, is through Skarnsundet which is 700 m wide with a sill depth of 130 m. Beitstadfjorden has a surface area of 233 km2, a volume of 20 km3 and a mean and a maximum depth of 86 and 270 m, respectively. The northern and western slopes of the Trondheim Fjord are steeper than the southern and eastern slopes, being about 7 in Beitstadfjorden and increasing to about 25 at Agdenes (Jacobson, 1983; Wendelbo, 1970). Large amounts of mud are carried to the Fjord by six large rivers, but only a little sediment is present on the steeper rocky slopes. On the Agdenes sill and the Tautra sill there are areas with sand (Wendelbo, 1970). The general experience from sampling in the Fjord is that when dredging on the steeper parts of the slopes, the samples often contained no sediment either because none is present or what little there was has been washed out during recovery. On the gentler slopes sediments consist mostly of mixtures of mud, gravel, stones, and shellgravel derived from Modiolus modiolus (L., 1758), Arctica islandica (L., 1767) and sometimes Acesta excavata (Fabricius, 1779) and Chlamys sp., but also gravel or blocks of the stone coral Lophelia pertusa (L., 1758). 3.1.4. Koster sound The Skagerak can be considered as part of a Fjord bounded by the southeastern coast of Norway, the southwestern coast of Sweden and the northwestern coast of Denmark; the Koster area is situated at the bottom of the outer Fjord, while the rest is in the Kattegat and parts of the Baltic. Topographically, the sound between the northern section of the Swedish Skagerak coast and the Koster Islands is the inner end of the Skagerak channel that is up to 700 m deep. Off the entrance to the Oslofjord the bottom of the channel shoals to a depth of 150–200 m and broadens out. North of the Koster Islands it again narrows and rapidly deepens to about 500 m. It then turns south and, after passing a threshold area of 100–110 m depth, runs between the Koster Islands and the mainland as a narrow channel more than 20 km long, and 200–250 m deep, ending in shallow water near the Va¨der Islands. The sediment on the bottom of the Koster Sound is

68

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

mud. The steep sides are irregular in relief and sediment-free rocky areas with interspersed pockets of mud are found down to about 220 m (Hansson, 1976; Swedish Charts, 93, 935). 3.1.5. Iceland Together with the Faroe Islands, Iceland is a large plateau situated on the Greenland-Scotland Ridge which is roughly delineated by the 600 m depth contour, and rather steep gradients down to depths of about 1000 m. Where it is best developed, the shelf is more than 100 km wide. All around Iceland it is incised by many narrow submarine canyons 200–300 m deep which are most numerous off the northeast and southeast coasts. To the west, the shelf is bounded by the 620 m deep Denmark Strait Channel. To the east the shelf falls steeply off to about 400 m and extends as the 150-km wide crest of the Iceland-Faroe Ridge, which has a maximum depth of 490 m. Due north from the Icelandic coast extends a 200-km long ridge, which reaches the surface at the small island of Kolbeinsey. Between the coast and Kolbeinsey the bottom topography is complicated and includes a series of seamounts. From the southwest corner of Iceland, the Reykjanes Ridge extends 1500 km to the southwest and gradually deepens to about 2000 m depth (Fleischer, Holzkamm, Vollbrecht, & Voppel, 1974; Schott, 1912; Nautical Charts from the Icelandic Hydrographic Service, 31, 41, 51, 61, 71 & 81). The surface sediments around Iceland are very variable and sometimes very mixed. Toward the deep channel of the Denmark Strait, the sediments are predominantly sand with more or less silt and mud, and scattered stones. Along the north coast there are wide areas of volcanic silt, but there are also hard bottoms, especially in the Kolbeinsey Ridge area, and locally muddy spicule mats from astrophorid sponges are found. Over most of the surface of the Iceland-Faroe Ridge the bottom is gravelly, with occassional boulders, silt and mud is to be found locally in small troughs. Off the south coast of Iceland, there are extensive submarine plains covered with well sorted material of volcanic origin, with gravel close to the coast, and grading to silt and mud in deeper waters. Here and there, small escarpments and ridges provide hard substrate. The Reykjanes Ridge area has a highly varied topography with extensive areas of hard substrates interspersed with large patches of soft bottom (Spa¨rck, 1929; station information from BIOICE cruises 1991–1996). 3.1.6. The Denmark Strait The shelves of East Greenland and Iceland almost merge in the Denmark Strait, as the Greenland-Iceland Ridge, which is the western extension of the Greenland-Scotland Ridge (Larsen, 1983; Nilsen, 1983). The topography of the Denmark Strait has been well described by Larsen (1983, p. 426): ‘‘The East Greenland shelf in the Denmark Strait is approximately 100 km wide at 68N, north of the ridge, and approximately 150 km wide off Angmagssalik, south of the ridge, but broadens to 250 km on the ridge off Kangerdlugssuaq Fjord. The shelf is well-defined north and south of the ridge, but on the ridge between 66N and 67N no major break appears in the bathymetric profile. The water depths on the Greenland shelf are chiefly 200–400 m. In contrast to this, the depth of the Iceland shelf in the Denmark Strait is only 0–200 m and there is a marked shelf break. The insular shelf of Iceland is thus clearly distinguishable from the Greenland part of the ridge. The Greenland-Iceland Ridge is traversed by the 20–30 km wide Denmark Strait Channel’’. The channelÕs maximum depth is 620 m. The East Greenland coast is deeply incised by deep fjords and glacier-filled valleys, and these extend across the shelf as deep submarine troughs. The outer shelf is characterized by broad trough-like channels extending almost across the shelf and by prominent banks (Larsen, 1983; Nilsen, 1983). Knowledge of the surface sediments in the Denmark Strait is sparse. Clay deposits are found in the fjords and fjord extensions and in a few local depressions in the transverse channels, but are rare on the Greenland shelf between 65 and 68N. The surface of the shelf is extensively scoured by icebergs at depths down to 350 m and locally as deep as 650 m. Similarly, most of the surface of the banks and parts of the

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

69

channel floors are completely covered by scour-marks, and the upper 5–10 m of the material on the seafloor is more or less disturbed and mixed (Larsen, 1983). All sampling on R/V Paamiut in 1994 was done using a bottom trawl (mesh size 20 mm) and all sediment was washed out during recovery so none was retained in any of the samples. However, at some stations several litres of muddy spicule mats were collected, and some of the specimens of G. macandrewi sampled had thick ‘‘furs’’ of spicules filled with mud on their lower sides and some of the specimens of G. barretti had stones of various sizes and gravel incorporated underneath. This together with the varying abundance and composition of sponge species in the samples indicates that different sediment categories are patchily distributed.

4. Results A detailed description of the geographic and bathymetric distributions of ‘‘ostur’’ in the North Atlantic is given below and summarized in map form (Fig. 2). As ‘‘ostur’’ first were recognized at the Faroe Islands, this area is taken as starting point followed by the remaining areas in the same order as in Section 3. A short description of the general hydrography is included for each area. 4.1. Distribution of ‘‘ostur’’ (Fig. 2) 4.1.1. The Faroe Islands A large area on the southeastern plateau south of Suderø Bank is marked as ‘‘ostur’’ in ‘‘To´v’’ (Anonymous, 1988). A transect sampled by the authors in April 1990 had its first station situated at the western limit of the area; the next two stations were within the area, and the remaining three were along the southern edge of the areaÕs eastern part (Fig. 3 and Table 3). St. Td 90040101 was outside the ‘‘ostur’’ area, only few sponges were taken and included no geodiids or ancorinids. The next two stations were clearly within the ‘‘ostur’’ area, as large quantities of sponges were sampled, especially of S. ponderosus; also represented by several specimens were G. barretti, G. macandrewi and I. phlegraei. While each haul was dominated by astrophorid species, comparison of the six hauls of St.nos Td 90040102 and Td 90040103 showed that the relative proportions of the geodiid species and S. ponderosus varied between hauls, indicating that within the ‘‘ostur’’ area these species varied in abundance. The last three stations were also dominated by sponges but only one specimen of I. phlegraei, S. ponderosus and Stelletta normani Sollas, 1880 was collected at St. Td 90040104; only one G. barretti and a few specimens of S. normani at St. Td 90040105; and neither geodiids nor ancorinids were taken at St. Td 90040106. At these three stations the dominant sponges were Phakellia ventilabrum (Johnston, 1842), Phakellia robusta Bowerbank, 1866; Petrosia crassa (Carter, 1876) and Mycale lingua (Bowerbank, 1866) at St. Td 90040104; P. ventilabrum, P. robusta and M. lingua at St. Td 90040105; and Thenea levis Lendenfeld, 1906, P. ventilabrum, P. robusta and P. crassa at St. Td 90040106. The paucity of specimens of geodiids and ancorinids at St. Td 90040104 and Td 90040105 indicates that these two stations were situated on the fringe of an ‘‘ostur’’ area. The dominant species at these stations have morphologies which are quite different to that of geodiid and ancorinid species. The two Phakellia species consist of one to several fans on a common stalk, M. lingua has a lumpy, but very soft and loose structure, and P. crassa is similarly lumpy, but fragments very easily. At St. Td 90040106 large numbers of another astrophorid species, T. levis were sampled and may characterise another different type of astrophorid dominated bottom community. Thus the extent of the area with ‘‘ostur’’ can be estimated as starting at about St. Td 90040102 and ending at about St. Td 90040105. The westernmost haul of St. Td 90040102 (second haul) (Table 1) and the third haul of St. Td 90040105 where a specimen of G. barretti was sampled (Table 3) are considered to be at the edges of the ‘‘ostur’’ area. This implies that the ‘‘ostur’’ area stretches from 0610.57 0 W to

70

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98



Fig. 2. Geographic distribution of ‘‘ostur’’ in the northeast Atlantic. , own collections; n, areas contributed by Danish, Faroese, German, Icelandic and Norwegian biologists and fishermen; s, areas reported in Rezvoj (1928), Hentschel (1929), Filatova (1938), Blacker (1957), Koltun (1964), Dyer et al. (1984) and Henrich et al. (1992). Where stations are situated very close to each other, only a representative number of these are indicated.

0546.45 0 W in a west–east direction i.e., ca. 21 km. However, the largest accumulations of ‘‘ostur’’ sponges were sampled between St. Td 90040102 and Td 90040103, i.e., between 0610.57 0 W and 0600.05 0 W, a distance of 8.5 km. Geodia atlantica was not found along this transect, although it does occur in the area; for example at BIOFAR St. 901 just north of the transect at 6110.8 0 N, 0544 0 W, 242 m ca. 70 litres of G. atlantica were sampled with a shell dredge hauled for 20 minutes (Klitgaard et al., 1997). This serves as one more example of the locally varying composition of geodiid and ancorinid species in areas with ‘‘ostur’’. The hydrography of the large area supporting ‘‘ostur’’ on the southeastern plateau is dominated by Atlantic water and in situ temperature is likely to vary between 6.5 and 7.9 C. On the western and northern shelf slopes of the Faroes the ‘‘ostur’’ areas occur where there is a mixture of Atlantic water and Arctic Intermediate Water where in situ water temperatures are expected to range between 5.0 and 6.8 C. The large samples of I. phlegraei from the Iceland-Faroe Ridge and the Wyville Thomson Ridge were also collected where the bottom water was a mixture of Atlantic water and Arctic Intermediate water with a temperature about 4 C (Hansen & Østerhus, 2000; Nørrevang et al., 1994; Westerberg, 1991). 4.1.2. The Karmoy area Norwegian biologists reported to us that they had trawled varying quantities of sponges at some localities in the Norwegian Trench. The presence of sponges is, however, only routinely recorded in the log books when they dominated the catch (Table 2). From Table 2, it appears that trawl catches characterized as ‘‘sponge hauls’’ have been taken on the eastern slope in depths between 375 and 145 m, and mostly between 300 and 200 m. These samples have never been analyzed in detail with regard to the sponges and no

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

71

Fig. 3. Transect on the southeastern Faroese plateau, south of Suderø Bank. First and last stations of the transect are indicated. Each of the six stations consists of three hauls with triangular dredge (addition 1–3 on station numbers). The area indicated as ‘‘ostur’’ in ‘‘To´v’’ (Anonymous, 1988) is marked.

material had been preserved. The dominant sponges have been given the Norwegian name ‘‘sopp’’ meaning ‘‘mushroom’’ and are described as being white-yellow in colour, round or lumpy and up to half a metre in maximum dimension, and sometimes almost too heavy for a man to lift; this description fits well with G. barretti. Our sample localities were on the upper part of the eastern Trench slope at about 160 m depth west of Karmoy, an area where the in situ salinity is close to 35& and the temperature is about 5–7 C the year round (Tchernia, 1980; A. Johannessen, pers. commn). Two ‘‘sponge hauls’’ were collected in 1993 (Table 1). Both hauls were dominated by geodiids and S. ponderosus, but in differing relative quantities. Thus, at St. 237 similar numbers of G. barretti, G. atlantica and S. ponderosus were sampled, while at St. 242 G. barretti and S. ponderosus were abundant but G. atlantica was absent. Only a few specimens of G. macandrewi and I. phlegraei were collected (Table 4). In addition, several specimens of Thenea valdiviae Lendenfeld, 1906 were sampled notably at St. 242, but only a few Thenea muricata (Bowerbank, 1858) were collected from the two stations. Both trawls were well filled (Table 1) so the catches can be assumed to contain a representative sample of the size distribution of the dominant species. Since G. barretti is a tough species that withstands the sampling with relatively little damage, a size-frequency diagram has been constructed, combining data from the two samples (Fig. 4). At both sites the average maximum diameter was between 25 and 30 cm, with the largest specimens reaching 45–50 cm. No specimens <12 cm in diameter were found and very few were smaller than 16 cm in diameter. 4.1.3. The Trondheim Fjord Only sparse information exists on the sponge fauna of the Trondheim Fjord; the large astrophorids recorded hitherto are G. barretti, Geodia muelleri (Fleming, 1828), I. phlegraei, S. ponderosus, S. normani, and T. muricata (Arndt, 1913; Burton, 1930). G. muelleri has been reported from Røberg (Arndt, 1913);

72

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Table 3 Transect south of Suderø Bank on the southeastern Faroese plateau (compare with Fig. 3). Explanations are to be found at the bottom of the table St.no.

