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Southern Ocean deep-sea biodiversity—From patterns to processes
ARTICLE IN PRESS Deep-Sea Research II 56 (2009) 1732–1738
Contents lists available at ScienceDirect
Deep-Sea Research II journal homepage: www.elsevier.com/locate/dsr2
Southern Ocean deep-sea biodiversity—From patterns to processes Angelika Brandt a,, Brigitte Ebbe b a b
Zoological Institute and Zoological Museum, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany ¨nig, Adenauerallee 160, D53113 Bonn, Germany Forschungsinstitut Senckenberg, Abt. DZMB c/o Zoologisches Forschungsmuseum Alexander Ko
a r t i c l e in f o
a b s t r a c t
Available online 28 May 2009
The Southern Ocean is characterized by a narrow and deep shelf, an almost isothermal water column and a large area of deep sea surrounding Antarctica. However, knowledge of the deep-sea faunal composition, particularly in the Southern Ocean, is still scarce in comparison with shelf and upper slope environment. For that reason a deep-sea project was devoted to investigate this little-known area of the Southern Ocean. ANDEEP (ANtarctic benthic DEEP-sea biodiversity: colonisation history and recent community patterns) took place in 2002–2005 and provided first insights into the biodiversity and biogeography of Southern Ocean benthic animals from meio- to megafauna. The results with the very general patterns are outlined here. Based on the knowledge on biodiversity patterns gained through ANDEEP, a follow-up project, ANDEEP-SYSTCO (SYSTem COupling), was established in the international polar year in order to investigate the processes driving the biodiversity pattern observed. This expedition took place in 2007/2008 and only preliminary data can be presented at this stage given that the material was available for only a couple of months since the return of R.V. Polarstern. Some key results identified after the SYSTCO expedition are presented. & 2009 Elsevier Ltd. All rights reserved.
Keywords: Southern Ocean Biodiversity Benthos ANDEEP SYSTCO
1. Background When plans for a deep-sea expedition first came to life, few deep-sea biology studies had been carried out in the Southern Ocean (SO), and none had been devoted exclusively to the deep sea. Between 1950 and 1960 during Russian and US expeditions of the R.V.s Eltanin, Glacier, Akademik Kurchatov, and Akademik D. Mendeleiev, deep-sea samples had been taken occasionally, the focus of the expeditions being the shelf off the South Orkneys and South Sandwich Islands. The Beagle Channel was sampled in 1873–1876 (HMS Challenger), including several deep-sea stations, and later during IBMANT (Interactions between the Magellan Region and the Antarctic, R.V. Polarstern) in 1994 (Arntz and Rios, 1999). More recent programmes, such as EPOS (European Polarstern Studies) and EASIZ (Ecology of the Antarctic Sea Ice Zone), also included collection of deep-sea data from the slope but rarely from abyssal sites. Both programmes have provided a wealth of benthic data on species of all taxonomic groups and functional guilds of the high Antarctic Weddell Sea and the Antarctic Peninsula (Arntz et al., 1990; Arntz and Gutt, 1997; Arntz and Clarke, 2002; Arntz and Brey, 2003). Most information on the ecology of benthic deep-sea fauna in the Weddell Sea comes from
Corresponding author. Tel.: +49 40 42838 2278; fax: +49 40 42838 3937.
E-mail addresses: [email protected] (A. Brandt), [email protected] (B. Ebbe). 0967-0645/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr2.2009.05.017
few stations sampled during EASIZ II in 1998 (Arntz and Clarke, 2002; Brandt, 2001). Faunistic data from previous Russian deepsea expeditions were summarised by Malyutina (2004). Since the pioneering deep-sea investigations in the early 1960s of the last century (e.g., Sanders et al., 1965; Sanders and Hessler, 1969), attempts to describe and explain patterns of species diversity have become a major goal in deep-sea biological research. On regional (e.g., basin-wide) spatial scales, diversity is apparently influenced by environmental factors such as organic matter fluxes, bottom-water oxygen concentrations, current velocity, and sediment type (Levine et al., 2001). There is also evidence for the existence of patterns in biodiversity at larger (global) scales; in particular, an apparent decrease in species richness among a number of taxa from the equator towards the poles (Poore and Wilson, 1993; Rex et al. 1993, 1997; Culver and Buzas, 2000) has been noted. However, despite several such studies, the deep-sea floor remains the least studied even though it is the largest single benthic habitat (Clarke and Johnston, 2003). This is especially the case for the deep Southern Ocean. Reasons for these large gaps in our knowledge are often somewhat trivial. Deep-sea research is expensive, logistically challenging and time consuming. A significant increase in Southern Ocean deep-sea biodiversity research since the year 2000 was possible due to the funding of one of the most ambitious international and interdisciplinary projects ever, the Census of Marine Life.
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2. The documentation of biodiversity patterns 2.1. ANDEEP ANDEEP (ANtarctic DEEP-sea benthic biodiversity: colonisation history and recent community patterns) was a multidisciplinary international project that involved a two-leg expedition to the Weddell and Scotia Seas in 2002 and a third expedition (ANDEEP III) in 2005 to the Cape and Agulhas Basins, Weddell Sea, Bellingshausen Sea, and Drake Passage (Fig. 1). The expeditions yielded a total of 40 biological, sedimentological and geological stations in 2002 and 2005. The ANDEEP expeditions recovered a tremendous number of organisms of all size classes, making it possible for the first time to compare Southern Ocean deep-sea faunas to those collected elsewhere using similar sampling strategies and the same array of gear. Extensive systematic and ecological results of these three expeditions were published in two volumes of Deep-Sea Research (Brandt and Hilbig, 2004; Brandt and Ebbe, 2007), as well as in numerous additional papers yielding a total of more than 100 publications on results from the Southern Ocean deep sea. The project revealed high levels of novel biodiversity; for example, 674 isopods species of which 585 were new to science and 295 polychaete species of which 91 were unknown before. One recent publication (Strugnell et al., 2008) explains the distribution of deep sea octopus predator on these species through most of the oceans from a common Antarctic ancestor, matching molecular dates to the timing of geological and physical changes. Physically, the Southern Ocean has some unique environmental characteristics, such as a very deep continental shelf due to the weight of the ice cover, as well as an almost isothermal water column. The SO shelf, especially the Weddell and Ross Seas, is the source for much of the deep water in the World’s Oceans. While eurybathy has already been demonstrated for SO benthic taxa (Brey et al., 1996), these hydrographic characteristics suggest that SO deep-sea faunas around the Antarctic share elements with both the adjacent shelf communities and the deep-sea faunas in other oceans. Bathymetric and biogeographic trends varied between taxa and were thought to be related to the reproduction
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of the different taxa as well as their dispersal abilities. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. Taxa with good dispersal capabilities tended to have stronger links to other oceans, particularly the Atlantic (e.g., foraminiferans), while poor dispersers (e.g., isopods, ostracods, nematodes) show a higher degree of endemism and likely include many species currently known only from the SO (Brandt et al., 2007a–c). The SO deep-sea biodiversity patterns observed challenge the hypothesis of a depressed species richness in this area. The rich benthic material serves as a sound basis for further systematic, evolutionary and ecological research. In general terms, ANDEEP aimed to conduct the first comprehensive survey of megafaunal, macrofaunal, and meiofaunal deepwater communities in the Scotia and Weddell Seas. A simple, but crucial Census of the Marine Life question was to discover what lives in the deep Southern Ocean in the framework of the field project CeDAMar. As mentioned above, an astoundingly high number of species was discovered in this deep and remote environment (Brandt et al., 2007a, b). Based on this rich and diverse material, we were able to characterise faunal communities in terms of their composition and their relation to depth and region, latitude, and longitude. We also investigated the similarity of the Scotia and Weddell Sea fauna at taxonomic (morphological) and genetic (molecular) levels to the fauna of Atlantic basins, on the one hand, and Antarctic shelf on the other and described the variety of seafloor habitats (Howe et al., 2004, 2007; Thomson, 2004) in tectonically active and inactive regions and determined the influence of ‘habitat diversity’ on species and genetic diversity over a variety of spatial scales. Among other parameters, highly variable surface productivity levels were evident from differences in the amounts of phytodetritus that accumulated on the seafloor. 2.2. Distributional patterns Distributional patterns were described ranging in scale from regional to global and including bathymetric (downslope) changes. Kaiser et al. (2007) documented that varibility in
Fig. 1. Location of ANDEEP I–III and SYSTCO stations. For exact localities of ANDEEP I–III see Brandt et al. (2007a–c), for localities of SYSTCO stations see Table 1.
