In: Pesquisa Antartica Brasileira (Brazilian Antarctic Research) 1(1) :1-10.

Macrozooplankton Communities from Weddell Sea Surface Waters, Antarctica

UWE PIATKOWSKI*

Alfred-Wegner-Institut für Polar- und Meeresforschung, D-2850 Bremerhaven, F .R. Gerrnany

INTRODUCTION Geographical distribution and relative In the southem and central Weddell Sea abundance of the euphausiid species are plankton sampling is possible only during the shown according to their importance in most summer season (December - March), when parts of the Southem Ocean parts of the sea ice melt and ice free polynyas Furthermore, hydrographic data and occur along the shelf-ice edge. In cantrast to duster analyses were applied to reveal faunal the waters off the Antarctic Peninsula, dissimilarities in different regions of the information on distribution and abundance of Weddell Sea. macrozooplankton from the Weddell Sea is very sparce, due to its difficult accessibility. MATERIAL AND METHODS Only a few distribution studies have During her frrst Antarctic cruise in been published so far, which concentrated on austral summer 1982/83 RV "Polarstern" euphausiids (Fevolden 1979, 1980; Siegel carried out a zooplankton sampling 1982) and chaetognaths (Bqllmann 1934). programme in various parts of the Weddell Hempel et al. (1983) repbrted on the Sea. Two sequences of stations were made in ice geographical distribution of euphausiids, free waters, one in the summer polynya along hyperiid amphipods and fish larvat:::, and the shelf-ice edge from Atka Bay (8°W) to recently several investigations were made on Gould Bay (43°W); the other across the the early life stages of the Antarctic Silverfish Weddell Sea partly along the marginal pack Pleuragramma antarcticum emphasizing its ice zone, ranging from Cape Norvegia (17°W) key position in the cold water ecosystem of to the ;orthwestem part of the Weddell Sea the Weddell Sea shelf (Keller 1983; Hubold, (51°W). Hempel (1983) reports on the cruise 1984, 1985). track and Drescher et al. (1983) give a In austral summer 1982/83 a compilation of the biological stations. zooplankton sampling programe was The standard zooplankton net was a undertaken in various parts of the Weddell Sea multiple Reetangular Midwater Trawl (RMT in order to extend our knowledge of the 1 +8m) described in detail by Roe and Shale zooplankton distribution in this region. (1979). The net consisted of three pairs of The present study provides a list of 0.32mm (RMT 1) and 4.5mm (RMT 8) mesh macrozooplankton taxa, of which several are 2 2 nets with net openings of 1m and 8m , described for the frrst time from this region. respectively. Altogether 30 RMT standard hauls were *Present address: Institut für Meereskunde der carried out ( Fig. I) as stratified oblique tows Universität Kiel, Abteilung Fischereibiologie, with maximum haul depths of approximately Düsjembrooker Weg 20, D-2300 Kiel), F.R. Gerrnany. 300m. ' Pesq. antart. bras., 1 (1), 1989 2 UWE PIATKOWSKI

•236 •232 •230 RV Polarslern "228 ANT 112 1983 RMT standard hauls

76° s

Fig. 1 - Map of investigation area and positions of sampling stations.

SW, Gould Bay Atka Bay,NE

:i) 100 150 200 2:il 300 3:il 400 500 Southern Shelf 600 700 Halley Bay 800 soo Trench 1000 1:ilü 2000 Filchner Depression a [ml

Fig. 2 - Water temperatures a~d bottom topography along 50 n'fffr~~~~~~~~~ the station sequences. (a) Transect from Gould Bay to Atka 100 Bay. (b) Transect from Cape Norvegia to the western 150 Weddell Sea. 200 2:il 300 Immediately after each haul the samples 500 were preserved in 4% borax buffered seawater 1000 formaldehyde solution. 1500 In this paper only data from RMT 8 2000 2500 samples are considered. They were sorted into 3000 the different taxa listed in Table I. The 3500 remaining smaller zooplankton, like copepods, 4000 ostracods and euphausiid larvae 4soo5000 L_ _::::=::~~~~~:__-~~ (mesozooplankton), was not sorted and kept as [mJ residual sample. Distribution pattems of

Pesq. antart. bras., 1 (1), 1989 MACROZOOPLANKTON COMMUNITIES FROM WEDDELL SURFACE WATERS 3