Td 90040101

Catch volume (litres) Substratum

1. haul c. 100 S, G, Bs

Geodia barretti G. macandrewi Isops phlegraei Stryphnus ponderosus Stelletta normani Thenea levis T. valdiviae Phakellia ventilabrum P. robusta Antho dichotoma Petrosia crassa Oceanapia robusta Mycale lingua

Few Few Few

Td 90040102

2. haul c. 100 S, G, Bs

Few Few Few

% sponges of total volume

c. 20%

St.no.

Td 90040104

Catch volume (litres) Substratum

1. haul c. 200 S, G, Bs

Geodia barretti G. macandrewi Isops phlegraei Stryphnus ponderosus Stelletta normani Thenea levis T. valdiviae Phakellia ventilabrum P. robusta Antho dichotoma Petrosia crassa Oceanapia robusta Mycale lingua % sponges of total volume

c. 20%

2. haul c. 100 S, G, Bs

3. haul c. 50 S, G, Bs

Few Few Few

c. 25%

Td 90040103

1. haul c. 300 G, Ss, Bs

2. haul c. 300 G, Ss, Bs

3. haul c. 300 G, Bs

1. haul c. 200 S, G, Bs

2. haul c. 200 S, G, Bs

3 ex. 3 ex. 2 ex. c. 210 l 1 ex.

4 ex. 1 ex. 1 ex. c. 150 l

8 ex. 1 ex. 1 ex. c. 90 l 4 ex.

2. ex. 4. ex. Few Few

2. ex. 2. ex. 1. ex. c. 100 l Few

Few Few Many

Few Few Few Few

Few Few Few Few

Few Few

Few Few

Few Few Few Few Few Few Few

>90%

>95%

>95%

Few Few Few 1 ex.

>95%

Few Few Few Few Few Few

>95%

>95%

Td 90040105 3. haul c. 75 S, G, Bs

1. haul c. 50 G, Bs

2. haul c. 20 G

3. haul c. 200 S, G, Bs 3. ex. c. 60 l

Td 90040106 3. haul c. 100 S, G, Bs

1. haul c. 150 S, G, Bs

2. haul c. 150 S, G, Bs

3. haul c. 20 G

c. 75 l

c. 45 l

c. 10 l

1. ex. 1. ex. 1. ex. 1. ex. Few Many Few Few Few

Few c. 30 l c. 20 l Few Few

Some >90%

>95%

Few Few

Few

Some Few

c. 5 l Few

c. 30 l c. 20 l

c. 25 l c. 15 l

c. 30 l c. 15 l

c. 5 l Few

c. 20 Few c. 20

Few

Few Few c. 20

Few Few

c. 45 Few Few

Few Few

Many

Few Few c. 5

>95%

>95%

>95%

>95%

>80%

>80%

>90%

Few c. 20 l Few

Three hauls with triangular dredge, each lasting ten minutes, were taken at each station. Number of specimens of dominating sponge species are shown for each haul. The quantity in some hauls is indicated as litres (l) or as the relative occurrence (few, some, many). S = sand, G = gravel, Ss = small stones, Bs = big stones.

however, this specimen could not be traced. Moreover despite intensive sampling in 1989 and 1994 at the same locality, as well as at numerous other localities throughout the fjord (Fig. 5, Table 1) no further specimens of G. muelleri have been found; so it is concluded that ArndtÕs specimen was probably misidentified (Tendal & Klitgaard, unpublished). The occurrence of geodiid sponges at various localities within the fjord is well known to local biologists, but a detailed investigation of their distribution has never been carried out. During this project most samples were taken in the large seaward basin but some were from the middle and inner basins (Fig. 5 and

Table 4 Number of specimens of astrophorid and hexactinellid species sampled at ‘‘ostur’’ stations: Karmoy (SW-Norway), Iceland and in the Denmark Strait. Explanations are to be found at the bottom of the table St.no.

G.b.

G.ma.

G.me.

NORWAY, the Karmoy area HM 237 49 HM 242 85 2 + Fr.

1

32

N-Iceland BIOICE 2022 BIOICE 2769

43

3 4 + Fr.

2 + many Fr. 7

the Denmark Strait 1 2 4 4 13 8 + Fr. 1 + Fr. 3 + Fr. 6 + Fr. 2 2

3

S.p.

St.n.

St.r.

49 124

T.v.

T.l.

14 94

T.m.

T.a

Sch.r

Tr.b

4 3 12

4

2 3

3

3

6

4 3

13 52 27 47 4

1 3 4 13

17

1

2 10 1 5

26 7 1

4 3

13

5

1 3 + Fr.

17*

131 316 15 3 4

277 411 286 5 8 226 536

1 30 7 5

I.p.p.

25

11 19

NW- and W-Iceland, the Denmark Strait BIOICE 2499 2 BIOICE 2501 13 BIOICE 2516 5 BIOICE 2518 23 BIOICE 2923 5 1 BIOICE 2926 4 BIOICE 2928 9 Ingolf 90 2 4 28 GREENLAND, 94PA0090001 94PA0090002 94PA0090009 94PA0090010 94PA0090019 94PA0090020 94PA0090043 94PA0090062 Ingolf 92

I.p.

Fr.

2 + Fr. Fr. 4 Fr. 6

159 132 18 3 3? 21 39

c. c. c. c. c. c. c. c.

4l 2l 5l 0.5 l 0.2 l 0.2 l 18 l 2l

c. 3 l 2 c. 6 l 1 c. 0.1 l 1 c. 0.5 l

c. c. c. 2 c. 3 c. c.

40 l 15 l 2l 3l 10 l 3l

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

ICELAND S-Iceland BIOICE 2292 Ingolf 78

G.a.

22*

G.b. = Geodia barretti, G.ma. = G. macandrewi, G.me. = G. mesotriaena, G.a. = Geodia atlantica, I.p. = Isops phlegraei, I.p.p. = I. phlegraei pyriformis, S.p. = Stryphnus ponderosus, St.n. = Stelletta normani, St.r. = S. rhaphidiophora, T.v. = Thenea valdiviae, T.l. = T. levis, T.m. = T. muricata, T.a. = T. abyssorum, Sch.r. = Schaudinnia rosea, Tr.b. = Trichasterina borealis. ? = probably Stelletta rhaphidiophora. (*) = about half the specimens are probably I. p. pyriformis, but it is difficult to identify small specimens to subspecies. The quantity of Thenea species and Schaudinnia rosea at some stations is indicated in litres (l). Fr. = fragments of specimens.

73

74

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Fig. 4. Size-frequencies of G. barretti sampled at St. nos. 237 and 242 at Karmoy, southwest Norway. The specimens of the two stations are marked differently. Only undamaged specimens are included.

Fig. 5. Localitites in the Trondheim Fjord from which species of Geodiidae have been sampled. The dotted lines indicate the Agdenes sill at the entrance, the sill at the island Tautra between the seaward and the middle basin and Skarnsund between the middle and the inner basin (Beitstadfjorden) respectively.

Table 1). In order to examine the bathymethric distribution it was intended to collect samples at different depth intervals. However, this was not always possible because of local conditions such as very steep rocky slopes, the presence of projecting shelves and strong currents. Table 5 shows that geodiids were collected

Table 5 Localities in the Trondheim Fjord at which species of Geodiidae have been sampled. Explanations are to be found at the bottom of the table Depth (m)

G.b.

Seaward Fjord Stjørnfjorden – – – Trondheimsleia Off Brettingneset Off Breidvikta˚a – Kalurdalsbukta Off Kinebbneset – Off Berganneset Off Esvikneset Off Røberg – – – Ma˚neskinnsviken – Off Geitaneset – Off Vorpneset Loddeberget – Aksnestangen – Off Omborneset – Rørvikgrunnen at Hindrem Munkholmen –

200–30 200–50 175–30 150–30 130–30 400–100 200–50 150–40 300–120 100–45 – 160–100 500–100 250–60 150–50 150–75 100–35 500–90 350–50 350–75 200–50 150–50 200–50 100–30 280–90 150–30 150–40 70–30 100–50 300–100 150–40

6 + Fr. 1 1 3 1 Fr. 1 + Fr. 1 + Fr. 1 1 + Fr. 1 + Fr. 2 2 Fr. 1 2 + Fr. Fr. 7 + Fr. 5 + Fr. 1 Fr. 1 4 1 2 5 + Fr. 1 + Fr. 1

Middle Fjord Nordviksundet – – Off Balvika –

300–70 250–25 200–25 225–50 150–40

5 + Fr. 3 + Fr. 2 + Fr.

Inner Fjord Skarnsundet, western slope

175–40

Fr.

G.m.

G.a.

I.ph.

S.p.

S.n.

T.l.

T.v.

1 Fr. Fr.

Fr. 1 + Fr.

Fr. 1 Fr. Fr.

1

Fr.

Fr.

Many Fr. Many Fr.

Many Fr. Fr.

1 2 + Fr.

Fr. 1 + Fr.

Fr. Fr. Fr. Fr. Fr.

7

1 + Fr. Fr.

2 Fr.

1 1

1

1 7 + Fr. Fr.

Fr.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Locality

1 1

Fr. 3

75 (continued on next page)

76

Locality

Depth (m)

G.b.

– Skarnsundet, eastern slope – – – – Beitstadfjorden, Fjordgrunnen Beitstadfjorden, Korsholmflua – – Beitstadfjorden, Off Galgneset

180–60 200–90 150–20 150–40 150–50 130–30 130–40 100–30 80–30 70–50 150–50

2 Fr. 3 + Fr. 1 3 + Fr. 2 1 2 + Fr. 1 + Fr. 1 + Fr. 2 + Fr.

G.m.

G.a.

Fr.

Fr. 1

I.ph.

S.p.

S.n.

T.l.

T.v.

1

1

Localities are indicated from the entrance of the seaward basin towards the inner basin (compare with Fig. 4 and Table 1). The number of sampled specimens of other astrophorid species at these stations are also shown. G.b. = Geodia barretti, G.m. = G. macandrewi, G.a. = G. atlantica, I.ph. = Isops phlegraei, S.p. = Stryphnus ponderosus, S.n. = Stelletta normani, T.l. = Thenea levis, T.v. = T. valdiviae. Fr. = fragments of specimens.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Table 5 (continued)

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

77

from depths ranging between 500 and 30 m in the seaward basin, between 300 and 25 m in the middle basin and between 180 and 20 m in the inner basin. The majority were sampled off forelands or in narrow parts of the fjord such as Nordviksundet and Skarnsundet. Despite the sampling efforts being less intensive in the middle and inner basins it seems possible to discern a gradient in the distribution of the geodiid species. G. barretti was the most frequently occurring species, being present at almost all stations in the three basins (Table 5). G. atlantica and I. phlegraei were also frequently represented in the samples from the seaward basin. But only a few fragments of I. phlegraei were collected in the middle basin and no evidence of its presence in the inner basin was found. G. atlantica was not found in the middle basin and only a single specimen and a fragment were collected at Skarnsundet the sill between the middle and the inner basins. One fragment of G. macandrewi was taken in Skarnsundet (Table 5). Throughout the fjord more than 70 specimens of G. barretti were taken. Most specimens had maximum diameters of 10–25 cm, the average 15–20 cm. The largest specimen was nearly 40 cm, but the size of the gear used may have excluded any larger ones. Small specimens were especially looked for, but very few were found with diameters below 10 cm, and only two were smaller than 5 cm. The mean temperature and salinity in the three basins are influenced by the exchange with the sea and by variations in the fresh water supply from the large rivers (Jacobson, 1983). Below the surface layer the water masses are usually replaced twice a year. From February until May–June, there is an inflow of deep water of high salinity (>34&) and a temperature of 6.5–7.4 C that replaces the bottom water in all three basins. The replacement of bottom water in Beitstadfjorden lags a little behind that of the two other basins because of the narrowness of Skarnsundet. In late summer, there is an inflow at intermediate depths of 20–70 m depth of 32–34& coastal water which mixes with the bottom water in the basins, causing the 34& isohaline to deepen in all three basins. The ‘‘winter cold wave’’, represented by the 7 C isotherm, reaches a depth of 125 m in the seaward basin, 270 m in the middle basin and 80 m in Beitstadfjorden, reaching its maximum depth in all three basins between March and April. Later in the year the upper layers are warmed so that the 8 C isotherm sinks reaching its maximum depth of 80–90 m during October and December (Jacobson, 1983). The fjord has semidiurnal tides with an average range of 1.8 m (Wendelbo, 1970). Tidal currents up to 100 cm/s have been measured over the Agdenes sill at 115 and 315 m. At two localities over the Tautra sill, tidal currents of 39 and 70 cm/s, respectively, were measured, indicating that there are significant, local topographically induced, amplifications. On the eastern side of Skarnsundet tidal currents of 78 cm/s have been measured at 10 m depth and on the western side of 104 cm/s at 80 m depth; the strength of these tidal currents contributes significantly to the mixing processes in the intermediate and deeper water masses (Jacobson, 1983). 4.1.4. The Koster sound The astrophorids found are G. barretti, I. phlegraei, S. ponderosus and S. normani (Alander, 1942; Ja¨gerskio¨ld, 1971; own obs.). Alander (1942) stated that all four species are common; we support his view for the first three, but S. normani was less frequently recorded than the others during investigations by OST in 1974–1977. G. barretti occurs at numerous localities at depths of 50–220 m. On the southern slope of the island of Krugglo¨, it forms a monospecific assemblage at 150–60 m, with up to 20 specimens being caught in the small dredge, hauled for 5–10 min. Most specimens were rounded and 15–25 cm in diameter; but larger specimens 40–50 cm in maximum diameter tended to be flattened and of irregular form. At deeper localities, such as Bjo¨rns Rev, which seems to be a kind of ridge protruding from the bottom of the sound, and east of the Island of Ramso¨ and a little further to the south, off Ulvillarna (a group of rocks), all four species were caught at 220–150 m, sometimes in concentrations that filled up the dredge within only a few minutes. Mass occurrences at such relatively great depths seem only to occur on the western flank of the sound, perhaps an indication of differences in current conditions. I. phlegraei, S. ponderosus, and