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abundance at lower spatial (local) scale is as high at large (regional) scales at all taxonomic levels studied. It is assumed that the apparent rarity of many taxa may reflect extreme patchiness rather than low abundance. The true abundance of rare species will be difficult to establish using the sampling methods used to date. In future, it will be necessary to investigate small-scale variability on the seemingly homogeneous deep-sea floor much more closely. The recent discovery of cryptic species suggests that our estimations of the biodiversity of some taxa might even be too low. According to Raupach et al. (2007) molecular investigations of phylogenetic patterns and genetic variability among eight populations of a single munnopsid species, Betamorpha fusiformis (Barnard, 1920), widely distributed deep-sea benthic organisms of a homogeneous phenotype can differentiate into genetically highly divergent populations. Cryptic speciation is indicated by the sympatry of some isopod genotypes (Bro¨keland and Raupach, in press; Raupach et al., 2004; Raupach et al., 2007). In contrast, there is very little genetic divergence between Arctic and Antarctic populations of the deep-sea foraminiferan Epistominella exigua (Brady, 1884) (Pawlowski et al., 2007a, b). Megafaunal communities (Linse et al., 2007) are consistent with the above-described observations of isopod diversity patterns (Kaiser et al., 2007). They also exhibited considerable patchiness and changes in community structure that could not be linked to either depth, area, sediment grain size or temperature. Abundances were generally several orders of magnitude lower than in other oceans and decreased significantly with increasing depth. Sponges showed a depth-related shift in species composition roughly at 2500 m (Janussen et al., 2004), the same depth reported earlier for faunal boundaries among nematodes (Vanhove et al., 2004) and polychaetes (Hilbig, 2004). High abundance and diversity of carnivorous sponges (Cladorhiszidae), and the first record of a calcareous sponge in the Antarctic deep sea, were among the most interesting results of the study of these organisms (Janussen and Tendal, 2007).
2.3. Life history strategies The importance of life history strategies and larval biology for species distributional patterns and geographical ranges became obvious (Pearse et al., 2009). Unfortunately, information about the reproductive biology of abyssal benthos is still scanty, although juveniles and ovigerous females were present in some taxa, for example, species of polychaetes (Blake and Narayanaswamy, 2004). Biological results from the Eltanin expeditions in the deep Atlantic and Pacific documented that a high percentage of the shelf fauna can also be found on the slopes and in the deep sea (Menzies et al., 1973). On the contrary, data from the ANDEEP campaigns with R.V. Polarstern in the Southern Ocean demonstrated a high percentage of the deep-sea fauna to be unknown. One of the model taxa are the Isopoda, as these are best investigated in most deep-sea areas sampled. For example, for the Munnopsidae, Malyutina and Brandt (2007) documented that this family has its centre of biodiversity in the Southern Ocean deep sea with 219 species being identified from 40 stations. The investigations of Bro¨keland and Raupach (in press) show that speciation is presently taking place at abyssal depths in the SO. For the meiofaunal protists Foraminifera, Pawlowski et al. (2007a, b) demonstrated that some species have penetrated from shallow water into the deep ocean and even across the Atlantic towards the north polar area. The isothermal water column in the Southern Ocean may be particularly important in facilitating the exchange of species between shallow water and deep water (Tyler et al., 2000).
In summary, ANDEEP increased our knowledge of the scale and patterns of species diversity in the deep SO and improved our understanding of the origins of the abyssal SO fauna, its degree of endemism as well as species’ bathymetric ranges.
3. The attempt to understand the processes driving observed biodiversity patterns 3.1. SYSTCO–from census to ecosystem functioning While the ANDEEP project has revealed patterns of biodiversity within different faunal groups and documented that these can vary significantly (Brandt et al., 2007a–c), we still know very little about the ecology and role of deep-sea fauna in trophodynamic coupling and nutrient cycling in oceanic ecosystems. To fill this knowledge gap, a successor to the ANDEEP project, ANDEEP-SYSTCO (SYSTem COupling), has been started in the Atlantic sector of the Southern Ocean within the framework of the International Polar Year (IPY) with a first expedition ANT XXIV-2 staged from board of R.V. Polarstern between 28.11.2008 and 4.2.2009. This new project will try to find answers for the questions posed from the biodiversity and biogeography patterns observed during the ANDEEP campaigns. ANDEEP-SYSTCO addresses the processes responsible for the strong differences in biodiversity within and between taxa as well as between areas. SYSTCO aims to investigate the functional biodiversity and ecology of dominant abyssal species and examine the trophic structure and functioning of abyssal communities of the Atlantic sector of Southern Ocean, focusing on the role of the key organisms, which frequently occur in the samples, including their general feeding biology. SYSTCO will help to understand the role of the Southern Ocean in global energy budgets, climate change, and the functioning of atmospheric, pelagic, and benthic systems of the Southern Ocean. The approach of exploring a new or almost untouched geographic frontier is being complemented by using a new frontier linking major scientific disciplines. SYSTCO involves a wide variety of scientists from different disciplines, such as planktology, benthology, physical oceanography, geology, sedimentology, and biogeochemistry for simultaneous study of a defined area to shed light on atmospheric–pelagic–benthic coupling processes. 3.2. SYSTCO objectives Important objectives in the different realms are as follows: Atmosphere: SYSTCO aims to unravel surface fluxes from satellite data that were obtained from the Alfred-WegenerInstitute for Polar and Marine Sciences. Water column and plankton: SYSTCO aims to understand the influence of atmospheric processes on processes in the water column, the influence of the biogeochemistry of the surface water on primary productivity, and to relate these to vertical changes in the plankton community to abyssal depths with time. Benthos: SYSTCO investigates the biology of key abyssal species, the influence on abyssal life of the quantity and quality of food sinking through the water column, feeding ecology and trophic relationships of abyssal animals. Seabed characteristics: SYSTCO studies the effects of topography, sedimentology and biogeochemistry of sediment and pore water on benthic life and microhabitat formation. The benthic fauna depends on deep carbon export from pelagic production and particle sedimentation. For that reason the project
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Table 1 EBS SYSTCO stations, depth, calculated trawling distance, start and end position. Station
Region
Depth (m)
Trawl. Dist. (m)
Long. (start)
Long. (end)
Lat. (start)
Lat. (end)
PS PS PS PS PS
SPF LS WS MR SPF
2996–3000 1736–2114 5337–5338 2147–2153 2986–3003
1875 1209 3159 1389 1905
0101.120 W 03121.50W 02158.35W 02152.68E 0100.210 W
0101.140 W 03121.40W 02158.74W 02153.01E 0100.040 W
52101.97S 70104.82S 62100.37S 64128.76S 52101.55S
52101.800 S 70104.65S 62100.42S 64128.68S 52101.570 S
71/13–16 71/17–11 71/33–16 71/39–17 71/85–08
Abbreviations: SPF ¼ South Polar Front; LS ¼ Lazarev Sea; WS ¼ Weddell Sea; MR ¼ Maud Rise; W ¼ West; E ¼ East; S ¼ South; N ¼ North.
