Salinity stratified benthic macrofaunal communities and long-term monitoring along the west coast of Sweden

J. exp. INUI’.Biol. Ecol.. 1979, Vol. 37. pp. 17s-203 0 Elsevier’North-Holland Biomedical Press

SALINITY STRATIFIED BENTHIC MACROFAUNAL COMMUNITIES AND LONG-TERM MONITORING ALONG THE WEST COAST OF SWEDEN

RUTGER Swedish

ROSENBERG’

Water and Air Pollution

and

PETER

Research Laboratory,

MILLER Gothenhurg.

Swede11

Abstract: Benthic macrofauna was quantitatively sampled in 12 coastal areas along the west coast of Sweden in 1971-1976. The Baltic Current creates a halocline at zz 15 m depth which acts as a barrier between two differently structured benthic communities, one of which has a wide extension along the coast below the halocline and the other above the halocline. Physical and chemical factors. e.g.. variations in salinity and temperature. have a great influence on the fauna1 structure above the halocline. whereas biological processes are the main determinating factors of the fauna1 composition in the comparatively more stable environment below the halocline. The sub-halocline community contains significantly more species (600;). a significantly higher mean abundance (4200 compared with 2000 ind. m-‘). and a significantly greater mean biomass (146 compared with 71 g m -’ wet wt) than that above the halocline. Diversity measured by the Shannon-Wiener formula and its evenness had approximately the same means in both these habitats, 3.3-3.7 and 0.62. respectively. Four of the areas investigated in 1976 were also studied in the 1920’s by approximately the same methods. The number of species. abundance, and biomass were significantly greater in the recent samples than in those taken half a century ago. and the community structures differed between the two periods. These differences are attributed to seasonal and natural long-term changes and different methods in processing the samples obtained. It is concluded that the halocline is a habitat divider and creates a vertical discontinuity for benthic communities on the west coast of Sweden.

The structure and function of the marine ecosystem along the Swedish west coast, which is considered a part of the North Sea, is greatly influenced by the Baltic Current going northwards towards Norway. This low salinity current stratifies the water column and lies on top of the deeper oceanic water. The discontinuity between these two water masses. the halocline, is normally found at depths of between 10 and 15 m (see Svansson. 1975). The salinity above the halocline may fluctuate from almost fresh water locally, or from about lo%, up to oceanic water salinities. with the greatest variation in the southern parts of Sweden and close to the surface. Below the halocline the salinity is rather stable and. at least in the northern parts. normally above 30x, and usually around 34 %,,.Long-term measurements over ~30 years in the Gullmarsfjord and west of Gothenburg (Fig. 1) show that the 30 %,-isohaline has a fairly stable vertical ’ Present

address:

Institute

of Marine

Research. 175

Lysekil.

Sweden

KUTGEJR

176

ROSENBERG

AND PETER

t I

1 30 km

t j i,56” i

COPE

MILLER

SALINITY-STRATIFIED BENTHICFAUNA

Fig. 1 (cont.).

177

178

RI.ITCiERROSENBER(;ANDPETER

MGLLER

position at x I5 m (Figs 29and 30 in Svansson. 1975). Thus. the marine sublittoral communities above the hakocline encounter great variations in salinity and temperature, whereas those living below this discontinuity encounter a more stable envirctn ment. The tidal amplitude is ~25 cm. Benthic quantitative sampling on soft bottoms in this region began with the classical work by Petersen (c’.~.. 1913. 1924) and was later followed by Molander ( 1928. 1962) and Lindroth (1935) who sampled several coastal areas north of Gothenburg. More recently. the most extensive studies have been concentrated in the Saltkallefjord in the inner parts of the Gullmarsfjord (Fig. 1 : 4) where the structural changes of the benthic communities have been studied in relation to increasing pollution (Leppakoski. 1968. 1975; Bagge. 1969a.b) and to pollution abatemeru (Rosenberg. 1971-1973. 1976). Between 1971 and 1976 studies have been made of the benthic macrofaunal corn-munities in 12 geographically separate areas from the Abyfjord in the north to tltc Sound between Denmark and Sweden in the south (Fig. I). Four of‘ these arca> were also investigated on the same sites by Molander (1928, 1962) in the 1920’s. The aim of this investigation was basically two-fold: 1) to give a comparative analysis o!‘ the present macrobenthic fauna1 structure in the areas studied. and 2) to analyst the long-term changes of the benthic communities in four of these areas over a 50-year period. The influence of the Baltic Current as the main determinant of the conrmunity structure will be discussed. About 400 different taxa are included in thus material. This is the first time benthic communities from such a large area on the west coast of Sweden have been compared. Recently, benthic communities from 1.” areas along the Baltic coast of Sweden were described (Landner rl al.. 1077).

MATERIALAND METHODS

All material collected was sieved through 1 mm meshes. The residue was preserved in 702, ethanol and sorted under a microscope. Twenty of the stations in the Abyfjord. the Gullmarsfjord. the ELI&fjord and in the Stigfjord. investigated by Molander (1928. 1962) in the IY2O’s. were re-sampled in 1976. For comparative reasons the same methods were used: a 0.1 m’ Petersen grab (50 kg) and three samples per station. The macrofauna in the other eight areas was sampled by a 0.1 m‘ Smith McIntyre (SM) grab (70 kg) and five replicates were taken at each station. except at Stations BIO and B12 in the Byfjord where ten replicates were obtained. 7‘11~ sampling efficiency of the two grabs was compared by taking replicates with the SM grab at StationsAY. E4. and S3 where otherwise the Petersen grab was used. I‘hc material collected by the SM grab at these stations was only used for this comparison. The biomass as wet weight was obtained after blotting the preserved animals on filter paper and the wet weights for the different animal groups wcrc transformed to dry weights (excluding shells and calcareous deposits) by the fb!-

SALINITY-STRATIFIEDBENTHICFAUNA

179

lowing conversion (e.g.. Thorson. 1957 ; Lie. 1968) : polychaetes 0.14. molluscs 0.06, echinoderms 0.028. crustaceans 0.04. sipunculoids 0.13 and nemerteans 0.133. The particle size of the sediments was analysed by a mechanical sieve shaker followed by sedimentation rate determination of the finer fraction. At some stations the sediments were classified only subjectively in the grab. The classification was made according to Buchanan (197 1). The information diversity index (Shannon-Wiener) was calculated as H = -

1 P, log1 P, I

where P, = proportion of the abundance (dominance) of species ‘i’. s = number of species and its evenness as J = H/H,,,, (H,,,,, = log, .s). ‘Percentage fauna1 similarity’ (index of affinity) at all pairs of stations was calculated as a sum of the smaller dominance percentages of each species common for both stations being compared. ‘Percentage species similarity’ was calculated as (c x lOO)/(a + h -c). where (I and h are the number of species at the first and the second station, respectively, and c the number at both. These two types of similarity values were further sorted by Mountford’s (1962) classification method : the highest index value was selected and the pair of stations corresponding to this value were combined to form a single group: the indices of similarity between this new group and each of the other sites were evaluated according to the definition of the index between groups of sites. In this way a new reduced table of indices was obtained. The index with the highest value in the reduced table was then selected and the procedure repeated. The results are presented in dendrograms. Taxonomic authorities when not indicated are the same as given by Pearson ( 1970 : Appendix I).