78

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

S. normani attain sizes of about 20 cm in diameter, but despite samples having been taken at all times of the year, no interseasonal or interannual differences in size have been noted. Specimens smaller than about 5 cm in diameter of all four species are rare and are mostly specimens of I. phlegraei. As in the deep parts of Skagerak, the salinity at 220 m is close to 35& the year round, and the temperature between 5 and 8 C (Hansson, 1976). 4.1.5. The Skagerak area ‘‘Ostur’’ have been recognized at both the western and the eastern end of Skagerak (Karmoy and Koster Sound, respectively). In the areas between, there are few records for the northern shelf edge. Alander (1942, p. 9 & 87) states that at depths between 100 and 300 m off Jomfruland and Finsba˚ene (Norwegian southcoast, between 938 0 E and 950 0 E), ‘‘. . .enormous quantities of, e.g., Geodia and Stelletta (Dragmastra) are found.’’ G. barretti and S. normani are specifically recorded from the area, together with a number of other species which often occur with the astrophorids in the North Atlantic mass sponge localities. Exceptions are the Thenea species, which have not been recorded from the Skagerak proper. Only T. muricata has been recorded in the eastern part around 715 0 E, at depths of 140–313 m (Steenstrup & Tendal, 1982; ZMUC collection). 4.1.6. Northern Norway to Spitzbergen Mass occurrences of astrophorid sponges and/or tetractinellid sponge spicules have frequently been reported as being widely distributed in the western Barents Sea, from northern Norway to west of Spitzbergen, at depths between 150 and 350 m (Appelo¨f, 1912; Blacker, 1957; Dyer et al., 1984; Erekovsky, 1993, 1995; Filatova, 1938; Koltun, 1970; Rezvoj, 1928; Zenkevitch, 1963). Whenever specific names have been mentioned, Geodia is always included, and in many cases the species has been identified as G. barretti. However, not only is G. barretti widespread in the western Barents Sea, but so are G. macandrewi, I. phlegraei and I.p. pyriformis (Erekovsky, 1993; Hentschel, 1929; Koltun, 1966), so not all authors may have distinguished all these species. S. ponderosus and S. normani are also widely distributed, as is T. valdiviae although it is sometimes treated as T. muricata. Fishermen have reported that several tons of white sponges up to about 1 m in diameter have been caught in some areas, presumably these have been mainly G. barretti, but no such large catch of sponges has ever been fully worked up. Filatova (1938) reported finding enormous amounts of sponges, mainly G. barretti and T. muricata off the north Norwegian coast, in the central parts and on the slopes of the Northcape and Fugloy Banks, at depths of 150–250 m (compare with Norwegian Fishery Chart, 552). Zenkevitch (1963), elaborating on the reports by Filatova and others, stated that the mass accumulations of sponges occurred on a sandy and sandy-silty bottom, with good water movement. The sponges contributed 95–98% to the total biomass sampled, in extreme cases amounting to 5–6 kg/m2. The bottom temperature in the area never falls below 2 C and the salinity is about 35& (Zenkevitch, 1963). Relatively high sponge biomasses are noted by Erekovsky (1995) along the western shelf of the Barents Sea and west of Spitzbergen. Blacker (1957, p. 28) reported that ‘‘At some stations at the western end of the Bear Island Channel several tons (of G. barretti) at a time have been caught in trawl hauls.’’ Further to the north he found G. barretti to be very common. Most of the catches came from about 180 to 360 m depth, along the shelf and bank edges, within a temperature range 1–4 C. Dyer et al. (1984) later confirmed BlackerÕs results. North of Spitzbergen, at about 1000 m depth, rich assemblages of sponges have been reported from two adjacent stations (at 8120 0 N, 2030 0 E and 8120 0 N, 190 0 E) (Schulze, 1900; Hentschel, 1929). There the bottom sediment consisted of a thick, muddy mat of tetractinellid and hexactinellid spicules. The dominant species were G. mesotriaena, I.p. pyriformis, Stelletta rhaphidiophora Hentschel, 1929; T. valdiviae and the hexactinellids Schaudinnia rosea (Fristedt, 1887), Trichasterina borealis Schulze, 1900; and Scyphidium sep-

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

79

tentrionale Schulze, 1900. The bottom temperature in this area is about
1 C and the salinity 34.9& (Stro¨mberg, 1989). 4.1.7. South Iceland Icelandic biologists have supplied us with data of very large catches of sponges from the Reykjanes Ridge (Table 2). Half of the catches were taken from the top of the ridge at depths of between 900 and 1000 m. One catch was from the upper part of the western flank at 1064–1210 m and the two largest catches of about 20,000 kg of sponges or more were from about 1200 to 1300 m on the eastern flank. The sponges were not identified and no material was kept. The same name is used to describe the sponges as at the Faroe Islands, that is ‘‘osti’’ = ‘‘cheese’’. A single sample characterized as ‘‘ostur’’ was taken during the BIOICE programme from the summit of the Bjørn Ridge, a ridge which lies parallel to the Reykjanes Ridge, at 1204 m depth (BIOICE 2292) (Table 1); two complete specimens and many broken fragments of G. atlantica were kept from this station (Table 4). St. 78 of the Danish Ingolf Expedition (1896) was on the eastern slope of the Reykjanes Ridge to the south of the ‘‘ostur’’ localities reported by Icelandic biologists (Fig. 2, Tables 1 and 2). The material retained from this station included seven specimens of G. atlantica, several specimens of G. mesotriaena and I. phlegraei and a single specimen of G. barretti (Table 4). These two samples collected during BIOICE and the Ingolf Expedition imply that the large catches from the summit of the Reykjanes Ridge were probably dominated by geodiids. Coastal water of varying temperature and of a salinity <34& dominate the shelf down to depths of about 100 m during summer and autumn. The Icelandic slope is dominated by water of mixed origin but mainly Atlantic; with salinities close to 35&, and temperatures in the range 4.5–8 C. This watermass extends to 800–1400 m depth, depending on the locality; in general, it extends deeper on the western side of the Reykjanes Ridge than on the eastern (Hansen, 1985; Hansen & Østerhus, 2000; Malmberg & Kristmannsson, 1992; Thomsen, 1938). 4.1.8. North and west Iceland One sample characteristic of ‘‘ostur’’ has been taken from northeast of Iceland at a depth of 325 m on the flank of a small bank (BIOICE 2022, Table 1). The dominating geodiid species were G. mesotriaena and I.p. pyriformis (Table 4), and other species represented were S. rhaphidiophora and T. valdiviae. North of Iceland, a sample of ‘‘ostur’’ has been taken on the slope of a seamount which is part of the Kolbeinsey Ridge at a depth of 519 m (BIOICE 2769, Table 1). This sample was also dominated by G. mesotriaena and some specimens of S. rhaphidiophora were also present (Table 4). Northwest of Iceland four samples of ‘‘ostur’’ (BIOICE 2499, 2501, 2516 and 2518, Table 1) were collected in the northern part of the Denmark Strait Channel at depths ranging between 629 and 749 m. All four samples were dominated by G. mesotriaena and I.p. pyriformis. S. rhaphidiophora was represented in all four samples, S. rosea in three and T. borealis at BIOICE 2516. Several specimens of Thenea species were present in the sample at St. 2501 (Table 4). To the west of Iceland three samples of ‘‘ostur’’ were collected; two on the western and one on the eastern flank of the southern part of the Denmark Strait Channel at depths of 540, 704 and 678 m, respectively (BIOICE 2923, 2926 and 2928, Table 1). Specimens of G. barretti were collected at all three stations. A single specimen of I. phlegraei was collected at BIOICE 2926. Several specimens of I.p. pyriformis were in the sample from St. 2923, together with a number of S. normani and an individual of G. macandrewi (Table 4). St. no. 90 of the Ingolf Expedition was situated on the southern flank of the Denmark Strait at a depth of 1070 m (Table 1). The material preserved from this station includes specimens of both I. phlegraei and I.p. pyriformis, G. mesotriaena, G. barretti, G. macandrewi and G. atlantica (Table 4). At all stations north of Iceland bottom water temperatures were
0.50 to
0.40 C and salinities were 34.90&. According to the definitions of watermasses of Malmberg and Kristmannsson (1992) and Blindheim, Buch, Fogelqvist, Tanhua, and Østerhus (1996) the bottom watermasses at all stations were variants

80

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

of Artic Intermediate Water. BIOICE 2769 was in Norwegian Sea Arctic Intermediate water (
0.5 < T < +0.5 C; 34.87 < S < 34.90&). Whereas the stations in the northern part of the Denmark Strait Channel and also BIOICE 2022 from northeast of Iceland were in Iceland Sea Arctic Intermediate water (T < 2 C; S 34.7–34.9&). BIOICE 2928 on the southeastern part of the Denmark Strait Channel is in the Atlantic water of the Irminger Current (T 5–7 C, S 35.05–35.10&), which also influenced St. 90 of the Ingolf Expedition (4.4 C, Table 1). BIOICE 2925 on the southwestern slope of the channel is in the Denmark Strait Overflow water (T < 1 C, S 34.8–34.9&), and BIOICE 2923 is similarly mainly influenced by this watermass. 4.1.9. The Denmark Strait The occurrence of accumulations of sponges at some localities of the Denmark Strait is well known to Danish fishery biologists conducting survey cruises in the area. Several cruise leaders have supplied us with data on localities (Table 2) and some samples of the most frequently occurring sponge species have been kept. Sponge accumulations were also encountered during R/V Walther Hervig cruise no. 51, ‘‘Overflow-expedition’’, in 1973, and the position of large catches were recorded (Table 2). No material was kept but the dominant sponges were described as ‘‘Kohl’’, the German name for cabbage. Substantial data comes from eight ‘‘sponge hauls’’ ABK examined during the cruise in 1994 by R/V Paamiut (Table 1). Localities of ‘‘ostur’’ regions around southeastern Greenland are illustrated in Fig. 6. The first four stations listed under Greenland in Table 2 (St. 92PA0160001, 90MA0200057, 92PA0160002 and 89SI0240055) were situated on the Greenland shelf, between the eastern slope of East Bank and the western



Fig. 6. Topographical map of the Denmark Strait (as published in Larsen, 1983). , ‘‘ostur’’ stations where more than 100 litres of astrophorid sponges were sampled; [circle half filled at bottom], stations where geodiid sponges were present but in quantities less than 100 litres and s, stations where no geodiid sponges were collected.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