Taxa per station
3500
Sponges Solenogastres Bivalvenschale
3000
Bivalvia Gastropoda
individuals
2500
Scaphopoda Ophiroidea
2000
Chaethognatha Nematoda Polychaeta
1500
Pantopoda Copepoda
1000
Ostracodenschale Ostracoda
500
Mysidacea Amphipoda
0
Cumacea
PS 71/13-16
PS 71/17-11
PS 71/39-17
Tanaidacea Isopoda
stations Fig. 2. Macrobenthic composition at three SYSTCO stations.
aims to revisit a station on the way back to Cape Town in order to perform repeated measurements at the same station for an estimate of seasonal and episodic variabilities of the particle flux. The area investigated during SYSTCO will provide a basis for future monitoring programmes, i.e., global change studies and could serve as a time-series area, which could be revisited in future. SYSTCO is an IPY lead project, and it is also integrated into SCAR-EBA, CAML (Census of the Antarctic Marine Life) and CeDAMar (Census of the Diversity of Abyssal Marine Life). Data transfer is managed through SCAR-MarBIN to OBIS. Samples are handled through the German Centre for Marine Biodiversity (DZMB) in Wilhelmshaven, Germany, a department of the Senckenberg Institute. Polarstern only returned to Bremerhaven at the end of May of 2007. Since then sorting and some first analyses were performed based on the SYSTCO material. Because of the limited time available for research, only an anecdotal overview is available at this stage.
3.3. First preliminary results of the biodiversity and ecology of peracarid crustaceans and polychaetes During this SYSTCO expedition, quantitative and qualitative samples were taken at five stations between 1736 and 5338 m in different water masses and environments with different topographical and sedimentary conditions. Two stations were incomplete. The first station we took on our way south from Cape Town was revisited 7 weeks later on our way back to Cape Town. This station at 521S was the only station revisited, contrary to our original intention to revisit two stations. Material was collected for studies of the biodiversity and ecology including feeding biology of peracarid crustaceans (with focus on the Isopoda), and polychaetes. Of the many samples taken with a variety of gear,
those obtained with an epibenthic sledge (EBS) are sorted and available for first analyses. These catches covered a trawled area of 9537 m2 (Bathmann, in press). In general, numbers of specimens/1000 m increase from stations 13 (South Polar Front) to 17 (Lazarev Sea) and 39 (Maud Rise) (Table 1; Fig. 2). Peracarid taxa comprised about 20% of the macrofauna of the first two stations, while at station 39 at Maud Rise these represented only a minor fraction of the sample, as most of the organisms belonged to the Bivalvia (55%) (Fig. 2). Most of the animals sampled with the EBS at Maud Rise are species with free swimming larvae, while very few are brooders, which have a reduced dispersal capability and therefore cannot easily reach an isolated seamount like Maud Rise. Unique oceanographic characteristics of seamounts, including the Taylor column, which causes localised entrainment of larvae, may be responsible for a very different community composition. Isopoda comprised 46% of all peracarid taxa sampled with the EBS at the three stations examined to date (Table 2), followed by Amphipoda (26%), Cumacea (12%), Tanaidacea (11%), and Mysidacea (5%). These differences in abundance are also documented in Figs. 3 and 4, demonstrating that Isopoda, Amphipoda, and Cumacea occur most frequently at station 17, the southernmost station at about 2100 m depth in the Lazarev Sea. Figs. 3 and 4 illustrate the differences of peracarid taxa per station and document that only at station 17 on the lower slope closer to the continent, Amphipoda are about as frequent as Isopoda. This is not astonishing, as this taxon thrives on the continental shelf. However, with increasing depth, Isopoda become more important and our samples confirm the general results of the ANDEEP project (Brandt et al., 2007a–c). During ANT XXIV-2 we collected data for over 540 isopod specimens belonging to 15 isopod families. The deep stations below 2000 m depth shown here yielded approximately 50 species in eight asellote families.
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Peracarid taxa / station (1000 m) 300
Individuals
250 200 PS_71/39-17 PS 71_17-11 PS 71_13-16
150 100 50 0 Amphipoda
Tanaidacea
Cumacea Taxa
Mysidacea
Isopoda
Fig. 3. Taxa of Peracarida distributed at three SYSTCO stations sorted (normalised to 1000 m hauls). Black: stations 13–16 in the South Polar Front; diagonal lines: stations 17–11 in the Lazarev Sea; white: stations 39-17 at Maud Rise.
Abundance of Peracarida per station (1000 m) 400 350
Isopoda Mysidacea
n/1000 m
300
Cumacea Tanaidacea
250
Amphipoda 200 150 100 50 0 PS 71_13-16
PS 71_17-11
PS_71/39-17
Stations Fig. 4. Peracarid taxa per station (normalised to 1000 m hauls).