COMPARISONBETWEENTHEPETERSENANDSMITH-MCINTYREGRABS

The Petersen grab was of the same kind as that used by Molander (1928. 1962) and presumably of about the same weight (50 kg). The Smith-McIntyre grab was loaded to 70 kg. Three replicate hauls were taken with each of the samplers from an anchored boat in the Abyfjord at Station A9. in the Elliisfjord at Station E4, and in the Stigfjord at Station S3 (Fig. I). The Smith-McIntyre grab takes a greater sediment volume than the Petersen grab and the number of species. abundance. and biomass obtained by this grab were also higher (Table I). The only exception was the abundance at Station S3. which was similar in both grabs. The oxygen at this station dropped drastically just above the bottom between 14 and 15 m from 12.2 to 3.5 mg 1-I. Low oxygen concentrations have been shown to concentrate the benthic animals close to the sediment surface (e.g., Pearson & Rosenberg. 1978). which suggests why a deep penetration by the grab at this station did not collect more macrofauna.

180

RL’TGER

(‘omparison

between matetul

and Smith-McIntyre

grab ISM)

ROSENBERG

obtained

AND

PETER M6Ll.E.R

I

m IY76 in three samples by a 0.

170 kg): the sediments were subjectively

m’ Petersen prah (P) 150 kg! clwilicd

a\ mainly

\ilt \rill:

\hcll debris

_~^_

-___

- .-. . .

Station5

I’

SM

I’

CM

!’

\\l

The percentage increases in numbers from the Petersen grab to the Smith-Mclntyrc grab were for number of species from 13 to 15”,,. for abundance from 45 to HI”,, (S3 excluded). for biomass as wet weight from 33 to 88”,,. and for biomass as dr! weight from 25 to IOO”,,. The diversity was rather high and similar between rhc grab samples.

DESCRIPTION 0t.T~

AREAS S-I-UDIFD AND THEIR

DOMINAKT

SPECKS

A brief description of the areas investigated listed from north to south (see Fig. I t is given below and the dominant species are tabulated. In each tabulation in rhi\ section the three numerically dominant species al each station are included together with their abundance per m’ when also present at the other stations in the arcii. A complete list of total quantitative data from all stations studied in the 1970‘s ih given in Table II. The salinity values in the areas are taken from Anonymous ( 1970). if not otherwise stated. and give only rough approximations. Oxygen concentration was routinely measured at the benthic sampling stations and was >4 mg;l if no special comments are made. For simplification purposes the halociine is given ii fixed position at 15 m and depths < 15 ni are considered above the halocline. and > 15 m below the halocline with comparatively more stable environmental couditions.

TARLC

II

Quantitative data and diversity of the macrobenthic communities at all stations investigated in the 1970’5: number of species is in relation to sample area and numbers of individuals and biomass are per m’: P. Petersen grab; SM. Smith-McIntyre grab. Biomass

No. of species

No. of

wet wt

dry wt

Grab

Sample area (m’)

ind.

(g)

(g)

H

J

P P P P SM SM SM SM P P P P P P SM SM SM SM SM SM SM SM P P P P P P P P P P SM SM SM SM SM SM SM SM SM SM SM SM SM SM SM SM SM SM

0.3 0.3 0.3 0.3 0.5 0.5 0.5 0.5 0.3 0.3 0.3 0.3 0.3 0.3 0.5 0.5 0.5 0.5 0.5 I .o 0.5 I .o 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

35 55 39 60 34 33 51 67 68 50 60 65 65 72 60 51 55 60 40 38 27 31 38 37 24 73 23 32 13 34 27 20 65 66 69 85 55 75 74 77 37 54 60 50 36 60 35 29 33 18

2075 5 068 2 700 4103 29 903 65 294

134 100 52 128 96 164 24 103 227 182 71 115 135 92 90 152 198 I 04 194 99 I7 306 137 25 167 210 49 85 61 210 11 5 221 192 161 110 369 119 192 89 101 160 23 28 63 49 340 590 105 90

7.9 5.1 3.3 5.5 12.7 18.4 1.7 7.0 Il.7 12.6 7.1 6.1 6.1 4.6 5.0 6.8 11.7 6.0 8.0 8.4 I.2 19.7 7.1 3.1 5.3 12.5 4.0 6.8 3.5 12.9 1.0 0.4 16.8 8.4 8.5 8.8 22.8 5.5 8.2 5.4 13.0 12.6 2.1 1.9 4.1 3.6 24.1 32.9 6.8 7.6

3.6 3.3 3.3 3.9 1.8 1.6 3.8 4.6 4.6 4.1 4.8 4.2 4.0 3.9 2.7 2.3 2.7 3.8 4.1 3.3 3.6 3.0 1.4 4.2 3.5 4.9 3.1 2.0 1.2 0.7 3.7 3.3 3.8 3.6 3.3 4.3 3.5 3.8 3.5 4.1 1.9 3.3 4.2 4.2 0.3 3.6 1.5 1.9 2.6 1.4

0.69 0.56 0.64 0.66 0.36 0.32 0.67 0.76 0.77 0.71 0.x2 0.69 0.66 0.64 0.46 0.40 0.46 0.63 0.77 0.61 0.75 0.60 0.27 0.80 0.76 0.79 0.68 0.40 0.34 0.14 0.78 0.77 0.63 0.59 0.55 0.67 0.60 0.62 0.57 0.66 0.36 0.57 0.70 0.74 0.05 0.60 0.30 0.39 0.54 0.32

Depth Area

Station

Abytjord 2:

Lysekil

Gullmarsfjord

Saltkallefjord

Bytjord

Elliistjord

Stigtjord

Askeriifjord

Hakefjord

Gothenburg

Askimsvik The Sound (iiresund)

!;0 LYI LY2 LY3 LY4 G34 G38 G39 G40 G47 GSO L6 L9 Lll Ll2 Ll8 BlO Bll Bl2 El E2 E3 E4 s3 s4 S28 s30 S36 s37 A3 A6 Al0 A13 Al4 HI H2 H3 GO1 GO2 GO3 GO4 M61 M7l 01 02 ii3 04

Year

1976 1976 1976 1976 1975 1975 1975 1975 1976 1976 1976 1976 1976 1976 1974 1974 1974 1974 1974 1971 1971 1971 1976 1976 I976 1976 1976 1976 1976 1976 1976 1976 1975 1975 1975 1975 1975 1976 1976 1976 1975 1975 1975 1975 1973 1973 1975 1975 1975 1975

(m)

II 17 16 27 8 4 8 12 55 48 13 22 31 32 21 25 30 33 44 7 I1 8 II 8 7 I6 15 10 13 II 10 6 38 20 27 38 6 45 39 37 12 9 10 10 6 7 IO 10 14 9

Diversity _

1270 1068 2254 2 098 926 3 130 3 300 3 800 7950 8 176 6 020 3812 1374 895 408 1245 3610 713 243 2 767 2031 3 526 I 329 8791 789 410 5 532 5 300 5 576 3 828 2 132 2 488 4910 4152 48 625 10253 2513 1254 19672 4880 18982 15324 3270 15614

1x2

KI:T(;FR

ROSENBER(;

AND

PFTFR MOLLFR

The Abyfjord (A-stations) is surrounded by farm land. and gets successively shallower towards the inner par& The salinity at Station A7 at I I m tluctuatcs aroumi 28X. whereas at the other stations below the haloclinc it is =30-34g,,, The scdiments were subjectiv’ely classified as predominantly silty with shell debris. The t(_)Ilowing dominants were recorded at the different stations (also investigated I>! Molander. 1962) in numbers per m-:

‘I,,

of

62

total

---

71

6X

6X --.--_.