81

slope of the Denmark Strait Channel, at depths of 300–400 m. Specimens kept from St. 92PA0160002 included I.p. pyriformis (4), G. mesotriaena (1), T. valdiviae (1) and S. rosea (2). No material was retained from St. 90MA0200057 but a photograph taken of the catch by the cruise leader (Dr. Klaus Lehmann) shows numerous specimens of I.p. pyriformis, G. mesotriaena and G. macandrewi. St. 94PA0090001 and 94PA0090002 were from the same area and depth (Table 1), both samples were dominated by I.p. pyriformis and G. mesotriaena, together with a few specimens of G. barretti, G. macandrewi and large numbers of S. rhaphidiophora and some T. valdiviae, T. muricata and S. rosea (Table 4). St. 92PA0160046 was situated between the western slope of East Bank and the eastern slope of the Kangerdlugssuaq Channel at a depth of about 200–250 m (Table 2), but no material was kept. Stations 94PA0090009 and 94PA0090062 were situated on the western flank of East bank, at depths of 441–440 and 467–448 m, respectively (Table 1). Both samples were dominated by I.p. pyriformis, with G. barretti, G. mesotriaena, S. ponderosus, Stelletta rhapidiophora, T. valdiviae, T. muricata, S. rosea and especially G. macandrewi also represented in the samples (Table 4). At both stations several litres of muddy tetractinellid spicules were collected. Station 94PA0090010 at a depth of 241–226 m in the same region (Table 1) contained no specimens of I.p. pyriformis. The sample was characterized by G. barretti and a few specimens of G. macandrewi, G. mesotriaena, S. ponderosus, S. rhapidiophora, T. valdiviae, T. muricata and S. rosea (Table 4). Three stations (Sts R/V WH 637/73, 89SI0240080 and 89SI0240075, Table 2) were situated between the southeastern slope of Strede Bank and the western slope of the Denmark Strait Channel, at depths of between 320 and 520 m. No material was preserved from any of these stations. However, the sample from St. 94PA0090043, which was located in the same area on the eastern slope of Strede Bank at about 380 m (Table 1), was dominated by I.p. pyriformis, with numerous T. valdiviae and some G. mesotriaena, S. rhapidiophora, T. muricata and S. rosea (Table 4); some muddy tetractinellid spicule mats were also present. No material was kept from St. R/V WH 642/73 on the southern slope of the Denmark Strait south of Dohrn Bank at a depth of ca. 970 m. The remaining Greenland stations listed in Tables 1 and 2 were all located southwest of the Kangerdlugssuaq Channel. Sts 92PA0160052 (Table 2) and 94PA0090020 were close to each other on the northeastern slope of the Gauss Bank at a depth of ca. 300 m and 94PA0090019 was on the northwestern slope of this bank at about 360 m (Table 1). Two specimens of I.p. pyriformis as well as one S. ponderosus were kept from St. 92PA0160052. Some specimens of I.p. pyriformis were also found at St. 94PA0090020 in addition to some specimens of G. barretti and a few G. macandrewi, S. ponderosus, Stelletta sp., T. valdiviae, T. levis and S. rosea. One specimen of G. atlantica was present in the sample, the only specimen that has been found in the Denmark Strait proper. At St. 94PA0090019 a very large specimen of G. barretti weighing 21.5 kg, with a diameter of 42 cm, was taken together with some smaller specimens and a few G. mesotriaena, I.p. pyriformis, S. ponderosus, T. valdiviae, T. muricata and S. rosea (Table 4). St. R/V SM 104 was on the southern slope of the Denmark Strait, east of the Gauss Bank at ca. 700 m (Table 2); one G. barretti was preserved from this station. The Stations R/V WH 651/73, 652/73, 653/73 and 654/73 constituted a transect down the southwestern slope of the Denmark Strait, southeast of the Gauss Bank starting at a depth of 500 m and finishing at about 1500 m (Table 2). Table 2 shows that the quantities of sponges collected increased from ca. 20 baskets at 500 m to more than 50 baskets at 1500 m. Unfortunately, no material was kept from any of these stations. St. 92 of the Ingolf Expedition was located in this area at about 1800 m (Table 1) and specimens of both I. phlegraei and I.p. pyriformis, G. mesotriaena and a few fragments of G. atlantica were preserved from the sample (Table 4). St. R/V SM 67 was located on the southwestern slope of Kap Dan Bank near the Greenlandic Coast at a depth of about 220 m and one specimen of G. barretti, G. macandrewi, G. mesotriaena and I.p. pyriformis were preserved from this station. Because large numbers of undamaged specimens, including small ones, were measured from the catches on R/V Paamiut in 1994, it has been possible to construct size-frequency diagrams for I.p. pyriformis and

82

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

G. mesotriaena from four of these stations (Figs. 7 and 8). The mean sizes of I.p. pyriformis sampled at St. 94PA0090001 and 94PA0090002 were similar 9.2 ± 3.7 and 8.3 ± 3.4 cm, respectively, but much smaller at St. 94PA0090043, 4.1 ± 3.7 cm, and St. 94PA0090062, 3.7 ± 2.3 cm (Fig. 7). The average size of G. mesotriaena from Sts 94PA0090001 and 94PA0090002 is similar, 5.1 ± 2.7 and 4.3 ± 2.7 cm, respectively (Fig. 8),

Fig. 7. Size-frequencies of I.p. pyriformis at four stations in the Denmark Strait. Only undamaged specimens are included. (a) St. no. 94PA0090001, n = 277 specimens. (b) St. no. 94PA0090002, n = 411 specimens. (c) St. no. 94PA0090043, n = 226 specimens. (d) St. no. 94PA0090062, n = 536 specimens.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

83

Fig. 8. Size-frequencies of G. mesotriaena at two stations in the Denmark Strait. Only undamaged specimens are included. (a) St. no. 94PA0090001, n = 128 specimens and (b) St. no. 94PA0090002, n = 322 specimens.

and about half the average size of I.p. pyriformis at these stations. The samples indicate the presence of relatively old, established geodiid populations between the eastern slope of East Bank and the western slope of the Denmark Strait Channel at depths of about 300 m (Sts. 94PA0090001 and 94PA0090002). While the populations of I.p. pyriformis on the eastern slope of Strede Bank at 380 m (St. 94PA0090043) and between the western slope of East Bank and the eastern slope of the Kangerdlugssuaq Channel at 460 m (St. 94PA0090062) seem to be dominated by younger, smaller specimens. The majority of the ‘‘ostur’’ stations (Tables 1 and 2) were in the Iceland Sea Arctic Intermediate water in the Denmark Strait (T < 2 C; S 34.7–34.9&) (Blindheim et al., 1996). Along the transect down the southwestern slope of the Denmark Strait the stations WH 651, WH 652, WH 653 and WH 654 had bottom temperatures of 7.4, 3.3, 3.0 and 1.4 C, respectively, indicating the intrusion of Atlantic water via the Irminger Current at the shallower stations, and an increasing influence of the Denmark Strait Overflow water at the deeper stations. Similarly, the bottom temperature at St. 92 of the Ingolf Expedition at 1838 m was 1.4 C, indicating the influence of the Denmark Strait Overflow water. 4.1.10. Off east greenland In the Greenland Sea, north of the Denmark Strait, the sponge fauna is relatively well known in three restricted areas. In 1930–1932, Norwegian expeditions visited some of the fjords and parts of the coast between 72N and 7430 0 N. Sponges were recorded from 32 localities from depths ranging from 14 to 432 m. Although some of these samples were rich in species, especially between 135 and 200 m depth, none of the data give the impression there were mass occurrences of large-sized species (Burton, 1934). In 1994, a German expedition worked on the outer shelf and the slope along the 75N. It sampled with an Agassiz trawl at different depths between 200 and 2700 m and large occurrences of sponges were found at three stations between 750 and 800 m. On a bottom of matted sponge spicules consisting predominantly

84

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

of hexactinellid spicules mixed with some tetractinellid spicules, the dominating larger species were G. mesotriaena, I. p. pyriformis, S. rhaphidiophora, T. valdiviae, with the hexactinellids S. rosea, T. borealis, S. septentrionale and Asconema setubalense Kent, 1870 (D. Barthel, pers. comm.; det. OST). The temperature near the bottom at that depth is always just below 0 C and the salinity 34.9& (Buch, 1991). To the southeast, at 7330 0 N, 910 0 W, investigations on the seamount Vesterisbanken showed sponges and spicule mats to be common from the top at 133 m depth down to about 260 m (Henrich et al., 1992). The most common species were reported to be G. sp., Stelletta sp., Thenea cf. muricata, and S. rosea. The bottom temperature range given is 0–1 C and the salinity around 34.9&. Russian expeditions worked at different depths in the Fram Strait in 1955–1958. At least at one station (about 78N, 6W), the trawl brought up large amounts of sponges from a depth of 1000 m on a bottom of gravel mixed with sand and mud (Koltun, 1964). The larger species were G. mesotriaena, I.p. pyriformis, S. rhaphidiophora, Thenea abyssorum Koltun, 1959a, 1959b; with the hexactinellids T. borealis and Caulophacus arcticus (Hansen, 1885). The temperature near the bottom was
0.4 C.

5. Discussion 5.1. Collection methods Information on ‘‘ostur’’ has been compiled from several different sources. The most detailed information on taxonomic composition and relative abundance has been acquired from the personal experience of the authors participating on the cruises. The sampling gears used on these various cruises (most often a triangular dredge, rectangular dredge and detritus sledge) have, however, brought up low quantities of sponges and may have failed to collect very large specimens. The use of an Agassiz trawl as one of the standard sampling gears on BIOICE cruises increased both quantity and size of sponges in the catches, but the coarseness of the mesh of the trawl (mesh diameter ca. 40 mm) prevented proper sampling of small specimens. The most representative samples of ‘‘ostur’’ are the trawl hauls taken at the Faroe Islands during the BIOFAR programme (Fig. 2), at Karmoy (SW Norway) in 1993 during a R/V Ha˚kon Mosby cruise, and in the Denmark Strait in 1994 during a R/V Paamiut survey cruise. The bottom trawl was hauled for one hour both at the Faroe Islands and in the Denmark Strait, and for 20 min at Karmoy. A short hauling period as compared to commercial trawling gives more accurate position data on the ‘‘ostur’’ areas, although not as accurate as when sampling with dredges or sledges, which are mostly hauled for 10–20 min. Sponges of very different sizes can be represented in the same trawl catch, as was convincingly seen in the samples taken in the Denmark Strait in 1994, where large numbers of young geodiids with diameters of 0.5– 1.0 cm were obtained at some stations. The smaller samples collected with the triangular dredge and rectangular dredge in the Trondheim Fjord and in the Koster area did not enable size-frequency diagrams to be compiled. Another problem is that some of the ‘‘ostur’’ species fragment very easily. G. atlantica, S. ponderosus and to some degree I. phlegraei are almost always fragmented when sampled no matter what gear was used and how long it was towed. An exception was found in the Denmark Strait where I.p. pyriformis were on average of a smaller size and more robust than the Faroese and Norwegian specimens of I. phlegraei, the majority being recovered entire. G. barretti, G. macandrewi and G. mesotriaena are of a more firm consistency and seldom fragment during sampling. However, too few specimens of G. macandrewi were collected to compile size-frequency diagrams. Data on ‘‘ostur’’ given by different biologists are all based on trawling (Table 2). The duration of the hauls has been noted for most areas, being between 20 min for the Karmoy area and one hour for the Reykjanes Ridge, and either one hour (the Greenland Institute of Natural Resources) or 30 min (R/V Walther Herwig ‘‘overflow 73’’ cruise) in the Denmark Strait. Thus, the position data on ‘‘ostur’’ obtained from these sources are relatively precise. However, samples of sponges were seldom kept from these trawl catches

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

85

so their taxonomic composition is unknown. In some cases, it has, however, been possible to deduce the probable composition from other samples in the same area. In addition, a hint of the identity of the dominating species comes from the descriptive name given to them by fishermen and fishery biologists of different nationalities. Names such as ‘‘ostur’’ and ‘‘osti’’ (= cheese), ‘‘sopp’’ (= mushroom), ‘‘Kohl’’ (= cabbage) and ‘‘duff’’ (= stiff flour pudding) all seem to refer to the size, form, consistency and smell of geodiid sponges. There is traditional knowledge among fishermen, that very large areas with ‘‘ostur’’ occur in the western part of the Barents Sea, and we have been informed about a number of such areas (Table 2). These data are, however, based on commercial trawling when each haul lasts for several hours and no sponges are ever kept from these catches. Experience from the Faroe Islands and the Denmark Strait indicates that ‘‘ostur’’ does not constitute very large, coherent areas but is patchily distributed depending on the local topography and hydrography (Fig. 9). Thus since trawling for several hours covers long distances, reports of very large catches of ‘‘ostur’’ amounting to several tons reported from the Barents Sea probably results from a number of smaller ‘‘ostur’’ patches within the trawled area rather than an even distribution of the sponges. 5.2. Distribution All the available data on ‘‘ostur’’ in the northeast Atlantic is combined in Fig. 2. It shows that the distribution of accumulations of large-sized astrophorid sponges occupies two bands related to the flow paths of the Norwegian Atlantic Current and the Irminger Current and their main branches. These two ‘‘ostur’’ bands are not continuous but represent series of patches whose presence depends to a great extent on the local topography. Thus, the majority of the areas of ‘‘ostur’’ reported here, are found on the shelf plateau close to the shelf break (the Faroe Islands, the Karmoy area, and the western Barents Sea), on the upper

Fig. 9. Bottom photograph from an area with ostur southeast of The Faroes at 245 m depth (BIOFAR St. 649; Nørreveang et al., 1994). J. Gutt photo. The picture covers about 0.8 m2 bottom area. Several large demosponge species are seen on a sandy gravelbottom: the white round lump, G. barretti; the irregular white branches, P. crassa; the dark brown column, S. ponderosus, with orangecoloured flakes of Aplysilla sulphurea; and the flake-formed Phakellia sp.