With regard to isopod family composition, the Desmosomatidae were more important than Munnopsidae followed by Haploniscidae. During the recent ANDEEP expeditions Munnopsididae were the most frequent and speciose Isopoda sampled in the deep Southern Ocean (Malyutina and Brandt, 2007). Analyses of gut contents, investigations of the functional morphology of target species as well as biochemical analyses, have been started. The latter includes analyses of lipids and other biomarkers. For example, Euryope sp. is characterised by a total lipid content of approximately 3% of dry weight. Alcohols comprise about 11% of the total lipid (long-chained fatty acids: wax esters are used for long time storage). Gooday et al. found 18:1 (n-7), 20:1 (n-9), 22:1 (n-7, n-9) in SO foraminifers, lipids that we also documented for the gut contents of Eurycope sp. The species seems to be omnivorous, its diet consists of detritus, diatoms, and foraminiferans (Laura Wu¨rzberg, pers. comm.). Regarding polychaetes, 35 families were found at only four stations. Results from the same three stations as those analysed for peracarid crustaceans are presented here. At all three stations, Spionidae and Ampharetidae were the most abundant families (Fig. 5). At the Maud Rise Station (39-17), Spionidae made up nearly 42% of all polychaetes, followed by the Lumbrineridae and Glyceridae (9% and 8%, respectively). The abundance of these two
motile families may be indicative of a high nutrient input. At the South Polar Front (Stations 13–16), abundance was very low in December (i.e., before the arrival of the plankton bloom), as was the diversity on family level. Among the most abundant families were the Sabellidae (9%), which are suspension feeders, perhaps indicating low nutrient input and sedimentation rate. Cirratulidae were also abundant, contributing 6% to total polychaete abundance. In the Lazarev Sea (Stations 17–11), abundance was about eight times as high, and aside from the spionids and ampharetids, two burrowing families were quite abundant: Fauveliopsidae and Maldanidae, which contributed 14% and nearly 8%, respectively, of all individuals. Overall, the total polychaete abundance mirrors that of the peracarid crustaceans. The results of the feeding ecology and trophic structure of the macrofauna will later be compared and combined with the findings of research groups examining other aspects of the Southern Ocean foodweb. The comprehensive datasets on diversity and colonisation patterns available from ANDEEP I–III, together with the results from SYSTCO on foodweb dynamics, will lead to a better understanding of the trophodynamic role of deep-sea fauna in the ecology of the Atlantic sector of the Southern Ocean.
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1737
180 160
Lumbrineridae
140
Glyceridae Maldanidae
n/1000 m
120 100 80
Fauveliopsidae Sabellidae Cirratulidae Ampharetidae
60
Spionidae
40 20 0 13-16
17-11 Stations
39-17
Fig. 5. Abundance of selected polychaete families at three SYSTCO stations, normalised to 1000-m hauls.
3.4. Key results identified to date of the ANDEEP-SYSTCO project are: General
analyses of Eurycope sp. This is ANDEEP publication # 113. Within SCAR-EBA the paper also contributes to the Census of Marine Life Projects CeDAMar (Census of the Divesity of Abyssal Marine life) and CAML (Census of Antarctic Marine Life).
The Southern Polar Front (521S) is characterised by low
diversity and abundance in the macrofauna, even after a slight plankton bloom in spring (revisit of stations after 7 weeks). Eastern Weddell Sea and Lazarev Sea are generally poorer in species and abundance of organisms in the deep sea than the western Weddel Sea. Maud Rise (seamount) differs completely in taxon composition from the abyssal stations. Fauna
Discovery of the rare Monoplacophora Laevipilina Antarctica,
which will help to elucidate the phylogenetic position of this taxon. High numbers of Bivalvia at Maud Rise (52% of the macrofauna) possibly indicating high particle availability for filter feeders. Sampling of a large number of small calcareous Porifera and of a large carnivorous sponge (701S Lazarev Sea, 2100 m). Finding symbioses, parasitic gastropods on holothurians and crinoids, many parasitic copepods on a scale worm and on fishes. Sampling of more than 10 specimens of Haplomunnidae, a very rare deep-sea isopod family, at Maud Rise.
The expedition ANDEEP-SYSTCO has been a story of success and cooperation. It has been one of very few cruises run jointly by water column and seafloor specialists. Integration was achieved across nations, major disciplines, and projects. Due to unfavourable ice conditions only one station in the polar front could be revisited. We now intend to build on this study with a follow-up project to be applied for after the IPY.
Acknowledgements The crew of R.V. ‘‘Polarstern’’ is thanked for their help and logistic support during the expedition ANT XXIV/2 (SYSTCO), the AWI for logistics. Laura Wu¨rzberg is thanked for the first lipid
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Culver, S.J., Buzas, M.A., 2000. Global latitudinal species diversity gradient in deepsea benthic foraminifera. Deep-Sea Research I 47, 259–275. Hilbig, B., 2004. Polychaetes of the deep Weddell and Scotia Seas-composition and zoogeographical links. Deep-Sea Research II 51 (14–16), 1817–1827. Howe, J.A., Shimmield, T.M., Diaz, R., 2004. Deep-water sedimentary environments of the northwestern Weddell Sea and South Sandwich Islands, Antarctica. Deep-Sea Research II 51 (14–16), 1489–1515. Howe, J.A., Wilson, C.R., Shimmield, T.M., Diaz, R., Carpenter, L.W., 2007. Recent deep-water sedimentation, trace metal and radioisotopegeochemistry across the Southern Ocean and Northern Weddell Sea, Antarctica. Deep-Sea Research II 54, 1652–1681. Janussen, D., Tabachnick, K.R., Tendal, O.S., 2004. Deep-sea Hexactinellida (Porifera) of the Weddell Sea. Deep-Sea Research II 51, 1857–1883. Janussen, D., Tendal, O.S., 2007. Diversity and distribution of Porifera in the bathyal and abyssal Weddell Sea and adjacent areas. Deep-Sea Research II 54, 1864–1875. Kaiser, S., Barnes, D.K.A., Brandt, A., 2007. Slope and deep-sea abundance across scales: Southern Ocean isopods show how complex the deep sea can be. DeepSea Research II 54, 1776–1789. Linse, K., Brandt, A., Bohn, J., Danis, B., De Broyer, C., Heterier, V., Hilbig, B., Janussen, D., Lo´pez Gonza´lez, P.J., Schwabe, E., Thomson, M., 2007. Macro- and megabenthic communities in the abyssal Weddell Sea (South Atlantic). DeepSea Research II 54, 1848–1863. Levine, L.A., Etter, R.J., Rex, M.A., Gooday, A.J., Smith, C.R., Pineda, J., Stuart, C.T., Hessler, R.R., Pawson, D., 2001. Environmental influences on regional deep-sea species diversity. Annual Review of Ecology and Systematics 32, 51–93. Malyutina, M., Brandt, A., 2007. Diversity and zoogeography of Antarctic deep-sea Munnopsidae (Crustacea, Isopoda, Asellota). Deep-Sea Research II 54, 1790–1805. Malyutina, M., 2004. Russian deep-sea investigations of Antarctic fauna. Deep-Sea Research II 51, 1551–1570. Menzies, R.J., George, R.Y., Rowe, G.T., 1973. Abyssal Environment and Ecology of the World Oceans. Wiley, New York, London, Sydney, Toronto, pp. 1–488. Pawlowski, J., Fahrni, J., Lecroq, B., Longet, D., Cornelius, N., Excoffier, L., Cedhagen, T., Gooday, A.J., 2007a. Bipolar gene flow in deep-sea benthic foraminifera. Molecular Ecology 16, 4089–4096. Pawlowski, J., Bowser, S.S., Gooday, A., 2007b. A note on the genetic similarity between shallow- and deep-water Epistominella vitrea (Foraminifera) in the Antarctic. Deep-Sea Research II 54, 1720–1726.