Amphiuru~fil~formi.sdominated by wet weight at each of the stations below the halocline. Nucula nitidosa and Ah-u nirkfa were abundant at all stations.

LYSEKII

The Lysekil (LY) stations were close to the town of Lysekil and separated from the rest in the Gullmarsfjord for practical reasons because they were not studied m the 1920’s. Four stations were investigated above the halocline (22-32%, S). Station4 LYI and LY2. polluted by sewage and organic material. were situated in the boar and fishing harbours. Stations LY3 and LY4 were located nearby in an unpolluted bay. Sediment analyses showed that Station LYI was predominantly clayey sill. Station LY2 silty sand. and Stations LY3 and LY4 silt. The following dominants were recorded (numbers per rn? :

SALINITY-STRATIFIED

BENTHIC

FAUNA

183

Station Depth (m)

LYl 8

LY2 4

LY3 8

Nematoda

16876

40 800

350

7 604 3 250 1052

7 330 3 484 12466

34

_

28 12 8 240 142

Capitella capitata Scolekpis, fi4liginosa Peloscole.~ henedeni Pomatocrros triqueter Nepht)‘s hombergi Tellina,f&da

‘z of total

LY4 12

10 4 4 244 128

-

86

98

96

61

45

Stations LY I and LY2 were dominated by typical opportunist species frequently found in organically polluted areas in extreme numbers (Pearson & Rosenberg. 1978). Capitella capitata had the highest biomass at these stations (25 and 21 g wet wti0.5 m’). THE GULLMARSFJORD

In the outer part of the Gullmarsfjord five stations (G) were investigated below the halocline (32235x, S). and one (G39) above the halocline (22232x, S). The fauna at these stations was studied by Molander (1928) in the 1920’s. The sediments were subjectively classified as silt at Stations G34. G38. and G47. and as silty sand with gravel and shell debris at Stations G39, G40. and G50. Dominants were (numbers per m?) : Station Depth (m)

G34 55

G38 48

G40 22

G47 31

G50 32

G39 13

Heteromastus,fil~formis Amphiura chiqjei Amphiura,fil~fbrmis

300 256 243

103 330 360

57 _ 696

_ 30 653

_ 147

_. ._

Prionospio malmgreni A4ysella bidentata Onoba vitrea (Montagu)

117

243 13

246 676

80 813

846 946

20

_

236

10

293

3

_

Abra nitida Ascidiella aspersa (0. F . Miiller) Pomatoceros triqueter Tellina.ftibula

93

60

157

196

393

7

_

10

_

_

_ _

_

__

_

_

_ _

127

_

83 90

“/, of total

45

64

59

63

62

35

184

RUTGER

ROSENBERG

AND PETER

MijLLER

Amphiuru,#~~~f~rmi.s.Prio~~~~~~?i# ~~u~~~~rei~~. and Abm &ida were c~m~nnn at all stations below the halocline. whereas above the haiocline epifaunai species dominated. Biomass as wet weight was dominated by the echinoderms: at the deeper Stations G34 and G38 by ,~rnp~?i~r~~ c~~j~je~ ( 16 and 24 g/m’. respectively) and Br~~~.~~)p~~~~ /u+&w (80 and 34 g) and at the other stations below the halocline by Amphima fltl~ftirmi~ (average 30 g/m?. I-HE SALTKiiLLEFJORD

The Saltk~lle~jord ~L-st~~ti[~rls~ is a fjordic estuary in the inner part of the Gullmarsfjord. The salinity below the halocline varied between a30 and 35 :&. The sediments at Stations L6 and LY were sandy silt and at Ll 1. L12 and L18 clayey silt. The benthic fauna in this fjord has been described in several publications during almost healthy environmental conditions (Molander. 1928; Lindroth. 1935). during periods of pollution t Lep~k~~ski. 1948. 1975; Bagge. 1969a). and pollution abalement (Rosenberg. 1971- 1974. 1976; Olsson et (II.. 1973; Pearson & Rosenberg, 1976. 1978). Dominating species in 1974 are listed below (numbers per m’):

“” Of tOtdl

79

87

82

61 -

311 --

Biomass was dominated by Br~.s~~op~i,~ ~v+~#~rtr (128 g/m?) at Station LI 8. whereas Amphiula,filifbrmi~~ was the dominant at the other stations (average 30 gim’). THE BYFJORD

At the entrance to the Byuord (B-stations) is a sill at 12 m depth. which limits the periods of water exchange below the ha&line to less than once a year. As a result the oxygen below this level is depleted and no macrofauna has been found below 17 m (Rosenberg. 1977). The salinity above the halocline is 22-.30 %. During this investigation (Olsson ef al.. 1973 ; Rosenberg r! itI.. 1977) the fjord was polluted principally in the inner areas by sewage from the town of Uddevalla and a shipyard. The sediments at Stations BIO and Bl I were mainly silt, but there was silty sand at Station B12. The following dominants were recorded in numbers per m’ :

SALINITY-STRATIFIED

BENTHIC

185

FAUNA

Station Depth (m)

BlO 7

Bll 11

B12 8

Neph t?‘s hornhergi

302 157 134

16 92 22

346 250 159

10

84

248

4

52

6

68

65

81

Phoronis miilleri Selys-Longchamps Philine sp . Pectinaria

koreni

Ophiura te.yturata

“” of total

C?prina islandica dominated the infaunal biomass at Stations BlO and B12 with 3 1 and 246 g/m?. respectively.

THE ELLGSFJORD

The Ellosfjord (E-stations) is shallow (lo--l6 m) and the sediments at all stations smelled of hydrogen sulphide. probably as a result of decaying Zostera (c$. Molander. 1962). Oxygen concentrations were. however. > 10 mg 1-l in the bottom water at the time of sampling. The salinity in the area is similar to that in the Gullmarsfjord (22-32 %,). The sediments were subjectively described as organically enriched silt at Stations El. E2. and E3. whereas Station E4 had a coarser substratum with shell debris. The benthic fauna was studied in 1927 at the same stations (Molander, 1962). The following species were numerically dominant (numbers per mz) :

Station Depth (m) Corbula gibba Echinocardium cordatum HeteromastusJil~formis Mysella bidentata Terebellides stroemi Chaetozone setosa Scalibregma injlatum

‘7, of total

El 11

E2 8

E3 7

E4 16

2920 303 37 20 7

103 13 73 130 77 _

43 83 _ 20

33 3 346 80 10 336 226 38

10

3

3 _

91

56

62

186

RI:~l~<;t.K ROSENBERG

Station diversity

E4 is just below the halocline than the other stations

A&D

PETER Mijl.l_tR

and accommodates

(Table

more species and a hiphcr

II). The abundances

were low (7 I.3 and 243 ind. m’. respectively)

probably

at Stations

E:! and I :

bccausc 01‘ the /lo.~rc~ dcbri\

on the bottom.