86

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

slope (the Faroe Islands, the Karmoy area, and East Greenland), on the slope of the banks (the Faroe Islands, the western Barents Sea, and the Denmark Strait), on ridges (the Reykjanes Ridge), and on the rocky sides of fjords especially off forelands and in narrow straits (the Trondheim Fjord, and the Koster area). 5.2.1. Banks and plateau edges About 700 samples of benthic macrofauna (>1 mm) were collected during the BIOFAR cruises in 1987–1990 at depths ranging between 100 and 1200 m using different types of sampling gear (Nørrevang et al., 1994). A number of these samples were taken in areas marked as ‘‘ostur’’ in ‘‘To´v’’ (Anonymous, 1988) or indicated as such by trawler captains, but some previously unreported areas with ‘‘ostur’’ were discovered. A total of 76 BIOFAR samples together with information used in charting show that areas with ‘‘ostur’’ are mainly situated close to the shelf break at depths between 200 and 500 m. The dominant species in these areas were G. barretti, G. atlantica and S. ponderosus. Large numbers of I. phlegraei were recorded on the southern slope of the Iceland-Faroe Ridge close to the Faroes and on the Wyville Thomson Ridge. G. macandrewi was also present but not in large numbers (Klitgaard et al., 1997). Other commonly occurring large-sized sponges in these areas are listed in Table 6. In ‘‘To´v’’ (Anonymous, 1988) ‘‘ostur’’ is shown to occur on the southeastern part of the Faroese plateau, south of the Suderø Bank at depths between 200 and 300 m, a large area well known to Faroese fishermen (Fig. 3). One trawler captain knew of a continuation of the area down the southeastern shelf edge into depths from ca. 250 to 410 m, and several others as well as ‘‘To´v’’ (Anonymous, 1988) indicate the presence of narrow belts of ‘‘ostur’’ along the 300 and 400 m isobaths and in the depth interval of 250–350 m (Klitgaard et al., 1997). The transect made by the present authors across the area of ’’ostur’’ on the southeastern Faroese plateau confirms the rather sharp demarcation of the area as shown in ‘‘To´v’’, demonstrating, together with the BIOFAR sampling, that ‘‘ostur’’ is not found all over the southeastern plateau but occurs in local concentrations. Frederiksen, Jensen, and Westerberg (1992) reported the presence of large banks of the scleractinian coral Lophelia pertusa in the same general area. Two different mechanisms were proposed by these authors to explain the presence of dense concentrations of coral banks on the southeastern plateau and on the shelf slope all around the Faroes. These mechanisms have been extended in Klitgaard et al. (1997) to apply also to the areas with ‘‘ostur’’. According to this theory, accumulations of large suspension feeders, such as L. pertusa and ‘‘ostur’’, show a tendency to aggregate near the shelf break in regions with a critical slope where the bottom slope matches the slope of propagation of internal tidal waves. The causal link is thought to be an increase in the supply of food related to the incidence of internal waves, which results in resuspension. Fig. 6 shows the distribution of three categories of trawl stations in the Denmark Strait: ‘‘ostur’’ stations (>100 litres of geodiid sponges in the trawlcatch), stations where geodiids were present in the catch but not in large quantities (<100 litres in the trawlcatch), and stations without geodiids. The ‘‘ostur’’ stations comprise all known information available at present (Tables 1 and 2). The other two categories of stations are based on information gathered by ABK on the cruise in 1994 and by the cruise leader (Dr. Per Kanneworff) who, during a survey cruise in 1992 studying shrimp arranged by the Greenland Institute for Natural Resources, noted the quantity of geodiids present at each station. It appears from Fig. 6 that no geodiids occur on top of the large Strede Bank, whereas stations with only a few geodiids are distributed at the periphery of the bank, and the ‘‘ostur’’ stations are found on the slope. At all stations in the Kangerdlugssuaq Channel and on the Greenlandic shelf near the coast the hauls contained either no geodiids or only a few. The ‘‘ostur’’ stations were either on the slopes of the banks or on the northern slope of the Denmark Strait Channel. It was not possible to obtain detailed information about the local distribution of ‘‘ostur’’ on the banks off northern Norway. The little which is known (Filatova, 1938; Zenkevitch, 1963) points to the presence of large concentrations near the edge and on the sides. Both Blacker (1957) and Dyer et al. (1984) found very

Table 6 Dominant sponge species on ‘‘ostur’’ in different geographic areas. Explanations are to be found at the bottom of the table Order

Geodia barretti G. macandrewi G. mesotriaena G. atlantica Isops phlegraei I. phlegraei pyriformis Stryphnus ponderosus Stelletta normani S. rhapidiophora Thenea valdiviae T. levis T. muricata Phakellia ventilabrum P. robusta P. rugosa P. bowerbanki P. arctica Tragosia infundibuliformis Mycale lingua Lissodendoryx complicata Antho dichotoma Oceanapia robusta Petrosia crassa Schaudinnia rosea Trichasterina borealis Schyphidium septentrionale Asconema setubalense

Norway

The Faroe Islands

Karmoy

The Trondheim Fjord

X X

X X

X X

X X

X X

X X

X

X X

X X

X

X X X X X X

X X

X X X X

X X X

X X

X X

X X

X X

X

X X X

X

Greenland The Denmark Strait

East Greenland

X X X X X X X

X

X X X X X X X X X X

X

X

X X

X

X

X X

X X X X

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Astrophorida – – – – – – – – – – – Axinellida – – – – – Poecilosclerida – – Haplosclerida – Hexasterophora – – –

Species

Included are the most commonly occurring large-sized species of other Demospongiae orders and Hexactinellid subclass in addition to the astrophorid species.

87

88

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

large concentrations of G. barretti on the slope at 180–350 m depth on the northern side of the entrance to the Bear Island Channel. Thus, the available data indicate a similar distribution pattern of ‘‘ostur’’ on banks and plateau edges around the Faroe Islands, off northern Norway and in the Denmark Strait. Because of the well described topography, detailed knowledge of hydrography, and the existence of numerous samples, the Denmark Strait would seem well suited as an area for further testing of ideas on the influence of internal tidal mixing processes on the distribution of ‘‘ostur’’. 5.2.2. Fjords Geodia barretti is the most frequent species in the Trondheim Fjord, in the Koster area and it is also found in large quantities at Karmoy (Tables 3 and 5). The average sizes of the specimens sampled at St. 237 and 242 at Karmoy are almost identical, 28.9 ± 8.7 and 27.0 ± 7.9 cm, respectively, with the largest specimens measuring 45 and 46 cm (Fig. 4). The sponges were sampled with a bottom trawl with a coarse mesh size (40 mm) cod end so the smallest specimens might be underrepresented. However, the smallest specimen collected measured 12 cm, which was too big to be missed by the sampler or to slip through the meshes. Thus, the data indicate a population of rather large-sized specimens of G. barretti occurring west of Karmoy, which is also consistent with the description given by Norwegian biologists of specimens of ‘‘sopp’’ up to about half a metre or larger. The sampling in the Trondheim Fjord and the Koster area was done with a triangular dredge/rectangular dredge so no large samples of G. barretti were obtained making it impossible to depict the size-frequency. However, 71 unbroken specimens were sampled in the Trondheim Fjord, of which only seven were larger than 27 cm in maximum diameter, the largest specimen being 39 cm in diameter; 16 specimens were <12 cm in maximum diameter, and the smallest specimens were 3 cm in diameter. Similarly, in the Koster area, few specimens with a maximum diameter >30 cm were found, and the majority of specimens measured 15–20 cm. Thus, there is a tendency for the average size of G. barretti to be smaller in the Trondheim Fjord and the Koster area, compared to the Karmoy area. Isops phlegraei is represented in samples collected at Karmoy, in the Trondheim Fjord and in the Koster area but was not as numerous as G. barretti (Tables 3 and 5). This species fragments rather easily during sampling so only a few of the specimens collected could be measured. However, specimens from Trondheim Fjord were generally smaller than from the Karmoy area. Specimens from the Koster area were up to about 15 cm maximum diameter, but most were smaller than 12 cm. Large quantities of G. atlantica, S. ponderosus and T. valdiviae were collected at Karmoy together with a few specimens of G. macandrewi (Table 4). Both the two species of Geodia and the Thenea species were missing from the Koster area. A tendency towards a gradient in the distribution of the species is seen along the Trondheim Fjord, G. atlantica and I. phlegraei being present in the seaward basin, while only a few fragments of both species were sampled in the middle and inner basins. Only one fragment of G. macandrewi was sampled in the Trondheim Fjord, in Skarnsundet between the middle and the inner basin. Few fragments or specimens of S. ponderosus and T. levis and one specimen of T. valdiviae were collected in the seaward basin, and none of these species were found in the middle and inner basins (Table 5). On the other hand, several specimens of T. muricata were sampled living on the muddy bottom of the Trondheim Fjord, this species generally being found in fjords, although not in the Koster area. S. normani seems to be a ‘‘here and there’’ species, with only a few specimens having been sampled in the Koster area and in the three basins of the Trondheim Fjord (Table 5). Thus, a comparison of the composition and distribution of astrophorid species in the Trondheim Fjord and the Koster area with the outer coast (the Karmoy area) shows that in the fjords the specimens are often smaller, and some species are absent. 5.2.3. Ridge areas The sponge accumulations known around Iceland have primarily been found in areas of complicated topography where there are hard bottoms. Thus, the BIOICE ‘‘ostur’’ stations are on the slope of a small

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

89

bank northeast of Iceland, on a seamount which is part of the Kolbeinsey Ridge in an area where muddy astrophorid spicule mats are found locally, on the slope of the northern and southern part of the Denmark Strait Channel and on the Reykjanes Ridge. Catches of sponges of over 20 tons have been reported by Icelandic fishery biologists from the top and upper slope of the Reykjanes Ridge, where the bottom topography is varied with areas of both hard and soft substrata. Considering the intensity of the sampling, remarkably few areas with ‘‘ostur’’ were located during the BIOICE programme; only seven of the approximate 600 samples taken with dredges, sledges and Agassiz trawl from 1991 to 1995 were in such areas; all were at depths >300 m, and the majority >600 m (Table 1). Although, almost 400 of the BIOICE samples were from >300 m and 213 were from >600 m depth. The surficial sediments around Iceland are very variable and part of an explanation for the low frequency of ‘‘ostur’’ areas may be that extensive areas off the north and south coast are covered with silty or muddy sediments of volcanic origin that do not constitute suitable substrata for the settlement and establishment of astrophorid sponges. An additional factor may be that the discharges of melt waters from the glaciers along the south coast of Iceland carry large amounts of suspended inorganic particles which not only increase the turbidity of the shelf water but also probably prevent or diminish the establishment of suspension feeding benthic organisms such as sponges by clogging their filtration systems. Only very few sponges have been sampled from the southern plateau. During the BIOFAR and BIOICE cruises three transects were sampled across the Iceland-Faroe Ridge, and another was carried out by the Danish Ingolf Expedition in 1896. However, not a single area with ‘‘ostur’’ was found despite most of the bottom being gravelly, sometimes with boulders. Increased turbidity or lack of a hard substratum can clearly not be the factor in this case. Another suggestion is that the polar front, which separates the cold Arctic Intermediate water from the warmer Atlantic water and typically slopes from the crest of the Iceland-Faroe Ridge towards the northeast, is known to meander back and forth across the ridge giving rise to an intermittent overflow of cold water (Hansen & Meincke, 1979; Hansen & Østerhus, 2000). The instability of the water masses causes large variations of the bottom temperature and relatively low temperatures on the southern slope of the Iceland-Faroe Ridge (Westerberg, 1991), and this might prevent the local establishment of either the boreal or the cold water ‘‘ostur’’ assemblages (see below). 5.3. Taxonomic composition and hydrographic regime A number of species which occur both in the Norwegian and Greenland Seas have been described as having both a coldwater and a warmwater ‘‘form’’. The differences between these morphological types are small and variable, and have been interpreted differently by a number of authors, who have characterized them as being either species, subspecies or ‘‘forms’’. Our extensive material shows that the distributions of these types distinguished by quite small differences seem to coincide with differences in environmental conditions (especially hydrography). Rather than ignore these relatively minor taxonomical and biological characteristics, we have preferred, in a number of cases, to consider them, for the time being, to be of specific importance. This enables us to recognize two main types of ‘‘ostur’’ assemblages in the Northeast Atlantic (Table 6). ‘‘Ostur’’ from the the Faroe Islands, Norway, Sweden, parts of the western Barents Sea and south of Iceland have almost the same complement of dominant species, mainly boreal in their distributions and rarely occurring at temperatures lower than about 3 C (G. barretti, G. macandrewi, G. atlantica, I. phlegraei, S. ponderosus and S. normani). In the colder waters north of Spitzbergen, north of Iceland, in most of the Denmark Strait and off East Greenland the dominant genera are the same, but the species are mostly different, (G. mesotriaena, I.p. pyriformis and S. rhaphidiophora). Besides the demosponges, species of hexactinellids occur in the colder water; the most common species is Scandinnia rosea, but Schyphidium septentrionale, Trichasterina borealis and Asconema setubalense are regularly seen.