Pearse, John S., Richard Mooi, Susanne J., Lockhart, Angelika Brandt, 2009. Brooding and Species Diversity in the Southern Ocean: Selection for Brooders or Speciation within Brooding Clades? In: Igor Krupnik, Michael A., Lang, Scott, E., Miller, (ed.), Smithsonian at the Poles: Contributions to International Polar Year Science. Proceedings of Smithsonian at the Poles Symposium, Smithsonian Institution, Washington, DC, 3–4 May 2007. Washington, DC: Smithsonian Institution Scholarly Press, pp. 181–196. Poore, G.C.B., Wilson, G.D.F., 1993. Marine species richness. Nature 361, 597–598. Raupach, M., Held, C., Wa¨gele, J.-W., 2004. Multiple colonization of the deep sea by the Asellota (Crustacea: Peracarida: Isopoda). Deep-Sea Research II 51 (14–16), 1787–1796. Raupach, M.J., Malyutina, M., Brandt, A., Wa¨gele, J.W., 2007. Molecular data reveal a highly diverse species flock within the deep-sea isopod Betamorpha fusiformis (Crustacea: Isopoda: Asellota) in the Southern Ocean. Deep-Sea Research II 54, 1820–1830. Rex, M.A., Etter, R.J., Stuart, C.T., 1997. Large-scale patterns of species diversity in the deep-sea benthos. In: Ormond, R.F.G., Gage, J.D., Angel, M.v. (Eds.), Marine Biodiversity: Patterns and Processes. Cambridge University Press, Cambridge, pp. 94–122. Rex, M.A., Stuart, C.T., Hessler, R.R., Allen, J.A., Sanders, H.L., Wilson, G.D.F., 1993. Global-scale latitudinal patterns of species diversity in the deep-sea benthos. Nature, London 365, 636–639. Sanders, H.L., Hessler, R.R., 1969. Ecology of the deep-sea benthos. Science 163, 1419–1424. Sanders, H.L., Hessler, R.R., Hampson, G.R., 1965. An introduction to the study of deep-sea benthic faunal assemblages along the Gay Head–Bermuda transect. Deep-Sea Research 1, 845–876. Strugnell, J.M., Rogers, A.D., Prodohl, P.A., Collins, P.A., Allcock, A.l., 2008. The thermohaline expressway: the Southern Ocean as a centre of origin for deepsea octopuses. Cladistics 24, 853–860. Thomson, M.R.A., 2004. Geological and palaeoenvironmental history of the Scotia Sea region as a basis for biological interpretation. Deep-Sea Research II 51, 1467–1487. Tyler, P.A., Young, C.M., Clarke, A., 2000. Temperature and pressure tolerances of embryos and larvae of the Antarctic sea urchin Sterechinus neumayeri (Echinodermata: Echinoidea): potential for deep-sea invasion from high latitudes. Marine Ecology Progress Series 192, 173–180. Vanhove, S., Vermeeren, H., Vanreusel, A., 2004. Meiofauna towards the South Sandwich Trench (750–6300 m), focus on nematodes. Deep-Sea Research II 51, 1665–1687.
Contents lists available at ScienceDirect
Deep-Sea Research II journal homepage: www.elsevier.com/locate/dsr2
Southern Ocean deep-sea biodiversity—From patterns to processes Angelika Brandt a,, Brigitte Ebbe b a b
Zoological Institute and Zoological Museum, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany ¨nig, Adenauerallee 160, D53113 Bonn, Germany Forschungsinstitut Senckenberg, Abt. DZMB c/o Zoologisches Forschungsmuseum Alexander Ko
a r t i c l e in f o
a b s t r a c t
Available online 28 May 2009
The Southern Ocean is characterized by a narrow and deep shelf, an almost isothermal water column and a large area of deep sea surrounding Antarctica. However, knowledge of the deep-sea faunal composition, particularly in the Southern Ocean, is still scarce in comparison with shelf and upper slope environment. For that reason a deep-sea project was devoted to investigate this little-known area of the Southern Ocean. ANDEEP (ANtarctic benthic DEEP-sea biodiversity: colonisation history and recent community patterns) took place in 2002–2005 and provided first insights into the biodiversity and biogeography of Southern Ocean benthic animals from meio- to megafauna. The results with the very general patterns are outlined here. Based on the knowledge on biodiversity patterns gained through ANDEEP, a follow-up project, ANDEEP-SYSTCO (SYSTem COupling), was established in the international polar year in order to investigate the processes driving the biodiversity pattern observed. This expedition took place in 2007/2008 and only preliminary data can be presented at this stage given that the material was available for only a couple of months since the return of R.V. Polarstern. Some key results identified after the SYSTCO expedition are presented. & 2009 Elsevier Ltd. All rights reserved.
Keywords: Southern Ocean Biodiversity Benthos ANDEEP SYSTCO
1. Background When plans for a deep-sea expedition first came to life, few deep-sea biology studies had been carried out in the Southern Ocean (SO), and none had been devoted exclusively to the deep sea. Between 1950 and 1960 during Russian and US expeditions of the R.V.s Eltanin, Glacier, Akademik Kurchatov, and Akademik D. Mendeleiev, deep-sea samples had been taken occasionally, the focus of the expeditions being the shelf off the South Orkneys and South Sandwich Islands. The Beagle Channel was sampled in 1873–1876 (HMS Challenger), including several deep-sea stations, and later during IBMANT (Interactions between the Magellan Region and the Antarctic, R.V. Polarstern) in 1994 (Arntz and Rios, 1999). More recent programmes, such as EPOS (European Polarstern Studies) and EASIZ (Ecology of the Antarctic Sea Ice Zone), also included collection of deep-sea data from the slope but rarely from abyssal sites. Both programmes have provided a wealth of benthic data on species of all taxonomic groups and functional guilds of the high Antarctic Weddell Sea and the Antarctic Peninsula (Arntz et al., 1990; Arntz and Gutt, 1997; Arntz and Clarke, 2002; Arntz and Brey, 2003). Most information on the ecology of benthic deep-sea fauna in the Weddell Sea comes from
Corresponding author. Tel.: +49 40 42838 2278; fax: +49 40 42838 3937.
E-mail addresses: [email protected] (A. Brandt), [email protected] (B. Ebbe). 0967-0645/$ - see front matter & 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr2.2009.05.017
few stations sampled during EASIZ II in 1998 (Arntz and Clarke, 2002; Brandt, 2001). Faunistic data from previous Russian deepsea expeditions were summarised by Malyutina (2004). Since the pioneering deep-sea investigations in the early 1960s of the last century (e.g., Sanders et al., 1965; Sanders and Hessler, 1969), attempts to describe and explain patterns of species diversity have become a major goal in deep-sea biological research. On regional (e.g., basin-wide) spatial scales, diversity is apparently influenced by environmental factors such as organic matter fluxes, bottom-water oxygen concentrations, current velocity, and sediment type (Levine et al., 2001). There is also evidence for the existence of patterns in biodiversity at larger (global) scales; in particular, an apparent decrease in species richness among a number of taxa from the equator towards the poles (Poore and Wilson, 1993; Rex et al. 1993, 1997; Culver and Buzas, 2000) has been noted. However, despite several such studies, the deep-sea floor remains the least studied even though it is the largest single benthic habitat (Clarke and Johnston, 2003). This is especially the case for the deep Southern Ocean. Reasons for these large gaps in our knowledge are often somewhat trivial. Deep-sea research is expensive, logistically challenging and time consuming. A significant increase in Southern Ocean deep-sea biodiversity research since the year 2000 was possible due to the funding of one of the most ambitious international and interdisciplinary projects ever, the Census of Marine Life.