rttf:

s-rtc;k.foRn

The northern part nl’ the Stigtjord (S-stations) is shallow- with %o.v/c~ mrado\\~ Water exchange is limited IO two narrow passages in the western part and 10 c)I:~ very narrow passage southeast of Station S37 (Fig. I : 7). Because of this. the oxygc~~ concentration may occasionally dtxrease drastically just above the bottom: v,y.. (,!I the day of fauna1 sampling. Stations S3. S4. and S30 had 3.5. I .9. and 1.8 mg I respectively. The sediments at all stations smelled 01‘ hydrogen sulphide and WCIY enriched by %o.srrt~r debris. Salinity at 10 to I5 m depth in the Stigtjord is according to hydrographical data from the Fishcrh Board of Sweden ( IO71 l9?5). betwccl: 70 and 32 X,. The same stations ;I\ listed below wcrc also sampled 111 19)3i 102~ (Molander. 1062). The following abundant specks \verc rccordcd (numbers per 111 I

s3 15

S30 II 100

00

Xl39 I IO

30 96

All stations in the Stigljord were salinity. temperature. and oxygen with few species ( 13-34) and a low compared with communities below

situated above the halocline and variations 111 concentration resulted in benthic communitlc< biomass (5.--85 g/m-. excluding A/m rrlhr at S2U) the haloclinc (Table II).

SALINITY-STRATIFIED

BENTHIC

FAUNA

187

THE ASKEROFJORD

Waste water from a petrochemical centre at Stenungsund is discharged into the Askerofjord (A-stations) east of Stations A3 and A6. Changes in the benthic communities in the area have been studied by scientists from the Kristineberg Marine

Biological

included

Station

here seem rather

since 1962. The effect of pollution unaffected

(Miiller.

unpubl.).

is local and stations

The salinity

at the shallow

Station Al4 is x20-30%, and at the deeper stations 28-34x,. The sediments were subjectively classified as predominately silt. with shell debris at Stations A 10 and A 13 and enrichment by decaying 2o.ster.a at A 14. The abundance of some dominants in 1975 were as follows (numbers per n?) :

Station Depth (m)

A3 38

A6 20

A10 27 .~~

Al3 38

Ahra nitida Trochochaeta multisetosa Sosane gracilis (Malmgren) Mj?sella hidentata Amphiwa, fil~ftwt~~is Prionospio malmgreni

1534 770 638 98 288 362

192

118 2 950 1414 1354 240

542 154 384 80 134 796

750 440 182 ~__~ 64

231 716 604 124

Neplq~s Izomheqi Coahula gibha Philinr sp.

10 6 4

13 10

50 6

2 22 2

I’:,of total

67

71

74

55

Below the halocline

the dominants

are the same at all four stations.

whereas

Al4 6

2 .~

Station

Al4 at 6 m accommodates a different fauna. The biomass below the halocline was dominated by Amplziura,jr”l~f~fbrmi.s.The high biomass at Station Al4 (Table II) was due to seven big M~~tilus edulis; if they are excluded. the wet wt was 55 g/m’. THE HAKEFJORD

The Hakefjord (H-stations) is the southern extension of the Askeriifjord and the central channel is 2CL25 m deep. The fauna1 communities presented here were from the deep parts. 3745 m. where the salinity was 32-35x,. The sediments were subjectively classified as grey silt at all stations with shell debris at Station H 1. The following dominants were found (numbers per m’) :

188

RUTGFR

ROSENBERG

AND PETER

MBLLER I__-___

Station

Depth 0-n)

H1 45

HZ 39

.

.

.

-,

f-i.? 37

THE GOTHENBURCi

The Gothenburg area (GO-statiol~s) is poIIuted by wastes from the river and !qy shipping. and the structure a& regression of the benthic eo~~rn~n~ti~s during this century have been studied by Swedmark ( 1Rib), Tulkki (1968). Bagge fX969b). OIsson CJ~ ai. (1973) and Nyholm et ul. (1977). All stations in this study were located abovc the ha&line. The salinity at the polluted Station GO1 varies between 5 and 20”~. whereas the others have a salinity of IX-28 X0 (Anonymous. 1972). Sediment analyses cIassified Stations GUI as s&y clay. Station GO3 as clayey sand. and Station; GU2 and GU4 as sand. The dominants with numbers per m” were as follows : GO1 I?

GO2 9

19 736 15006 12196

28 910 -.3644 1700 970 50 132

_ 56 10 56 .I_ -

I_

-11

GO3 10

GO4 ItI

I4 8

1 _.

5% x 332, 384 ._

4 97

73

52

2 40 250 226 94 49

“.

SALINITY-STRATIFIED

BENTHIC

FAUNA

189

Station GO1 was dominated by typical pollution-resistant species. The other stations had dominants divergent from the other areas along the coast. The populations of Ampharete balthica. NephtJss spp. and MJY~sp. were predominantly juveniles. The genera Nepht?xs included mainly N. homhergi and N. incisa. but also N. caeca. N. ciliata. and N. longesetosa. THE ASKIMSVIK

This bay (M-stations) shoals rather evenly towards the inner parts and the water exchange is good. The salinity at 6 m varies between 22 and 32 %,,.The sediments at Stations M61 and M71 were sand. The northern narrow part of the bay (Valen) was polluted by sewage and heavy metals during this investigation. but the effects on the bottoms in the Askimsvik were only slight (see Cato et al.. 1975. 1978; Cato. 1977). The following species had the highest numbers per m’ :

Station Depth (m)

M61 6

M71 7

Hjdrobia spp. Macoma balthica (L.) Neph tys caeca (Fabricius) Bittium reticulatum Corbula gibba

19 168 210 54 _ 2

1950 96 14 478 430

99

61

0,/O of total

About 85~~~of the Hydrobia spp. was H. ulvae and the rest was H. ventrosa. THE SOUND @RESUND)

The hydrographical situation in the Sound (o-stations) is complicated and occasionally there are two haloclines. The variations in salinity are great and at the sampling stations x10-32%,. Analyses of the sediments showed Stations 01 and 03 to be silty sand, Station 04 sand. and Station 02 gravelly sand. Stations 01 and 02 were situated outside the outlet from a sewage purification plant. whereas the other stations were not directly affected by pollution. The benthic communities in the Sound have more recently been studied by Henriksson (1968. 1969). In this investigation dominants were found to be the following (numbers per mz):

190

Rl~l‘CjFR

ROSENBFRCi

AND

PETER MOLLER

02 IO 10576 6 SIX I 454 7 188

1

I48 1634 436 330

31(: lclr

914’

Several of the species listed from the Sound have not been reported as dominant\ in the other areas. The species composition seems to be determined by the IOU and variable salinities in combination with pollution. MMYMCIhaltlticrt was a common species at Stations ijl. 02. and 03 in numbers of3Ob380 per m’ and was one 01‘rhc dominants in biomass with wet weights of between 36-94 g.:m^.