90

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

A clear difference between the boreal and the cold water ‘‘ostur’’ is in the average size of the dominant geodiid species. Comparing Fig. 4 with Figs. 7 and 8 clearly demonstrates the much larger average size of the warmer water species G. barretti relative to G. mesotriaena and I.p. pyriformis. Although too few undamaged specimens of the boreal I. phlegraei were collected to construct size-frequency diagrams, specimens sampled at Karmoy were up to 39 cm in maximum diameter, and at the Faroe Islands were up to 43 cm in diameter compared to the largest specimen of I.p. pyriformis sampled in the Denmark Strait being 26 cm, and most specimens there were <15 cm (Fig. 7). Even though G. macandrewi has a firmer consistency, too few specimens were collected to construct size-frequency diagrams. However, it too shows the same trend in size as seen in G. barretti and I. phlegraei. The two specimens sampled at Karmoy measured 17 and 29 cm in maximum diameter. Similarly, the three specimens sampled at Iceland measured 12, 13 and 19 cm in diameter respectively. Most specimens have been collected from the Faroe Islands and in the Denmark Strait. The majority of the specimens at the Faroe Islands measured between 10 and 35 cm in diameter, the smallest and largest specimen being 3 and 37 cm, respectively, in maximum diameter; however, only few specimens smaller than 10 cm were collected. The smallest specimens in the Denmark Strait measured 3 cm while the largest specimen was 42 cm in diameter, most specimens measuring between 10 and 30 cm in diameter. Because the dominant boreal G. atlantica suffers the same problem of extensive fragmentation during sampling as I. phlegraei it was not possible to elaborate size-freqency diagrams. The samples do, however, indicate that it is of an average size larger than the cold water geodiid species. No specimens or fragments of G. atlantica smaller than 13 cm were sampled at Karmoy, the majority being larger than 20 cm in maximum diameter, and similarly only few specimens or fragments smaller than 10 cm were collected at the Faroe Islands, the majority being larger than 20 cm, the largest whole specimen measuring 72 cm in diameter. 5.4. Other parts of the world The occurrence of mass accumulations of large sponges in sublittoral and upper bathyal depths is a widespread phenomenon. It was mentioned above that the northern coldwater association is found at 1000 m depth north of Spitzbergen (Hentschel, 1929; Schulze, 1900); and Koltun (1959a, 1959b, 1966, 1967, 1970) possibly showed that it also occurs north of Franz Josef Land. Isops cf. phlegraei from the west of Ellesmere Land has been reported covering extensive areas at depths of 100–150 m where it lives on pebbles and tetractinellid spicule mats up to 10 cm thick (Wagoner, van Mudie, Cole, & Daborn, 1989). Bottom photographs from the area indicate the presence of a very rich animal life in general, with sponges up to about 30 cm diameter standing so close together that they are in contact with each other, sometimes even growing on top of their neighbours. Thus, ‘‘ostur’’ may be widely distributed over large parts of the Polar Sea, especially on the eastern shelf and slope areas. Large numbers of geodiid sponges have been reported from the NE Pacific sublittoral off Alaska (Kozloff, 1987). Mass occurrences of hexactinellids have been documented off western Canada, at depths of 150–250 m, consisting of the three species Aphrocallistes vastus Schulze, 1886; Heterochone calyx (Schulze, 1886) and Farrea occa Bowerbank, 1862 (Conway, Barrie, Austin, & Luternauer, 1991; Krautter, Conway, Barrie, & Neuweiler, 2001). The sponges live on a substrate of a thick layer of dead sponge skeletons. In the North Atlantic off Morocco and the west of Ireland and Scotland large masses of the hexactinellid Pheronema carpenteri (Thomson, 1869) have been reported from 740 to 1300 m depth (Barthel, Tendal, & Thiel, 1996; Carpenter, Jeffreys, & Thomson, 1870; Rice, Thurston, & New, 1990). There are indications that this species may also be common to the west of the Faroe Islands and south of Iceland, at depths from between 800 and 1160 m (Burton, 1928; Copley, Tyler, Sheader, Murton, & German, 1996; own observations from several BIOICE stations). Bett (2001) reports the presence of ‘‘ostebund’’ formed by aggrega-

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

91

tions of large demosponges in the Faroe-Shetland Channel at depths of around 500 m. Bett (2001) describes these occurrences as ‘‘some of these growths practically carpet the seafloor, and while they are principally composed of rather small specimes, large sponges (tens of centimetres in diameter) are nevertheless common’’. The largest accumulations of sponges known occur on the Antarctic shelf (Barthel & Tendal, 1994; Dayton, Robilliard, Paine, & Dayton, 1974; Koltun, 1970 and citations therein). In strong contrast to the sponge accumulations of the northern hemisphere sublittoral, they are composed predominately of large hexactinellids of the family Rossellidae, together with a sparse scattering of species of the demosponge families Geodiidae, Ancorinidae and Theneidae which never dominate. 5.5. Changes in distribution of ‘‘ostur’’ over time The large size, low organic content (compared to the amount of silicious skeleton), and predominance of large specimens in the catches from ‘‘ostur’’ communities lead us to the assumption that the dominant species are slow growing and probably take at least several decades to reach the sizes commonly encountered. They seem always to be found in relatively constant environmental conditions, which suggests that they are dependent on a certain stability with respect to water mass characteristics, kinds and amount of particles in the water, and on low physical disturbance. The experience of fishery biologists and fishermen is that although ‘‘ostur’’ is found in the same general area over long periods of time, the localities where there are the highest concentrations may change; in fact, some fishermen say ‘‘the ostur is wandering’’. A similar phenomenon was reported by Barthel et al. (1996) for the hexactinellid P. carpenteri on the basis of a photographic investigation. Blacker (1957, 1965) having mapped changes in the distribution of selected large invertebrates off Bear Island and West Spitzbergen concluded that since 1920 Atlantic species, among them G. barretti, had spread northwards; the large accumulations of G. barretti would hardly have been overlooked had they been there before that time. He ascribed the changes to the influence of a stronger inflow of Atlantic water to the area. Dyer et al. (1984) were uncertain about BlackerÕs conclusions, finding more arctic species in 1978–1981 than he did, but corroborated his results concerning G. barretti. Erekovsky (1995) comparing quantitative data of sponges sampled in the western Barents Sea in 1920–1950 and 1960–1980 found that during this period total sponge biomass had decreased 6.6-fold, mainly due to reductions of the boreal-arctic species. During the same time the sponge biomass component of the total benthic biomass in these areas practically did not change. Unfortunately he gave no information as to which sponge species may have regressed or become smaller. One cause of such changes over time, could be a slow shifting in the position of the polarfront; it is rather narrow and moves only a little way off Spitzbergen and Bear Island, while it is broader and less well defined between Bear Island and northern Norway (Loeng, Mork, & Slagstad, 1992). Physical damage can result from various causes. In the Denmark Strait, ice-berg scour marks are common on the banks and the channel-floors down to depths of about 350 m (Larsen, 1983). The marks are so deep and numerous that in some areas the upper 5–10 m layer of the sediment has been ploughed up. Such events represent local catastrophies, where the total benthic community has been killed either by being crushed or by being buried. Some localities where very large numbers of mainly small sponges were found, may represent such places which have recently been recolonized (Fig. 7, St. nos. 94PA0090043 and 94PA0090062). Even so the destructive events may have happened a long time previously because of the presumed very slow growth of the sponges. Gutt and Koltun (1995) briefly touched upon the possible influence of iceberg scouring on the structure of certain Antarctic sponge assemblages. A special kind of physical disturbance occurs when water near the bottom becomes more heavily loaded with suspended material that sediments out, covering the surface of the sponge and clogging its filtration system. Intense resuspension can be caused by sediment slides, violent storms, unusually high internal waves and, in modern times, by nearby trawling.

92

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

A limited degree of sedimentation on the surface does not seem to be damaging, as bottom photographs often show healthy-looking astrophorid sponges with a fine covering of particles. Clogging of their channel system by small particles is, on the other hand, more serious, as all particles no matter what their nutritional value is have to be transported through the sponge by wandering cells to be discharged into the excurrent system. For large, lumpy sponges the transportation may be long, imposing a relatively high energy demand. In G. atlantica, we have observed a possible mechanism whereby the problem of intermittent clogging of the system may be solved. This species as it ages develops a gross morphology in the form of thick plates on which the inhalent system is on one side, and the exhalent on the other. In some specimens, when the plate is cut through, the inhalent system is seen to be grey-coloured from large amounts of fine particles, seemingly being stored until further transport is possible, while the exhalent system is clean. We hypothesise that after a resuspension event the sponge becomes overfilled, but is still able to maintain sufficient current for metabolism, although it can only handle the large amounts of particles slowly. If this happens too often, the sponge may no longer be able to clean itself and its metabolic activity may be depressed to a level at which the species can no longer survive. The adverse effects of heavy sedimentation on sponges and other animals have been examined by Bakus (1968), although in a completely different enviroment. Intensive trawling probably leads rapidly to severe depletion of ‘‘ostur’’ areas. During our investigations around the Faroes, we sampled areas indicated as ‘‘ostur’’ in the book ‘‘To´v’’ (Anonymous, 1988) at which we found no sponges; fishermen told us that trawling had recently begun in these areas. Severe damage probably occurs as the trawl is dragged along the bottom, but a large part of the catch may also be killed. Sponges tipped out on deck, even if undamaged, will be drained of water and are unlikely to recover when thrown back into the sea. If the trawl is completely filled the catch may not be brought on deck, but emptied directly back into the sea. Sponges sinking en masse back onto the bottom may end upside down or on the wrong type of bottom. On the other hand, it is possible that new areas may be colonized by dispersal resulting from trawling. There have been no investigations of the effects of trawling on ‘‘ostur’’, but there is some experience of trawling on other sponge faunas. Dolah, Wendt, and Nicholson (1987) found that at 20 m depth off Georgia one experimental trawling with a relatively small trawl caused varying degrees of damage to the sponges and octocorals, but after 12 months the fauna had completely recovered. Since most of these species were fast growing, rapid repair of any damage is to be expected. However, this is unlikely to happen after a trawl has dragged through ‘‘ostur’’ areas in our waters. We have rarely found signs of repair and the dominating sponges have a very strict organisation that can hardly function after physical damage of the cortex. Hoffmann, Rapp, Zo¨ller, and Reitner (2003) reported slow regeneration in cultivated fragments of G. barretti under circumstances that hardly apply to natural conditions. Sainsbury (1988) reported that trawling on the north-west shelf of Australia resulted in a significant loss of sponges and octocorals after about 10 years, and this led to changes in the composition of the fish fauna. Modern trawlers are working deeper than before, extending the fishing grounds, and so are destroying areas of ‘‘ostur’’ and coralbanks. Fishermen of various nationalities have told us that certain bottom areas are being ‘‘improved’’ by repeatedly towing just the large bobbin gear over the bottom, crushing the sponges and corals that would otherwise fill up the trawl; so that gradually the area is ‘‘improved’’ into a reasonable trawling ground. An important aspect when considering changes in the distribution of ‘‘ostur’’ is how and when the species reproduce. Geodiidae and Ancorinidae belong to the Tetractinomorpha in which the reproductive pattern is typically oviparous. The eggs are extruded and the development is external and is either direct or by way of a larval stage (Bergquist, 1978; Hooper & Van Soest, 2002). Except for a few descriptions of the early stages in Mediterranean species (Liaci & Sciscioli, 1967, 1969), no investigations of the sexual reproduction in geodiids and ancorinids have been carried out, and the larvae have not been described for these families. Specimens of G. mesotriaena and I.p. pyriformis with spherical stalked buds distributed mainly on the upper half of the bodies occurred regularly in the samples from the Denmark Strait, and numerous very