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2. The documentation of biodiversity patterns 2.1. ANDEEP ANDEEP (ANtarctic DEEP-sea benthic biodiversity: colonisation history and recent community patterns) was a multidisciplinary international project that involved a two-leg expedition to the Weddell and Scotia Seas in 2002 and a third expedition (ANDEEP III) in 2005 to the Cape and Agulhas Basins, Weddell Sea, Bellingshausen Sea, and Drake Passage (Fig. 1). The expeditions yielded a total of 40 biological, sedimentological and geological stations in 2002 and 2005. The ANDEEP expeditions recovered a tremendous number of organisms of all size classes, making it possible for the first time to compare Southern Ocean deep-sea faunas to those collected elsewhere using similar sampling strategies and the same array of gear. Extensive systematic and ecological results of these three expeditions were published in two volumes of Deep-Sea Research (Brandt and Hilbig, 2004; Brandt and Ebbe, 2007), as well as in numerous additional papers yielding a total of more than 100 publications on results from the Southern Ocean deep sea. The project revealed high levels of novel biodiversity; for example, 674 isopods species of which 585 were new to science and 295 polychaete species of which 91 were unknown before. One recent publication (Strugnell et al., 2008) explains the distribution of deep sea octopus predator on these species through most of the oceans from a common Antarctic ancestor, matching molecular dates to the timing of geological and physical changes. Physically, the Southern Ocean has some unique environmental characteristics, such as a very deep continental shelf due to the weight of the ice cover, as well as an almost isothermal water column. The SO shelf, especially the Weddell and Ross Seas, is the source for much of the deep water in the World’s Oceans. While eurybathy has already been demonstrated for SO benthic taxa (Brey et al., 1996), these hydrographic characteristics suggest that SO deep-sea faunas around the Antarctic share elements with both the adjacent shelf communities and the deep-sea faunas in other oceans. Bathymetric and biogeographic trends varied between taxa and were thought to be related to the reproduction
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of the different taxa as well as their dispersal abilities. In groups such as the isopods and polychaetes, slope assemblages included species that have invaded from the shelf. Taxa with good dispersal capabilities tended to have stronger links to other oceans, particularly the Atlantic (e.g., foraminiferans), while poor dispersers (e.g., isopods, ostracods, nematodes) show a higher degree of endemism and likely include many species currently known only from the SO (Brandt et al., 2007a–c). The SO deep-sea biodiversity patterns observed challenge the hypothesis of a depressed species richness in this area. The rich benthic material serves as a sound basis for further systematic, evolutionary and ecological research. In general terms, ANDEEP aimed to conduct the first comprehensive survey of megafaunal, macrofaunal, and meiofaunal deepwater communities in the Scotia and Weddell Seas. A simple, but crucial Census of the Marine Life question was to discover what lives in the deep Southern Ocean in the framework of the field project CeDAMar. As mentioned above, an astoundingly high number of species was discovered in this deep and remote environment (Brandt et al., 2007a, b). Based on this rich and diverse material, we were able to characterise faunal communities in terms of their composition and their relation to depth and region, latitude, and longitude. We also investigated the similarity of the Scotia and Weddell Sea fauna at taxonomic (morphological) and genetic (molecular) levels to the fauna of Atlantic basins, on the one hand, and Antarctic shelf on the other and described the variety of seafloor habitats (Howe et al., 2004, 2007; Thomson, 2004) in tectonically active and inactive regions and determined the influence of ‘habitat diversity’ on species and genetic diversity over a variety of spatial scales. Among other parameters, highly variable surface productivity levels were evident from differences in the amounts of phytodetritus that accumulated on the seafloor. 2.2. Distributional patterns Distributional patterns were described ranging in scale from regional to global and including bathymetric (downslope) changes. Kaiser et al. (2007) documented that varibility in
Fig. 1. Location of ANDEEP I–III and SYSTCO stations. For exact localities of ANDEEP I–III see Brandt et al. (2007a–c), for localities of SYSTCO stations see Table 1.
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abundance at lower spatial (local) scale is as high at large (regional) scales at all taxonomic levels studied. It is assumed that the apparent rarity of many taxa may reflect extreme patchiness rather than low abundance. The true abundance of rare species will be difficult to establish using the sampling methods used to date. In future, it will be necessary to investigate small-scale variability on the seemingly homogeneous deep-sea floor much more closely. The recent discovery of cryptic species suggests that our estimations of the biodiversity of some taxa might even be too low. According to Raupach et al. (2007) molecular investigations of phylogenetic patterns and genetic variability among eight populations of a single munnopsid species, Betamorpha fusiformis (Barnard, 1920), widely distributed deep-sea benthic organisms of a homogeneous phenotype can differentiate into genetically highly divergent populations. Cryptic speciation is indicated by the sympatry of some isopod genotypes (Bro¨keland and Raupach, in press; Raupach et al., 2004; Raupach et al., 2007). In contrast, there is very little genetic divergence between Arctic and Antarctic populations of the deep-sea foraminiferan Epistominella exigua (Brady, 1884) (Pawlowski et al., 2007a, b). Megafaunal communities (Linse et al., 2007) are consistent with the above-described observations of isopod diversity patterns (Kaiser et al., 2007). They also exhibited considerable patchiness and changes in community structure that could not be linked to either depth, area, sediment grain size or temperature. Abundances were generally several orders of magnitude lower than in other oceans and decreased significantly with increasing depth. Sponges showed a depth-related shift in species composition roughly at 2500 m (Janussen et al., 2004), the same depth reported earlier for faunal boundaries among nematodes (Vanhove et al., 2004) and polychaetes (Hilbig, 2004). High abundance and diversity of carnivorous sponges (Cladorhiszidae), and the first record of a calcareous sponge in the Antarctic deep sea, were among the most interesting results of the study of these organisms (Janussen and Tendal, 2007).