The similarity of the benthic communities at all pairs of stations presented above has been analyscd. Two complementary methods have been used: I) -Percentage fauna1 similarity’. which takes the species abundance values into account in the analysis. and 2). ‘Percentage species similarity‘. which is a measurement of the number of species shared by pairs of stations (see. Johnson & Brinkhurst. 197 i : Rosenberg. 1972. 1973). Each of rhesc measurements has its limitations and advantages. The first neglects rare species which the second over-values. and used together they are complementary. The results have been clustered for simplification and are shown in two dendrograms (Figs 2 and 3). In the fauna1 similarity dendrogram (Fig. 2) four groups of stations can be distinguished. Group A contains stations below the halocline and Group B stations above the halocline. Benthic communities clustered m Group C were from the two southernmost areas and dominated by H~drohitr spp. in high numbers. and those included in Group D were dominated by pollutiontolerant species and nematodes. The three most conspicuous species below the halocline were Atnpltiurcr fil+vwti.s. M,~~.vcll~tbidmttrru. and Ah ttitith. They u’c‘rc. with few exceptions. not ranked among the ten dominants in any arca above ttlc halocline. Dominants above the halocline included a larger group of species of~vhich

SALINITY-STRATIFIED

BENTHIC

FAUNA

191

lLY2 D

*L-y1 03 *GO3 l

------??----

:

--------____ 7

-_-..-

;;’

1

. S28 l . .

f

El E3 E2

-.__-

. . . l * .

537 Al 4 Bll

---

.

-__-2

.

____1__1 __.--

I.18 Al3 A.3

I

1n

w Percentage

Fig. 2. Dendrogram

t

2

fauna1 similarity

ofpercentage fauna1 similarity in the 1970’s: the symbols of the stations in Table II; l . station situated above the halocline (depth < 15 m).

are explained

192

RI:‘I‘<;f:R

ROSENRERC;

AND

PFTI:R

Mol.1 F.R

. G39------_____ lLY2 l LYl *GO4

.LY4 .LY3

---. --___-

._._.. _____..

*GO2 aGO1 --.

-..- ---

F

. S28--_--_. . S30__.~_._____

._. .._

. 6 1 1 -~. ._.__.~ . rj12_-. -. BlO-. ------------------___ G50---.G4 7 __. __..

E

G 3 8-_

.__..

G34-__

L , &-__

16

_

..__

_ .._..... I-1-1 100

_

.-_

__..__

-‘-1 60 40 20 80 Percentage species similarity

0

SALINITY-STRATIFIED

the following

BENTHIC

were the most conspicuous:

tinaria korrni, and Philine

sp.

These

FAUNA

193

Nepht~,s Izombugi. Corbula gibho. Per-

species

were

never

ranked

among

the ten

dominants in any area below the halocline. The species similarity dendrogram (Fig. 3) shows approximately the same division with similar species below the halocline (Group E) and above the halocline (Group F). Within these two groupings the withinarea species similarity is slightly more pronounced than in the fauna1 similarity analyses. e.g.. A-. M-. and o-stations. Diversity values measured by the Shannon-Wiener function (H) were between 0.3 and 4.8 above the halocline and between 2.3 and 4.9 below the halocline (Table II). The low diversity was due to extreme dominance by H>drobiu spp. Evenness (J) similarly showed the broadest range above the halocline with values of between 0.05 and 0.82 compared with between 0.40 and 0.80 below the halocline. A comparison of number of species. abundance. biomass. and diversity between the benthic communities above and below the halocline shows some general differences (Table III). It must be stressed that the number of samples was not always TArlLt III Comparison of number of species per sample area (see Table II). abundance. and biomass per m’. and ‘diversity between benthic macrofaunal communities above (A. II = 20) and below (B. II = 21) the halocline at -15 m: Stations LYI. LY2. GOl. G02. M61. 61-04 excluded; * C~prinu r.~/c~/icr~ at B I2 and ,21~~rilus duli.\ at A4 excluded.

\.t

Mean

Number of species Abundance Biomass. wet wt* Biomass. dry wt* Diversity H Diversity J

the same.

which

A

B

A

39 2005 71 4.7 3.3 0.62

63 4206 146 7.9 3.7 0.62

3 448 13 0.7 0.2 0.04

has a disproportionate

influence

Range B 3 394

II 0.7 0.1 0.02

particularly

A

B

13-67 243 -879 I 5-210 0.4 12.9 0.7-4.8 0.14-0.82

3Y 85 1374 8176 52 727 3.3~~16.X 2.3 4.8 0.40 0.79

on the number

of

the species. and that two different grabs were used (see above). In this comparison the polluted stations (LY 1. LY2. GOl. G02. M6l) and the southernmost region (the Sound) with its extreme abundances were excluded. The general picture is unidirectional: below the halocline there are z60”,, more species and about twice the abundance and biomass when compared with areas above the halocline. The differences are all significant at the 0.01 level. If the same comparisons are made of samples taken with the Smith-McIntyre grab and the Petersen grab separately. the number of species will also be significantly (P < 0.0s0.001) higher below the halocline for both grabs, and the abundance for the Smith-McIntyre grab (P < 0.001). Diversity did not show any significant difference. This is explained by the great influence that dominance has on the H-value. and dominants were present below

194

RI.~‘l’<;I:R ROSEhRERC;

AND

PIYTER MijLLtR

as well as above the halocline. Another method of calculating species divcGt> (L’.K..Sanders’ rarefaction technique) would probably have demonstrated a diffcrcncc as the number of species differed (see Pearson & Rosenberg. 1978). In conclusion. the benthic community structures and abundances along the Sucdish west coast fall into two main groups determined by abiotic rnvironmcntal factors regulated by the halo&e. The variations in temperature and salinity ab~jvc the halocline creates communities with great seasonal fluctuations in abundance. Below the halocline the seasonal variations are small and the communities relativcl! stable. These two groups correspond in the broad sense to Sanders’ ( 196Y) physicall! controlled and biologically accommodated community types. The tluctuationh III abundance are generally regulated by larval recruitment. Above the halocline the communities are ‘open’ and have space available for settlement. The species living in this variable environment have good and bad years of recruitment (Thorson. 1936. 1957). which strongly influences the dominance pattern of these communities. Communities below the halocline are ‘closed’ and the chances of immigrants sur\:iving are far more limited. because of higher biological competition and crowding. Atnphiuru,/i’lr~??j,~ seems to be a key-species in structuring these sub-halocline conimunities. It dominates the bottoms of vast areas between Sweden and Denmark (KC Fig. 1 in Petersen. 1924) and it has recently been shown to be a community-stabilizer during succession (Rosenberg. 1976). Evidence that the sub-halocline communities arc basically biologi&ly controlled was given at the stations sampled in the Hakefjord. Some of the sampling sites dcscribed above were later (in spring 1977) subjected to the deposition of dredged material. The previous community (see above) was wiped out and six months later (in autumn 1977) several typical supra-halocline dominants appeared in that arcd as juveniles. c.x.. Spisdtr .~uh~r~~~~~~r~~ ( I70 ind.:m-). Cot~hrfu xihbu t 1I6 ind.+C). and Abra NI~LI (24 ind. m-‘) together with Priomspio tntrlrngtwi (62 ind.. m’). and .41~11 niridu (32 ind./m’). The species found above the halocline are in general coniparatively shorter-lived than those found below the halocline and they have ;I dilferent reproduction pattern with recruitment every year. As seen from the natural experiment above. the halocline is not a barrier for the larvae of the species abo\:c the halocline; rather. they are bad competitors in the comparatively more stable environment below the habitat-dividing haloclinc. LONG-TEKM

MOKITORINC~

It is well known that cities and industrial concentrations cause local pollution problems in the sea. II is. however. not known if these locally induced elects together have widespread impact on the marine coastal ecosystem outside these areas. An indication of such widespread effects on marine life was obtained by ;i comparison of benthic macrofaunal composition on the Swedish west coast rod+> with that described from some areas half a century ago.