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

93

small, young geodiids (maximum diameter <1 cm) were sampled at some of these stations (these specimens were not included in Figs. 7 and 8). Bud formation in geodiids of unspecified arctic origin was reported by Burton (1947/1948) in what he hesitantly referred to as G. barretti. We have found no sign of any buds whatsoever in the boreal geodiids, and are of the opinion that BurtonÕs samples were of either G. mesotriaena or I.p. pyriformis buds. The lack of small specimens in the areas investigated is remarkable (Fig. 4). Reproduction in the boreal ‘‘ostur’’ areas must be an infrequent event, which makes ‘‘ostur’’ vulnerable both to changes in the local hydrographic regime, and to direct as well as indirect impacts of trawling. 5.6. Biological importance of ‘‘ostur’’ In situ investigations are needed in order to outline in more detail the biological role of ‘‘ostur’’. Nevertheless on the basis of our experience gathered from examining many ‘‘ostur’’ catches, series of underwater photographs of ‘‘ostur’’ taken during a BIOFAR cruise in May 1990 at the Faroe Islands among other areas (Fig. 9) (J. Gutt, Alfred-Wegener, Institut fu¨r Polar- und Meeresforshung, Bremerhaven) we make some suggestions. Firstly the presence of large-sized astrophorid sponges increases the physical heterogeneity of the local area and the number of available microhabitats. Fauna associated with the dominant sponges in ‘‘ostur’’ areas at the Faroe Islands (including G. barretti, G. macandrewi. G. atlantica, I. phlegraei and S. ponderosus) is rich (>242) in species (Klitgaard, 1991, 1995; Ware´n & Klitgaard, 1991). Sponge morphology influences the composition of the associated fauna; presence of a spicule ‘‘fur’’, cavities like the oscular cavity of S. ponderosus, and the incurrent furrows of T. levis and T. valdiviae are microhabitats exploited by nematodes, polychaetes, isopods, sipunculids and ophiuroids. The associated fauna is, however, dominated by epifaunal groups such as encrusting sponges, hydroids, zoantharians, bryozoans and ascidians that use the sponges as a substratum. In turn the epifauna provide substrata for further epibionts (Monniot & Klitgaard, 1994; pers. obs.). The majority of the associated species are facultative being found as members of the local fauna outside ‘‘ostur’’ zones; this seems to be a general phenomenon in temperate/ cold waters for sponges (Klitgaard, 1995) as well as for Lophelia pertusa (Jensen & Frederiksen, 1992). A rich and diversified fauna has also been demonstrated to be facultatively associated with hexactinellid accumulations in the Weddell Sea, Antarctica (Kunzmann, 1996). Another feature of ‘‘ostur’’ is that when the sponges die, large amounts of spicules are released. These can either form a local spicule mat on the bottom, or be transported by bottom currents to other localities. A number of localities with spicule mats were found around the Faroe Islands and Iceland and off East Greenland. The bathyal hexactinellid P. carpenteri, which also forms dense populations in the Porcupine Seabight (NE Atlantic) (Bett & Rice, 1992; Rice et al., 1990) and off Morocco (NW Africa) (Barthel et al., 1996) produces thick mats of spicules locally. This phenomenon has also been reported from regions of seabed dominated by hexactinellids around Antarctica (Barthel, 1992; Barthel & Tendal, 1994). The occurrence of large quantities of hexactinellid spicules changes both the composition and structure of the local sediment and the composition of the local benthic fauna. Thus, Bett and Rice (1992) reported a considerable increase in the numerical abundance of macrobenthos in core samples containing spicule mats relative to samples without them. Astrophorid sponges have not yet been observed to generate spicule mats as extensive as hexactinellids. Nevertheless, several litres of tetractinellid spicules were collected at some stations in the Denmark Strait, and considering that some spicules are undoubtedly washed out of trawls during recovery, they probably constitute an important component of the substratum in these areas. In addition the tetractinellid spicule mats often consist of balls of compressed spicules almost as though the single geodid sponges having died, collapsed on the spot, something also reported for P. carpenteri (Barthel et al., 1996). Fishermen have informed us that commercial species of fish regularly caught in ‘‘ostur’’ regions in the Barents Sea include Reinhardtius hippoglossoides (Walb.), Melanogrammus aeglefinus (L.) and Gadus morhua (L.), and off East Greenland include Sebastes sp. and Reinhardtius hippoglossoides. Furthermore, we observed large numbers of redfish (Sebastes sp.) in trawls from ‘‘ostur’’ areas around the Faroe Islands

94

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

during the BIOFAR programme. The heterogenous nature of the ‘‘ostur’’ areas and the presence of a rich mixed fauna of invertebrates, probably makes them well suited as recruitment areas for certain species of fish. It would seem logical to direct future research towards the potential for designating ‘‘ostur’’ regions as refuges from which the dispersal of invertebrates as well as fishes could replenish the surrounding trawled areas, such as has been proposed already for other types of marine habitats (Dugan & Davis, 1993). 6. Conclusions (1) Scattered information compiled from fishermen, fishery biologists from a number of countries, and the scientific literature, as well as our own investigations show occurrences of mass concentrations of large sponges to be widespread throughout the Northeast Atlantic. Such areas are called ‘‘ostur’’, meaning cheese, by fishermen in the Faroes, from where the first detailed description of the phenomenon was made in the North Atlantic, and a first rough definition was formulated (Klitgaard et al., 1997). (2) ‘‘Ostur’’ regions in the Faroes are dominated by species of the astrophorid families Geodiidae and Ancorinidae, and this has been found to be the case in the Arctic and all over the Northeast Atlantic (north of 60N) influenced by the North Atlantic Drift and its main branches. The warm water (‘‘Atlantic’’) association is found at the Faroes, along the Norwegian and Swedish coasts, in the southwestern Barents Sea, and along the continental edge of the western Barents Sea to the west of Spitzbergen, south of Iceland and in the southeastern Denmark Strait. (3) Where ‘‘ostur’’ occurs in the fjords of Norway and fjord-like localities in the Skagerak the same genera dominate, but the number of species decreases. (4) The same genera dominate ‘‘ostur’’ regions in coldwater Arctic areas but are represented by different species. The cold water (‘‘Arctic’’) association is distributed in the main part of the Denmark Strait, north of Iceland, along East Greenland into the Polar Sea, where it is found north of Spitzbergen and there are indications that it exists also north of Franz Josef Land and off Ellesmere Island. (5) ‘‘Ostur’’ regions have been found on the edge of the shelf plateau, on the sides of banks, near the shelf edge and on the upper slope. They occur most frequently where the topography is highly irregular so special hydrographic conditions can be expected, such as the breaking of internal waves and acceleration of local currents. (6) Accumulations of large sponges, but of different taxonomic composition are found in other parts of the Atlantic, and in the North Pacific and Antarctic oceans. (7) The species dominating ‘‘ostur’’ regions seem to reproduce slowly and be slow growing. The areas would seem to be stable, but also to demand constant local conditions in order to develop. Changes, slow or catastrophic, are likely to be caused by changes in water mass distribution and by physical damage, such as scouring by icebergs, trawling and strong and frequent resuspension. (8) Through their presence ‘‘ostur’’ assemblages increase the physical heterogeneity of the bottom, and over time they change the local sediment structure through the release of spicules at their death, sometimes in such large amounts that areas of the bottom are covered with a muddy spicule mat. Other investigations of these ‘‘ostur’’ areas have shown the associated fauna to be rich and varied. If left undisturbed from fishing activity, they might serve as refuges from which there could be replenishment of nearby trawling grounds with both fish species and their prey. Acknowledgements The Steering Committees for the BIOFAR and BIOICE programmes are thanked for giving the authors the opportunity to participate in all BIOFAR cruises during 1987–1990 and in the majority of the BIOICE cruises during 1991–96. Dr. Jon-Arne Sneli (University of Trondheim) is thanked for very rewarding stays

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

95

for ABK at Trondhjem Biologiske Stasjon in 1989 and 1994. The late Dr. Lars Afzelius (Tja¨rno¨ Marinbiological Laboratory) was very generous in letting OST use shiptime and other facilities during numerous visits. We thank Drs. Per Kanneworff and Klaus Lehmann (the Greenland Institute for Natural Resources, Nuuk, Greenland), Dr. Stein Tveite (Havforskningsinstituttet, Forskningsstasjonen Flødevigen, His, Norway), Dr. Svend Lemvig (University of Bergen, Department of Fisheries and Marine Biology, Norway), chief officer Jon Simonsen of R/V Paamiut (Sandava´g, the Faroe Islands), Dr. Sigmar A. Steingrimsson (Hafrannso´knastofnun, Marine Research Institute, Reykjavik, Iceland), and Dr. Chr. Karrer (Bundesforschungsanstalt fu¨r Fischerei, Institut fu¨r Seefischerei, Hamburg, Germany) for supplying information regarding ‘‘ostur’’. The crews of the Faroese R/V Magnus Heinason (Fiskirannso´knarstovan, To´rshavn), the Faroese coastguard vessel Tjaldrid, the Norwegian R/V Ha˚kon Mosby (University of Bergen), the Norwegian R/V Harry Borthern (University of Trondheim, Trondhjem biologiske stasjon), the Swedish R/V Virgo (University of Go¨teborg, Tja¨rno¨ Marine Biological Laboratory), the Icelandic R/V Bjarni Sæmundsson (Hafrannso´knastofnun, Reykjavik), the Greenlandic R/V Paamiut (the Greenland Institute for Natural Resources, Nuuk) are acknowledged for their excellent help onboard. Dr. Per Kanneworff, Ms. Solveig S. Buhl and Mr. Casper Christoffersen are especially thanked for their kind help and very pleasant company onboard R/V Paamiut. Dr. Birger Larsen (Geological Survey of Denmark and Greenland, Copenhagen) is greatly acknowledged for permitting the use of the topographical chart of the Denmark Strait, published in Larsen (1983). Dr. Dagmar Barthel (Brussels) is thanked for allowing us to use unpublished results of the sponge species composition at stations taken during R/V Polarstern cruise ARK X/1 in 1994 at NE Greenland. Drs. Ha˚kan Westerberg (National Board of Fisheries, Institute of Coastal Research, Va¨stra Fro¨lunda, Sweden) and Arne Johannessen (University of Bergen, Department of Fisheries and Marine Biology) are thanked for various information. We thank Dr. Julian Gutt (Alfred-Wegener-Institut fu¨r Polar- und Meeresforshung, Bremerhaven) for providing underwater photos during the BIOFAR programme. Miss Shirley M. Stone (The Natural History Museum, London) kindly commented on the manuscript and revised the English. The investigation was supported by the Danish Natural Science Research Council (ref. no. 11-0571-1 PD/jl) (ABK), the BIOFAR and BIOICE programmes (ABK and OST), Professor Johannes Smith, D.Sc.Õs Trust for Marine Science (ABK) and Zoological Travel- and Excursionfund, Danish Society of Natural History (ABK).

References Alander, H. (1942). Sponges from the Swedish west-coast and adjacent waters. Go¨teborg, 95 pp. Anonymous (1988). To´v. Magnus Heinason, Fiskirannso´knarstovan, Pf. Einars prent: Torshavn, 67 charts. Appelo¨f, A. (1912). Invertebrate bottom fauna of the Norwegian Sea and North Atlantic. In J. Murray & J. Hjort (Eds.), The depths of the ocean (pp. 457–560). London. Arndt, W. (1913). Zoologische Ergebnisse der ersten Lehr-Expedition der Dr. P. Scottla¨nderschen Jubila¨ums-Stiftung. I. Coelenterata, Bryozoa, Brachiopoda und Pycnogonidea. Jahresbericht der Schlesischen Gesellschaft fu¨r vaterla¨ndische Kultur, 90, 110–119. Bakus, G. (1968). Sedimentation and benthic invertebrates of Fanning Island, Central Pacific. Marine Geology, 6, 45–51. Barthel, D. (1992). Do hexactinellids structure antarctic sponge associations?. Ophelia, 36, 111–118. Barthel, D., & Tendal, O. S. (1994). Antarctic Hexactinellida. Synopses of the Antarctic Benthos, 6, 1–154. Barthel, D., Tendal, O. S., & Thiel, H. (1996). A wandering population of the hexactinellid sponge Pheronema carpenteri on the continental slope off Morocco, Northwest Africa. Marine Ecology, 17, 603–616. Bergquist, P. R. (1978). Sponges. London: Hutchinson and Co Ltd 268 pp. Bett, B. J. (2001). UK Atlantic margin environmental survey: Introduction and overview of bathyal benthic ecology. Continental Shelf Research, 21, 917–956. Bett, B. J., & Rice, A. L. (1992). The influence of the hexactinellid sponge (Pheronema carpenteri) spicules on the patchy distribution of macrobenthos in the Porcupine Seabight (bathyal NE Atlantic). Ophelia, 36, 217–226. Blacker, R. W. (1957). Benthic animals as indicators of hydrographic conditions and climatic change in Svalbard waters. Fishery Investigations (London), Series II, 20, 1–49.