2.3. Life history strategies The importance of life history strategies and larval biology for species distributional patterns and geographical ranges became obvious (Pearse et al., 2009). Unfortunately, information about the reproductive biology of abyssal benthos is still scanty, although juveniles and ovigerous females were present in some taxa, for example, species of polychaetes (Blake and Narayanaswamy, 2004). Biological results from the Eltanin expeditions in the deep Atlantic and Pacific documented that a high percentage of the shelf fauna can also be found on the slopes and in the deep sea (Menzies et al., 1973). On the contrary, data from the ANDEEP campaigns with R.V. Polarstern in the Southern Ocean demonstrated a high percentage of the deep-sea fauna to be unknown. One of the model taxa are the Isopoda, as these are best investigated in most deep-sea areas sampled. For example, for the Munnopsidae, Malyutina and Brandt (2007) documented that this family has its centre of biodiversity in the Southern Ocean deep sea with 219 species being identified from 40 stations. The investigations of Bro¨keland and Raupach (in press) show that speciation is presently taking place at abyssal depths in the SO. For the meiofaunal protists Foraminifera, Pawlowski et al. (2007a, b) demonstrated that some species have penetrated from shallow water into the deep ocean and even across the Atlantic towards the north polar area. The isothermal water column in the Southern Ocean may be particularly important in facilitating the exchange of species between shallow water and deep water (Tyler et al., 2000).
In summary, ANDEEP increased our knowledge of the scale and patterns of species diversity in the deep SO and improved our understanding of the origins of the abyssal SO fauna, its degree of endemism as well as species’ bathymetric ranges.
3. The attempt to understand the processes driving observed biodiversity patterns 3.1. SYSTCO–from census to ecosystem functioning While the ANDEEP project has revealed patterns of biodiversity within different faunal groups and documented that these can vary significantly (Brandt et al., 2007a–c), we still know very little about the ecology and role of deep-sea fauna in trophodynamic coupling and nutrient cycling in oceanic ecosystems. To fill this knowledge gap, a successor to the ANDEEP project, ANDEEP-SYSTCO (SYSTem COupling), has been started in the Atlantic sector of the Southern Ocean within the framework of the International Polar Year (IPY) with a first expedition ANT XXIV-2 staged from board of R.V. Polarstern between 28.11.2008 and 4.2.2009. This new project will try to find answers for the questions posed from the biodiversity and biogeography patterns observed during the ANDEEP campaigns. ANDEEP-SYSTCO addresses the processes responsible for the strong differences in biodiversity within and between taxa as well as between areas. SYSTCO aims to investigate the functional biodiversity and ecology of dominant abyssal species and examine the trophic structure and functioning of abyssal communities of the Atlantic sector of Southern Ocean, focusing on the role of the key organisms, which frequently occur in the samples, including their general feeding biology. SYSTCO will help to understand the role of the Southern Ocean in global energy budgets, climate change, and the functioning of atmospheric, pelagic, and benthic systems of the Southern Ocean. The approach of exploring a new or almost untouched geographic frontier is being complemented by using a new frontier linking major scientific disciplines. SYSTCO involves a wide variety of scientists from different disciplines, such as planktology, benthology, physical oceanography, geology, sedimentology, and biogeochemistry for simultaneous study of a defined area to shed light on atmospheric–pelagic–benthic coupling processes. 3.2. SYSTCO objectives Important objectives in the different realms are as follows: Atmosphere: SYSTCO aims to unravel surface fluxes from satellite data that were obtained from the Alfred-WegenerInstitute for Polar and Marine Sciences. Water column and plankton: SYSTCO aims to understand the influence of atmospheric processes on processes in the water column, the influence of the biogeochemistry of the surface water on primary productivity, and to relate these to vertical changes in the plankton community to abyssal depths with time. Benthos: SYSTCO investigates the biology of key abyssal species, the influence on abyssal life of the quantity and quality of food sinking through the water column, feeding ecology and trophic relationships of abyssal animals. Seabed characteristics: SYSTCO studies the effects of topography, sedimentology and biogeochemistry of sediment and pore water on benthic life and microhabitat formation. The benthic fauna depends on deep carbon export from pelagic production and particle sedimentation. For that reason the project
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Table 1 EBS SYSTCO stations, depth, calculated trawling distance, start and end position. Station
Region
Depth (m)
Trawl. Dist. (m)
Long. (start)
Long. (end)
Lat. (start)
Lat. (end)
PS PS PS PS PS
SPF LS WS MR SPF
2996–3000 1736–2114 5337–5338 2147–2153 2986–3003
1875 1209 3159 1389 1905
0101.120 W 03121.50W 02158.35W 02152.68E 0100.210 W
0101.140 W 03121.40W 02158.74W 02153.01E 0100.040 W
52101.97S 70104.82S 62100.37S 64128.76S 52101.55S
52101.800 S 70104.65S 62100.42S 64128.68S 52101.570 S
71/13–16 71/17–11 71/33–16 71/39–17 71/85–08
Abbreviations: SPF ¼ South Polar Front; LS ¼ Lazarev Sea; WS ¼ Weddell Sea; MR ¼ Maud Rise; W ¼ West; E ¼ East; S ¼ South; N ¼ North.
Taxa per station
3500
Sponges Solenogastres Bivalvenschale
3000
Bivalvia Gastropoda
individuals
2500
Scaphopoda Ophiroidea
2000
Chaethognatha Nematoda Polychaeta
1500
Pantopoda Copepoda
1000
Ostracodenschale Ostracoda
500
Mysidacea Amphipoda
0
Cumacea
PS 71/13-16
PS 71/17-11
PS 71/39-17
Tanaidacea Isopoda
stations Fig. 2. Macrobenthic composition at three SYSTCO stations.
aims to revisit a station on the way back to Cape Town in order to perform repeated measurements at the same station for an estimate of seasonal and episodic variabilities of the particle flux. The area investigated during SYSTCO will provide a basis for future monitoring programmes, i.e., global change studies and could serve as a time-series area, which could be revisited in future. SYSTCO is an IPY lead project, and it is also integrated into SCAR-EBA, CAML (Census of the Antarctic Marine Life) and CeDAMar (Census of the Diversity of Abyssal Marine Life). Data transfer is managed through SCAR-MarBIN to OBIS. Samples are handled through the German Centre for Marine Biodiversity (DZMB) in Wilhelmshaven, Germany, a department of the Senckenberg Institute. Polarstern only returned to Bremerhaven at the end of May of 2007. Since then sorting and some first analyses were performed based on the SYSTCO material. Because of the limited time available for research, only an anecdotal overview is available at this stage.