SALINITY-STRATIFIED

BENTHIC

FAUNA

195

All twenty stations in the Abyfjord. the Gullmarsfjord. the Elliisfjord, and the Stigfjord described above were previously investigated by Molander in the 1920’s using the same type of Petersen-grab (Molander. 1928, 1962). We are fairly convinced that we found approximately the same sampling sites about fifty years later. following Molander’s careful description of position and depth. Even the description of the sediments and the occurrence of Zostera debris corresponded in the two investigations. During the investigation from 1923 to 1928 in the Gullmarsfjord the distribution of the associations was very constant with no change from one year to another (Molander, 192k). Detailed quantitative comparisons of the fauna are of little value since the differences are very large. In general 2-3 times more species were recognized in the 1970’s compared with the 1920’s (P < O.OOl),and the difference in abundances was even greater (P < 0.001); in a few cases a ten-fold difference was recorded (Fig. 4). The Number

1 B

20

20I

I

0,

I

of species

40

I

I

Abundance

610 ,

0

0

0

e

l

0

0:

l

l

:-

1lo 0

*

0

l

c 60-

Wet Jr

20I

6

$

1

l l

weight 40

I

Dry weight 60

I

I

T

190

2,O

I

00~

0

l

l

3,o

4,p

l

_:,ooe4Lp_ _T_‘__,_ _-- _.-‘_-e~-_?o---_-:_-_-. -o--- 9 i0

I

d

l

0

l

x-

G- 40 h

15.00

l 0$i% ’ ---__ ,-*--------,_-_*__--__e~_-_-*__ &eee

0

z 40‘a 6

-c-

1000

IL

le

6

_-_-l 0

20

500

80I

0

00

1

l

Q

lo l

00

1

l 0

l

0 0

-e

l

l

0 0

l

e l l

60

Fig. 4. Number of species. abundance. and biomass (wet and dry wt) per 0.3 m’ in relation to depth in 1976 (0) and in the 1920’s (o) (data from Molander. 1928, 1962): the approximate position of the halocline is indicated by a dashed line; biomass of 1 Cyprim i.tlandicu at Station E4 excluded from 1976; quantitative data from the Stigfjord in the 1920’s was lacking from most of the stations.

196

KlJ(;t-.R

ROSC’UHERC;

AKD

PETER

M(jI.L.ER

biomass was also significantly (P ~0.05) greater in the 1970’s. In a few cases (AY. C&IO.E4). when echinoderms and one large C:l*princr isluntlica dominated. the biomay> was higher in the 1920’s. Diversity followed the same trend with greater values in 197h. but was slightly higher at Stations Ax. El. and S4 in the lY2O.s. The structural similarities in the benthic communities between the 1920’s and lY76 have been analysed by percentage fauna1 similarity and percentage spccics similarity indices described above and are presented in two dendrograms (Figs 5 and 6). The fauna1 similarity dendrogram shows six separate groupings of station\ (Fig. 5: A--F). A and B contain shallow-water stations above the halocline (excqt GJ9*). where A represents the 1920’s and B 1976. C and D include stations beln~ .*E3

l*E

F

___-~

2

*(;34_-

_-._

._ -.._---__-

I

---

I-- , j-

E ----------------

-*-G SO-

-.

----

.--l

LG~&____-___-

I-

I

Ii j!

D --------.-------------E4 _

. E

,

-._ ..__

.._._

._

_

_. ._

-.--.

. E3 -.._.. l

E2

. . s 4 .*

s 3

l%EE ~3: E I

%i\7

-

---..

_._. _-_.---

.-.. --.._

_

_.

_.

.._.

--- .;-- - --J

_

.J

_-.__.

...-1--

.-

c_., 100

..-.., _

._.‘_

80 Percentage

60 founol

I

40

20

I

I

0

similarity

Fig. 5. Drndrogram ol’ptxen~apu t’aunal similarity including rwdts t’rom 1976 and thr IYJl‘s from Molandcr. IY_‘H. IYhZ). for further explanation we caption IO Fig. 2

(.J ILI:II~

SALINITY-STRATIFIED

BENTHIC

FAUNA

197

the halocline (except S4). where C is from 1976 and D from the 1920’s. The species similarity dendrogram (Fig. 6) shows approximately the same thing: G and H contain mainly shallow stations and deep stations. respectively sampled in 1976 and I and J demonstrate the corresponding situation from the 1920’s. *SE3

K --

- -

I I

‘NE2 l G3--

---a-------

*G34 *G47 iK;38

J

%50 mG40 *AlO ------------------___ 0x-E 4

- - .-

-

l z:-

I

*%S 4 *X$3 ~ lxE 1

----

‘*A8 - -Es

-:-_..

n

=’

-

l_

---------I----. ,

G50s4

---

_-

.____..

6447 G40-p AlO----__

-.

G

107

80

60 Percentage

40

20

01

species sintiiarity

Fig. 6. Dendrogram of percentage species similarity including results from 1976 and the (data from Molander 1928. 1962: for further explanation see caption to Fig. 2.

1920’s (*)

In the Gullmarsfjord the following species were abundant in 1976. but scarce or not present in the 1920’s: Phoioe minuta, Prionospio ma~rngre~~~. Brada vitlosa. Hc~teromastusJ~l~j~rmis, M~~sellubidentata. and Abra nitida. At Station G34 the following species had decreased in numbers from 1923 to 1976 (per 0.3 m’) : ~ald~zn~ sarsi (I 40 to 12). Me&ma cristata (32 to 12). Terebellides stroemi (17 to i)? and

198

KUTGER

ROSENBERG

AND

PETER MtjLLER

MoIander (1962) did not give complete species lists from Stations S28. 535 and 537 in the Stigfjord. which excludes those from the general fauna1 comparisom, Molander reports. however. a great stability (persistency) in the populations of some‘ type animals over the years 1923. 1924. and 1925. which seems to be rather persistent up to 1976 (numbers per m’):

in conclusion, all these. analyses and the quantitative comparison above clearly demonstrafe that the benthie communities found in the 1920’s are quite dirTerent_ some 50 years later. Does this imply that there have been long-term changes and. in that ease, are these caused by widespread polfution on the Swedish west coast? We suggest two main reasons for the difference: 1) natural long-term and seasonal changes. and 2) different methods in processing the obtained samples, There is no plausible natural reason why the quantity of animals should be that much greater today than about 50 years ago. In our investi~tion the animals were picked out from the preserved sieve residue in the laboratory at 6x rna~i~~t~o~.,w~ereas the old mater&t was pisked on the &eve aboard the ship (see also p. 4% in Thor-son. 1957). As seen from the differences in recorded animals as listed above, several oli the species collected in cons-iderably higher numbers in 1976 are naturally small in size and would be difficult to pick out from the residue on the sieve, e.g.. Pltoi&! ~~~~~~~,P~~~~~~p~~rn~~rn~~~~~. ~~~~~5~~.~~~s ,~~~~~~rrni~~ and ~~~~~~ b~~~~t~~~.2% study the effect of the exclusion of small sized abundant species on the community structure comparison. a Cluster anafysis on percentage fauna1 similarity was made.