96

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Blacker, R. W. (1965). Recent changes in the benthos of the west Spitzbergen fishing grounds. International Commission for the Northwest Atlantic Fisheries special Publication, 6, 791–794. Blindheim, J., Buch, E., Fogelqvist, E., Tanhua, T., & Østerhus, S. (1996). The R/V Johan Hjort 1994 NORDIC WOCE cruise: On hydrography and tracers. ICES C.M. 1996/O, 20, 1-15 + eleven figures. Bruntse, G., & Tendal, O. S. (2001). Summary. In G. Bruntse & O. S. Tendal (Eds.), Marine biological investigations and assemblages of benthic invertebrates from the Faroe Islands (80 pp). Kaldbak Marine Biological Laboratory. Brøndsted, H. V. (1932). Marine Spongiae. In Ad. S. Jensen, W. Lundbeck, Th. Mortensen, & R. Spa¨rck (Eds.). The zoology of the Faroes 1 (1, pp. 1–34). Copenhagen: Andr.Fred.Høst & Son 1928–1942. Buch, E. (1991). A monograph on the physical oceanography of the Greenland waters. Copenhagen: Royal Danish Administration of Navigation and Hydrography 405 pp. Burton, M. (1928). Hexactinellida. The danish Ingolf-Expedition, 6(4), 1–18. Burton, M. (1930). Norwegian sponges from the Norman collection. Proceedings of the Zoological Society of London, Part 2, 487– 546 + 2 plates. Burton, M. (1934). Report on the sponges of the Norwegian expeditions to East Greenland. Skrifter om Svalbard og Ishavet, 61, 1–33. Burton, M. (1947/1948). Non-sexual reproduction in sponges, with special reference to a collection of young Geodia. Proceedings of the Linnean Society of London, 160, 163–178. Carpenter, W. B., Jeffreys, J. G., & Thomson, C. W. (1870). Preliminary report on the scientific exploration of the deep sea in H.M. surveying vessel ‘‘Porcupine’’ during the summer of 1869. Proceedings of the Royal Society of London, 18, 397–492. Conway, K. W., Barrie, J. V., Austin, W. C., & Luternauer, J. L. (1991). Holocene sponge bioherms on the western Canadian continental shelf. Continental Shelf Research, 11, 771–790. Copley, J. T. P., Tyler, P. A., Sheader, M., Murton, B. J., & German, C. R. (1996). Megafauna from sublittoral to abyssal depths along the Mid-Atlantic Ridge south of Iceland. Oceanologica Acta, 19, 549–559. Dayton, P. K., Robilliard, G. A., Paine, R. T., & Dayton, L. B. (1974). Biological accomodation in the benthic community at McMurdo Sound, Antarctica. Ecological Monographs, 44, 105–128. Dolah, R. F. V., Wendt, P. H., & Nicholson, N. (1987). Effects of a research trawl on a hardbottom assemblage of sponges and corals. Fisheries Research, 5, 39–54. Dugan, E. J., & Davis, G. E. (1993). Applications of marine refugia to coastal fisheries management. Canadian Journal of Fisheries and Aquatic Sciences, 50, 2029–2042. Dyer, M. F., Cranmer, G. J., Fry, P. D., & Fry, W. G. (1984). The distribution of benthic hydrographic indicator species in Svalbard waters, 1878–1981. Journal of the Marine Biological Association of the United Kingdom, 64, 667–677. Erekovsky, A. V. (1993). Materials for the faunistic study of the White Sea and Barents Sea sponges I. Taxonomic composition. Bulletin of St. Petersborg University, 3, 19–28 (In Russian). Erekovsky, A. V. (1995). Materials to the faunistic study of the White and Barents seas sponges. 5. Quantitative distribution. Berliner Geowissenschaftliche Abhandlungen E, 16, 709–714. Filatova, Z. A. (1938). The quantitative evaluation of the bottom fauna of the south-western part of the Barents Sea. Transactions of the Knipovich Polar Scientific Institute of Sea-Fisheries and Oceanography, 2, 3–58. Fleischer, U., Holzkamm, F., Vollbrecht, K., & Voppel, D. (1974). Die Struktur des Islands-Fa¨ro¨er-Ru¨ckens aus geophysikalischen Messungen. Deutsche Hydrographische Zeitscrift, 27, 97–113. Frederiksen, R., Jensen, A., & Westerberg, H. (1992). The distribution of the scleractinian coral Lophelia pertusa around the Faroe Islands and the relation to internal tidal mixing. Sarsia, 77, 157–171. Gutt, J., & Koltun, V. M. (1995). Sponges of the Lazarev and Weddell Sea, Antarctica: explanations for their patchy occurrence. Antarctic Science, 7, 227–234. Hansen, B. (1985). The circulation of the northern part of the Northeast Atlantic. Rit Fiskideildar, 9, 110–126. Hansen, B., & Meincke, J. (1979). Eddies and meanders in the Iceland-Faroe Ridge area. Deep-Sea Research, 26A, 1067–1082. Hansen, B., & Østerhus, S (2000). North Atlantic – Nordic Seas exchanges. Progress in Oceanography, 45, 109–208. Hansson, H. G. (1976). Kosterra¨nnan och de grundare havsomra˚dena inom Stro¨mstads kommun. La¨nsstyrelsen i Go¨teborgs och Bohus La¨n: Go¨teborg, 51 pp. Henrich, R., Hartmann, M., Reitner, J., Scha¨fer, P., Freiwald, A., Steinmets, S., et al. (1992). Facies belts and communities of the Arctic Vesterisbanken Seamount (Central Greenland Sea). Facies, 27, 71–104. Hentschel, E. (1929). Die Kiesel- und Hornschwa¨mme des No¨rdlichen Meeres. Fauna Arctica, 5, 859–1042. Hoffmann, F., Rapp, H. T., Zo¨ller, T., & Reitner, J. (2003). Growth and regeneration in cultivated fragments of the boreal deep water sponge Geodia barretti Bowerbank, 1858 (Geodiidae, Tetractinellida, Demospongiae). Journal of Biotechnology, 100, 109–118. Hooper, J. N. A., & Van Soest, R. W. M. (Eds.). (2002). Systema Porifera. A guide to the classification of sponges (1708 pp in two volumes). New York: Kluwer Academic/Plenum Publishers. Jacobson, P. (1983). Physical oceanography of the Trondheimsfjord. Geophysics and Astrophysics. Fluid Dynamics, 26, 3–26. Jensen, A., & Frederiksen, R. (1992). The fauna associated with the bank-forming deepwater coral Lophelia pertusa (Scleractinaria) on the Faroe shelf. Sarsia, 77, 53–69.

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

97

Ja¨gerskio¨ld, L. A. (1971). A survey of the marine benthonic macro-fauna along the Swedish west coast 1921–1938. In B. Hubendick, G. Hyle, & S. Swa¨rd (Eds.), Acta Regiae Societatis Scientarum et Litterarum Gothoburgensis. Zoologica (vol. 6, pp. 1–145). Klitgaard, A. B. (1991). Gnathia abyssorum (G.O. Sars, 1872) (Crustacea, Isopoda) associated with sponges. Sarsia, 76, 33–39. Klitgaard, A. B. (1992). The fauna associated with sponges (Porifera) at the Faroe Islands. MSc Thesis, Zoological Museum, University of Copenhagen, Denmark (306 pp), unpublished. Klitgaard, A. B. (1995). The fauna associated with outer shelf and upper slope sponges (Porifera, Demospongiae) at the Faroe Islands, northeastern Atlantic. Sarsia, 80, 1–22. Klitgaard, A. B., Tendal, O. S., & Westerberg, H. (1997). Mass occurrences of large-sized sponges (Porifera) in Faroe Island (NEAtlantic) shelf and slope areas: characteristics, distribution and possible causes. In L. E. Hawkins, & S. Hutchinson, with A. C. Jensen, M. Sheader, & J. A. Williams (Eds.), The responses of marine organisms to their environments (pp. 129–142). University of Southampton: Proceedings of the 30th European Marine Biology Symposium. Koltun, V. M. (1959a). Fauna from the abyssal of the central Polar Basin. Doklady, 129, 662–665 (in Russian). Koltun, V. M. (1959b). Cornacousilicious sponges of the northern and far eastern seas of the USSR. Keys to the fauna of the USSR. Academy of Sciences of USSR, 67, 1–235 (in Russian). Koltun, V. M. (1964). Porifera. In Z.S. Gorjunova & V.S. Suvalov (Eds.), Scientific results in the higher latitudes. Oceanographic investigations in the northern part of the Greenland Sea and the adjacent Arctic Basin. Works from the Arctic and Antarctic Scientific Institute (Vol. 259, pp. 143–166, in Russian). Koltun, V. M. (1966). Tetraxonida of the northern and far eastern seas of the USSR. Keys to the fauna of the USSR. Academy of Sciences of USSR, 90, 1–107 (in Russian). Koltun, V. M. (1967). Hexactinellid sponges of the northern and far eastern seas of the USSR. Keys to the fauna of the USSR. Academy of Sciences of USSR, 94, 1–124 (in Russian). Koltun, V. M. (1970). Sponges of the Arctic and Antarctic; a faunistic review. Symposia of the Zoological Society of London, 25, 285–297. Kozloff, E. N. (1987). Marine invertebrates of the Pacific Northwest. Seattle, WA: University of Washington Press 285–297, Not seen. Krautter, M., Conway, K. W., Barrie, J. V., & Neuweiler, M. (2001). Discovery of a ‘‘living Dinosaur’’: Globally unique modern Hexactinellid sponge reefs off British Columbia, Canada. Facies, 44, 265–282. Kunzmann, K. (1996). Die mit ausgewa¨hlten Schwa¨mmen (Hexactinellida und Demospongiae) aus dem Weddellmeer, Antartkis, vergesellschaftete Fauna. Berichte zur Polarforschung, 210, 1–93. Larsen, B. (1983). Geology of the Greenland-Iceland Ridge in the Denmark Strait. In M. H. P. Bott, S. Saxov, M. Talvani, & J. Thiede (Eds.), Structure and development of the Greenland-Scotland Ridge (pp. 425–444). Plenum Press. Liaci, L., & Sciscioli, M. (1967). Osservazioni sulla maturazione sessuale di un tetractinellida: Stelletta grubii O.S. (Porifera). Archivio Zoologico Italiano, 52, 169–176. Liaci, L., & Sciscioli, M. (1969). La riproduzione sessuale di alcuni tetractinellidi (Porifera). Bolletino di Zoologia, 36, 61–70. Loeng, H., Mork, M., & Slagstad, D. (1992). Fysisk oseanografi. In E. Sakshaug, A. Bjørge, B. Gulliksen, H. Loeng, & F. Mehlum (Eds.), Økosystem Barentshavet, (pp. 23–42). Norges Allmenvitenskapelige Forskningsra˚d. Malmberg, S.-Aa., & Kristmannsson, S. S. (1992). Hydrographic conditions in Icelandic waters, 1980–1989. ICES Marine Science Symposium, 195, 76–92. ¨ rnba¨ck-ChristieMonniot, C., & Klitgaard, A. B. (1994). A new incubatory mode in an ascidian: redescription of Molgula mira (A Linde, 1931). Ophelia, 40, 159–165. Nilsen, T. (1983). Influence of the Greenland-Scotland Ridge on the geological history of the North Atlantic and NorwegianGreenland Sea areas. In M. H. P. Bott, S. Saxov, M. Talvani, & J. Thiede (Eds.), Structure and development of the GreenlandScotland Ridge (pp. 457–478). Plenum Press. Nørrevang, A., Brattegard, T., Josefson, A. B., Sneli, J.-A., & Tendal, O. S. (1994). List of BIOFAR stations. Sarsia, 79, 165–180. Rezvoj, P. (1928). Contribution to the fauna of Porifera in the Barents Sea. Transactions of the Institute for scientific Exploration of the North, 37, 67–95 (in Russian). Rice, A. L., Thurston, M. H., & New, A. L. (1990). Dense aggregations of a hexactinellid sponge, Pheronema carpenteri, in the Porcupine Seabight (northeast Atlantic Ocean), and possible causes. Progress in Oceanography, 24, 179–196. Sainsbury, K. J. (1988). The ecological basis of multispecies fisheries and management of a demersal fishery in tropical Australia. In J. A. Gulland (Ed.), Fish population dynamics (pp. 349–382). London: Wiley. Schott, G. (1912). Geographie des Atlantischen Ozeans. Hamburg: Verlag von C. Boysen 330 pp. Schulze, F. E. (1900). Die Hexactinelliden. Fauna Arctica, 1, 85–108. Spa¨rck, R. (1929). Preliminary survey of the results of quantitative bottom investigations in Iceland and Faroe waters, 1926–1927. Conseil permanent international pour lÕexploration de la mer, 1–28. Steenstrup, E., & Tendal, O. S. (1982). The genus Thenea (Porifera, Demospongia, Choristida) in the Norwegian Sea and adjacent waters; an annotated key. Sarsia, 67, 259–268. Stro¨mberg, J.-O. (1989). Northern Svalbard waters. In L. Rey & V. Alexander (Eds.), Proceedings of the 6th conference of the Comite´ Arctique International 1985. (pp. 402–426). E.J. Brill.

98

A.B. Klitgaard, O.S. Tendal / Progress in Oceanography 61 (2004) 57–98

Tchernia, P. (1980). Descriptive regional oceanography. Pergamon Marine Series (vol. 3). Oxford: Pergamon Press 253 pp. Tendal, O. S., & Klitgaard, A. B. Taxonomy and distribution of the Geodiidae (Astrophorida, Demospongiae) in the northernmost Atlantic, including the Greenland-Norwegian Sea. Zoological Museum, University of Copenhagen, Denmark, unpublished. Thomsen, H. (1938). Hydrography of Icelandic waters. The Zoology of Iceland, I, 4, 1–36. Wagoner, N. A., van Mudie, P. J., Cole, F. E., & Daborn, G. (1989). Silicious sponge communities, biological zonation, and recent sealevel change on the Arctic margin: Ice Island results. Canadian Journal of Earth Sciences, 26, 2341–2355. Ware´n, A., & Klitgaard, A. B. (1991). Hanleya nagelfar, a sponge-feeding ecotype of H. hanleyi or a distinct species of chiton?. Ophelia, 34, 51–70. Wendelbo, P. S. (1970). Hydrografiske forhold i Trondheimsfjorden 1963–66. Thesis, Institute of Geophysics, University of Oslo, Norway, 98 pp (in Norwegian). Westerberg, H. (1991). Benthic temperature in the Faroe area. Department of Oceanography, University of Gothenburg, Sweden. Report 51, 19 pp. +3 maps. Zenkevitch, L. (1963). Biology of the seas of the USSR. Interscience: New York 955 pp.

Charts Swedish Chart, 93 (Skagerrak, o¨stra delen). Swedish Chart, 935 (Inloppen till Stro¨mstad). 1977. Nautical Charts from the Icelandic Hydrographic Service, 31, 41, 51, 61, 71 and 81. Norwegian Fishery Chart, 552 (Vestera˚len – Vest Finmark – Bjo¨rno¨ya). Norwegian Fishery Chart, 559 (Nordsjo¨n, nordre blad).