3.3. First preliminary results of the biodiversity and ecology of peracarid crustaceans and polychaetes During this SYSTCO expedition, quantitative and qualitative samples were taken at five stations between 1736 and 5338 m in different water masses and environments with different topographical and sedimentary conditions. Two stations were incomplete. The first station we took on our way south from Cape Town was revisited 7 weeks later on our way back to Cape Town. This station at 521S was the only station revisited, contrary to our original intention to revisit two stations. Material was collected for studies of the biodiversity and ecology including feeding biology of peracarid crustaceans (with focus on the Isopoda), and polychaetes. Of the many samples taken with a variety of gear,
those obtained with an epibenthic sledge (EBS) are sorted and available for first analyses. These catches covered a trawled area of 9537 m2 (Bathmann, in press). In general, numbers of specimens/1000 m increase from stations 13 (South Polar Front) to 17 (Lazarev Sea) and 39 (Maud Rise) (Table 1; Fig. 2). Peracarid taxa comprised about 20% of the macrofauna of the first two stations, while at station 39 at Maud Rise these represented only a minor fraction of the sample, as most of the organisms belonged to the Bivalvia (55%) (Fig. 2). Most of the animals sampled with the EBS at Maud Rise are species with free swimming larvae, while very few are brooders, which have a reduced dispersal capability and therefore cannot easily reach an isolated seamount like Maud Rise. Unique oceanographic characteristics of seamounts, including the Taylor column, which causes localised entrainment of larvae, may be responsible for a very different community composition. Isopoda comprised 46% of all peracarid taxa sampled with the EBS at the three stations examined to date (Table 2), followed by Amphipoda (26%), Cumacea (12%), Tanaidacea (11%), and Mysidacea (5%). These differences in abundance are also documented in Figs. 3 and 4, demonstrating that Isopoda, Amphipoda, and Cumacea occur most frequently at station 17, the southernmost station at about 2100 m depth in the Lazarev Sea. Figs. 3 and 4 illustrate the differences of peracarid taxa per station and document that only at station 17 on the lower slope closer to the continent, Amphipoda are about as frequent as Isopoda. This is not astonishing, as this taxon thrives on the continental shelf. However, with increasing depth, Isopoda become more important and our samples confirm the general results of the ANDEEP project (Brandt et al., 2007a–c). During ANT XXIV-2 we collected data for over 540 isopod specimens belonging to 15 isopod families. The deep stations below 2000 m depth shown here yielded approximately 50 species in eight asellote families.
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Peracarid taxa / station (1000 m) 300
Individuals
250 200 PS_71/39-17 PS 71_17-11 PS 71_13-16
150 100 50 0 Amphipoda
Tanaidacea
Cumacea Taxa
Mysidacea
Isopoda
Fig. 3. Taxa of Peracarida distributed at three SYSTCO stations sorted (normalised to 1000 m hauls). Black: stations 13–16 in the South Polar Front; diagonal lines: stations 17–11 in the Lazarev Sea; white: stations 39-17 at Maud Rise.
Abundance of Peracarida per station (1000 m) 400 350
Isopoda Mysidacea
n/1000 m
300
Cumacea Tanaidacea
250
Amphipoda 200 150 100 50 0 PS 71_13-16
PS 71_17-11
PS_71/39-17
Stations Fig. 4. Peracarid taxa per station (normalised to 1000 m hauls).
With regard to isopod family composition, the Desmosomatidae were more important than Munnopsidae followed by Haploniscidae. During the recent ANDEEP expeditions Munnopsididae were the most frequent and speciose Isopoda sampled in the deep Southern Ocean (Malyutina and Brandt, 2007). Analyses of gut contents, investigations of the functional morphology of target species as well as biochemical analyses, have been started. The latter includes analyses of lipids and other biomarkers. For example, Euryope sp. is characterised by a total lipid content of approximately 3% of dry weight. Alcohols comprise about 11% of the total lipid (long-chained fatty acids: wax esters are used for long time storage). Gooday et al. found 18:1 (n-7), 20:1 (n-9), 22:1 (n-7, n-9) in SO foraminifers, lipids that we also documented for the gut contents of Eurycope sp. The species seems to be omnivorous, its diet consists of detritus, diatoms, and foraminiferans (Laura Wu¨rzberg, pers. comm.). Regarding polychaetes, 35 families were found at only four stations. Results from the same three stations as those analysed for peracarid crustaceans are presented here. At all three stations, Spionidae and Ampharetidae were the most abundant families (Fig. 5). At the Maud Rise Station (39-17), Spionidae made up nearly 42% of all polychaetes, followed by the Lumbrineridae and Glyceridae (9% and 8%, respectively). The abundance of these two
motile families may be indicative of a high nutrient input. At the South Polar Front (Stations 13–16), abundance was very low in December (i.e., before the arrival of the plankton bloom), as was the diversity on family level. Among the most abundant families were the Sabellidae (9%), which are suspension feeders, perhaps indicating low nutrient input and sedimentation rate. Cirratulidae were also abundant, contributing 6% to total polychaete abundance. In the Lazarev Sea (Stations 17–11), abundance was about eight times as high, and aside from the spionids and ampharetids, two burrowing families were quite abundant: Fauveliopsidae and Maldanidae, which contributed 14% and nearly 8%, respectively, of all individuals. Overall, the total polychaete abundance mirrors that of the peracarid crustaceans. The results of the feeding ecology and trophic structure of the macrofauna will later be compared and combined with the findings of research groups examining other aspects of the Southern Ocean foodweb. The comprehensive datasets on diversity and colonisation patterns available from ANDEEP I–III, together with the results from SYSTCO on foodweb dynamics, will lead to a better understanding of the trophodynamic role of deep-sea fauna in the ecology of the Atlantic sector of the Southern Ocean.
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180 160
Lumbrineridae
140
Glyceridae Maldanidae
n/1000 m
120 100 80
Fauveliopsidae Sabellidae Cirratulidae Ampharetidae
60
Spionidae
40 20 0 13-16
17-11 Stations
39-17
Fig. 5. Abundance of selected polychaete families at three SYSTCO stations, normalised to 1000-m hauls.
3.4. Key results identified to date of the ANDEEP-SYSTCO project are: General
analyses of Eurycope sp. This is ANDEEP publication # 113. Within SCAR-EBA the paper also contributes to the Census of Marine Life Projects CeDAMar (Census of the Divesity of Abyssal Marine life) and CAML (Census of Antarctic Marine Life).
The Southern Polar Front (521S) is characterised by low
diversity and abundance in the macrofauna, even after a slight plankton bloom in spring (revisit of stations after 7 weeks). Eastern Weddell Sea and Lazarev Sea are generally poorer in species and abundance of organisms in the deep sea than the western Weddel Sea. Maud Rise (seamount) differs completely in taxon composition from the abyssal stations. Fauna
Discovery of the rare Monoplacophora Laevipilina Antarctica,
which will help to elucidate the phylogenetic position of this taxon. High numbers of Bivalvia at Maud Rise (52% of the macrofauna) possibly indicating high particle availability for filter feeders. Sampling of a large number of small calcareous Porifera and of a large carnivorous sponge (701S Lazarev Sea, 2100 m). Finding symbioses, parasitic gastropods on holothurians and crinoids, many parasitic copepods on a scale worm and on fishes. Sampling of more than 10 specimens of Haplomunnidae, a very rare deep-sea isopod family, at Maud Rise.
The expedition ANDEEP-SYSTCO has been a story of success and cooperation. It has been one of very few cruises run jointly by water column and seafloor specialists. Integration was achieved across nations, major disciplines, and projects. Due to unfavourable ice conditions only one station in the polar front could be revisited. We now intend to build on this study with a follow-up project to be applied for after the IPY.
Acknowledgements The crew of R.V. ‘‘Polarstern’’ is thanked for their help and logistic support during the expedition ANT XXIV/2 (SYSTCO), the AWI for logistics. Laura Wu¨rzberg is thanked for the first lipid
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