SALINITY-STRATIFIED

BENTHIC

FAUNA

199

This was identical to the one presented in Fig. 5. but without the species listed in the legend ofFig. 7. In thisreconstructed dendrogram three main groups are distinguished. where A and B contain shallow and deep stations. respectively. Within these two groups the stations sampled in the 1920’s are grouped together. as before in Fig. 5, but the degrees of similarity have increased from 15 to 28”; among the shallow

B NG50

II

II

z@-+Y 1 --------------------A lws4

It--

I,,,,,,,,,,

100

60

60

40

20

0

Percentage fauna1 similarity Fig. 7. Dendrogram of percentage fauna1 similarity as in Fig. 5. but excluding the following small sized species in the analysis : M~~iockle spp., Cupirrllu capita/a. Hcteromu.sm fil@mis. Pygospio clqam. Pholot’ mirlutcc. Pol~~lora “pp.. P~io~~o.spio spp. Pelo.vcol~~.uhmedewi. and Myselia hidmtrrta.

200

RI?T‘Gk!R ROSENBERG

AUD

I’E-rt:R MiiLLE!R

stations and from IO to 26?,, among the deeper stations. As the small-sized spccles are often abundant their exclusion or reduction in numbers in Molander’s specie> lists explains. at least partly. the quantitative and structural differences. Recorded differences concerning medium-sized and large species should be 1~ influenced by systematic errors. The benthic community structure above the halocline is known to have considerable natural variations due to environmental stress and variable recruitment success among these species (Boesch cr al.. 1976: Roscnberg. 1977). This explains to a certain extent the temporal quantitative differcnccq of species as P.S.. (‘Cahill gihhtr. Ah ulhtr. and T~rdwllicks .srrowti. Reh the haloclinc in the Gullmarsfjord the brittle stars Atnphiuru /ifjfbrtni.v ;~nd .4. d~iapi were rather constant over the 50-year period at Stations G38. G40. G47. and G50. whereas Ah nitidt had increased in recent years. These two amphiuran spec~ctb are known to have stable populations over long periods (Rosenberg. lY76). In contrast. A. ttiridrr has been shown to have great temporal fluctuations (Buchanan (21c/i.. 1974). The amphiuran species had a greater mean weight per individual in tY70 compared with the 1920’s at all stations except one. whereas for .4. rrrritkl the mean weights were much higher half a century ago. which could be a sorting artititcl The high abundance of A. nitich in lY76 was. however. made up by juveniles. whcrcas the difference in biomass by the amphiurans could be due to different age structures in the populations between the 1920’s and 1976. As the brittle stars are sus. ccptible to pollution (see Rosenberg. 1972: Pearson & Rosenberg. 107X) and arc still present in ihe investigated areas below the halocline. this suggests that the othcl changes below the halocline are caused by natural phenomena. Moreover. it is onI\ occasionally that species reported by Molander are not found in 1976. This suggests that the coastal marine environment in these four areas has not yet been affected by widespread pollution to such an extent that the fauna1 changes could be definiteI> ascribed to pollution. In conclusion. the differences in community structure between 1976 and the IYX’s were small following the exclusion of some small abundant species from the cluster analysis. The exclusion of these species was based on the assumption that they were not included in the material from the 1920’s when another method of sorting M:X~ used. The existence of a difference is natural. since the fauna1 structure in these areas will change seasonally and certainly over a period of half a century. The benthic communities studied here have not one fixed stable point. but oscillate around some kind of equilibrium or neighbourhood stability. where the variations are determined by e.g., abundance of predators. success of recruitment. and variation of environmental factors. The significant difference in number of species and abundance hetween these two investigations is probably also due to the difference in sorting technique. Biomass varies from sample to sample. because one or ;I few large individuals have a great influence on the final result. and general differences should. therefore. be treated with care. It may possibly be that a more careful handling ot the grab to get good samples as well as the sorting. also had an influence on the

SALINITY-STRATIFIEDBENTHICFAUNA

201

discrepancy in biomass value. The other possibility. that recent increments in abundance and biomass are indications of eutrophication and organic enrichment. must be dismissed because 1) the number of species has also increased recently. and 2) the community structure and diversity are not in such a disorder as to indicate pollution effects. A few examples of directional long-term changes of benthic fauna1 communities over decades. in the absence of effects of direct pollution. are known from the literature. In a mud bottom area at one site near Helgoland in the North Sea, Rachor (1977) reported a long-term trend of impoverishment of the fauna attributable to the development of anaerobic conditions in the sediment. One suggestion as to the cause of the impoverishment is widespread pollution. Apart from that particular site, the benthic fauna seemed to be unchanged in the Helgoland Bight from 1923 up to 1966 (Stripp, 1969). In Kiel Bay. Arntz & Brunswig (1976) reported f:dunal differences between investigations in the 1920’s and 1975. but the changes were difficult to interpret and might have been due to natural causes. In the central Baltic 28 stations investigated in the 1920’s were re-investigated recently (Cedervdll, in prep.). The results were similar to those found from the Swedish west coast in that the abundance and biomass in the Baltic showed a significant increase lately above the halocline at about 70 m. Below the halocline the benthic communities were recently more impoverished due to oxygen depletion in the deep parts. In the southern Baltic the increased deposition of organic material on the deep sediment was assumed by Schulz (1969) to be responsible for the lowered oxygen concentrations in that area and. as a consequence. the reduction in the benthic fauna over the past 40 years.

ACKNOWLEDGEMENTS

We wish to acknowledge the skillful and valuable technical assistance given by MS A. Ahlfors. MS L. Johdnsson and MS P. Romare of this study. Sincere thanks to go Drs T. Pearson and E. Leppgkoski for suggestions on the improvement of the manuscript. The computer-team at IVL kindly helped us with several calculations.

REFERENCES ANO~\.MOLS, 1970. Hydrographical observations from the fiords of Bohuskn during the years 1X931966. Me&. Hu~,.~f~skelahoratoriet Lysekil, Nr. 77. 259 pp. (mimeo.). AN~NYMCI~S. 1972. Gtitehorgs Vuttenvdrclsarll~~~nin,~ar. Re~ipir~ntundersiiknin~ar dr IY7&1971. Typografia. Gateborg, 210 pp. ARNTT. W. E. & D. BRUNSWIC;. 1976. Studies on structure and dynamics ofmacrobenthos in the western Baltic carried out by the joint research programme “Interaction sea sea bottom” (SFB 95 - Kiel). In. Proc. 10th Europ. Symp. Mur. Bid.. Vol. 2. edited by G. Persoone & E. Jaspers. Universa Press. Wetteren. Belgium, pp. 17-42.

RUTGER

202 B,+G(;L. P..

196%.

Effects

ROSFNBERC;

of pollution

on estuarine

processing industries on the hydrography. rurkindshir.

Bnc;c;r. P..

Julk.. Huyfiwvk.

1969b.

lrrsr

in polluted

PETER

MijLLFK

ecosystems.

bottom

1. Effects of cfllucnts

and fauna of Saltkillefjord

(W.

from

Sweden).

wood.Zf&,rr,+

Skr. No. 228. pp. 3--l IX.

Effects of pollution

fauna communities

AND

on estuarine

estuarinr

habitats

ecosystems.

II.

The

succession of the bottom

in the Baltic-Skdgerak

reglon.

.Wrrwir/trkr/,lltriiI;,

Ju/k.~Htr~.+/ixvk. Irttr.. Skr. ho 118. pp. I IY 130. Botsc.ir. D. b.. M. L. WAS> & R. W. VIWXSII.I\. in. f3uur;~re

BI_x:HAX,~~. J. B.. 1971. Measurement for r/~e srudl. o/.nnlarUtc, bathos. well. Oxford.

Academic

of the physical and chemical environment;

edited by N. A. Helms

bcnthlc commumtlc\

Press Inc.. New York.

& A. D. Mclntyrc.

pp. 177. 1%

sediments. In. :\Ic,/hr~h

1BP handbook

IO. Black-

pp. 30.- 52.

BI!CHANA-X J. B.. P. F. KI\G’;.~oN macrofauna

1976. The dynamics of estuarinc

proc~ssca. 1’01 I. edited by M. L. Wiley.

in the offshore

& M. StiI.ADER.

1974. Long-term

mud of the Northumberland

population

trends of the bcnthtc

coast. .I. )~NT. hirjl. As\

i’.K..

Vol. 54. pp

785 795. CA ro. 1.. 1977. Recent

sedimentological

marine areas in south-western

and gochemical

Sweden. St&e.

conditions

and pollution

problcmh

in t~\t~

I 158.

Vol. 6. pp.

I

C.alo. I.. I. Valen C4to.

och bottenfaumstiska un&rsDknmgar O~sso~ & R. ROSFUHEK<~. 1975. Sedimentologiska ett omrade att rcstaurerd. Giireho,a.c Narrrrhis/o~i,rX(? ;\ltcsrw~ :i,shd. pp. I3 -15.

I.. I. OLSWL 8; R. Rev

\RI KC;.1978. Sediments. mciofauna and macrofauna

Swedish with English bummary). HF~RIKSSOS. R.. 1968. The bottom HFNKtKsoh.

R..

in the .4xkimsvlk

iln

.S/arctr.s .Xarrrrr.. PM 1046. 90 pp.. (mimeo.).

1969. Influence

fauna in polluted areas of the Sound. 0iLo.s. Vol.

of pollution

on the hottom

fauna

of the Sound

19. pp. I I I I?,.

l&c’iundl.

Oil,<,..

in benthtc

macro-

Vol. 20. pp. CO?- 523. Jo~rhsot.

M.G

invertebrates

&

R.O.

BRISK&II 14.51. 1971. A$sociatlons

LAXDX~R. L.. K.

NILSSOS & R. Ros~>ab~(,.

benthic macrofauna

and

spcccles dtversity

J. Ftsh. Rrs. Ed Cm.. Vol. 28. pp. 168% 169;.

of Bay of Quintc and Lake Ontario.

1977. Assessment of industrial

pollution

by mean< (>!

surveys along the Swedish Baltic COBFI. Ctr//c,n IY77. pp. 324 3?9

LFPPAKOSKI. E.. 1968. Some effects of pollution

Helyoltindcr ~t~i.rs.i\~ee~c,sun,c,~.\.. \‘ol.

I 7. pp. 29

on the benthic

LWP~KOSKI. E.. 1975. Asscsamcnt of degrrc of pollution and brackish water enktronments. Lrr. U.. 1968. A quantitarivc

>itld\

of the Gullmarsfjord

on the basis of macrozoobenthos

.4(,/1/ Aco&mlNc~ Ahomris. of

environment

I 30I

henthic infauna

in mat-in?

Ser. B. Vol. 35(Z). pp 1 90

in Pueet Sound.

Fi.rkf)ir.

Hn~,L’m/w

.Skr. %I.

Vol. 14. pp. 229.556. Ltyr)aoTtI.

A.. 1935. Die .A.rx)ziaticmcn der manncn

MOI I\VDI-11.A. R.. 192X. Animal

communities

Wcichb6dcrt.

L’ppt.. Vol.

Zoo/. B&.

on soft bottom area,

in the Ciullmar

IS. pp. i?l

Fjord.

36s.

lirr.~r~&~~i :I

Zool. s/0 Ii+?? 1927. No. 1. 90 p[‘_ MOLA?DI:R. A.K.. 1962. Studiek on the fauna in the fjords of Bohuslln tribution of different associations. Ark. Zoo/. SW. -7.Vol. 15.pp. 1 -64. MO~I~~I~ORD.

M.D..

1962. An index of similarity

Pro,ura.c.sirt .COI/XO/O~J,, edited by P. W. Murphy, Nrtro~ ~1. K. G.. I. OI.SSOX & I_. A\‘tmCv.

and its application Butterworths.

1977. Quantitative

with refcrcnce

to classificator)

London.

to the di+

problems.

In

pp. 43. 50.

investigations

on the macro-

and mrio-

benthic fauna in the GGta River estuary. Zl,otr. Vol. 5. pp. I .C-18 OLSSO\.

1.. R. Rosc~er

KC, & E. &t-\r>tr.

Swedish estuaries. A&io.

Vol. 2. pp. I58

1977

Benthic

fauna

and rooplankton

in soms polluted

163.

Prn~\o~. T. H.. 1970. The henthic ecology of Loch Linnhe and Loch Eil. i\ sea-loch hystcm on rhz \test coabt of Scotland. I. The physical environment and distribution of the macrobenthic laun:t. J. “.y/I. ,,&I!.. Biol. .&Xl/.. Vol. 5. pp. I -34. PI ARSON.T. H. & R. ROWNHI.RG. 1976. A comparative

study of the effects on the marine cnvIronmcnt

of wastes from cellulose industries in Scotkdnd and Sweden. Amhio. Vol. 5, pp. 77 79 PI~AKSOX. T. H. Br R. Rosr \BIKG.

1978. Macrobenthic

succession in relation

IO organic

enrichment

and pollution of the marine environment. Oceanogr. Mar. Viol. Anti. Rev.. Vol. 16. pp. 23 31 1. PFTFRSFN. C.G. J.. 1913. Valuation of the sea. II. The animal communities of the sea bottom anti their importance for marine zoogeography. Rep. Dan. &of. SOY.No. 21. 44 pp. PFTFKSFU. C.G. J.. 1924. A brief survey of the animal communities in Danish waters. based upon quantitative

samples taken with the bortom sampler. .I~J. J. S(?.. Ser. 5. Vol. 7 (41). pp 343 354.

SALINITY-STRATIFIED

BENTHIC

FAUNA

203

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