TABLE I Macrozooplankton and Nekton Taxa ldentified from Weddell Sea RMT 8 Sampies (mesh size 4.5mm) in February 1983. All Hauls Considered were Oblique Tows (300·0 m). + The Values of 3 the Relative Abundance (ind./1000m ) Represent an Average for the Total of Stations, at which the Taxon was Present. 3 For Occurrence in Different C:Jmmunities: + + avery abundant(> 10 ind./1000 m ). + common, ( +) only sporadically found,- absent. Taxon Occurrence Relative Abundance Occurrence in % (ind,/1 000 m3) community Maximum Mean+ A B c Coelenterata Pandeambra 3.3 0.1 0.1 + - - Calycopsis borchgrevinki 43.3 1 0.3 + + (+) Botrynema sp. 43.3 2 0.8 + (+) - Solmundella bitentaculata 6.7 0.1 <0.1 + - - Trachymedusae indet. 70.0 1 0.3 + + + Diphyes antarctica 100.0 20 6 ++ + + Dimophyes arctica 100.0 17 6 ++ + ++ Pyrostephos vanhoeffeni 80.0 18 3 + ++ + Vogtia serrata 26.7 7 3 + - - Periphy/la periphylla 6.7

TABLE I (Continuation) Macrozooplankton and Nekton Taxa Identified from Weddell Sea RMT 8 Sampies (mesh sh,e 4.5 mm) in February 1983. All Hauls Considered were Oblique Tows (300-0 m). + The Values of the .Relative Abundance (ind./100ft3) Represent an Average for the Total of Stations, at which the Taxon was Present. 3 For Occurrence in Different Communities: + + Very Abundant(> 10 ind./1000 m ), + common, ( +) only sporadically found,- absent. Taxon Occurrence Relative Abundance Occurrence in 3 % (indJ1000 m ) community Maximum Mean+ A 8 c Decapoda Larvae Notocrangon antarcticus 76.7 3 0.9 (+) + + Chorismus antarcticus 36.7 0.5 0.2 (+) + + Hymenodora gracüis 10.0 0.1 <0.1 + - - Acanthephyra pelagica 26.7 0.5 0.2 + - - Chaetognatha Eukrolmia hamata 100.0 34 7 ++ ++ + Eukrolmia bathypelagica 33.3 0.4 0.2 + + - Sagitta gazellae 100.0 16 6 ++ ++ ++ Sagitta man1 43.3 3 0.8 + + - Sagitta ma.xima 6.7 <0.1 <0.1 - + - Tunicata Salpa Thompsoni 60.0 385 23 ++ + + Pisces Larvae Pleuragramma antarcticum 80.0 14 2 + + ++ Aetlwtaxis mitopteryx 23.3 14 3 - + ++ Nofo-fheni i

Fig. 3 - Geographkai distribution and relative abundance of euphausiid species encountered, calculated from RMT 8 samples ~ in surface waters (~300m). (a) Euphausia superba. (b) Euphausia crystallorophias. (c) Thysanoessa macrura. Pesq. antart. bras., 1(1), 1989 MACROZOOPLANKTON COMMUNITIES FROM WEDDELL SURFACE WATERS 5

0 66° a e RV Polarslern 68" ANT 112 1983 •

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RV Polarslern ANT 1/2 1983

66° c RV Polarslern 68° ANT 112 1983

Pesq. antart. bras., 1(1), 1989 6 UWE PIATKOWSKI

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40 .._>. I ] .E ·v; 20 .._ c QJ ~ b & Dendragram af. duster analysis results far similarity camparisans between Weddell Sea samples Jaccard index ( overoge linkoge I F:ig. 4 - (a) Sampling stations related to macrozooplankton communities which were revealed by cluster analysis. (b) Dendrogram of cluster analysis for similarity comparisions between Weddell Sea samples. produced (Carmack and Poster 1975). The Iee (-1.8°C). Above the latter there is a warmer Shelf Water can be followed northward up to summer layer with temperatures up to -0.5°C. Atka Bay (Northem Shelf), where its The water masses beneath 1500m depth are temperature has risen to -1.8°C. In the Antarctic Bottom Water (ABW, ~ .0.0°C). northeastem parts a warmer summer layer A total of 70 macrozooplankton taxa was ( ""-1.4°C) covers the cold shelf water. The found, of which 55 were identified to species temperature profile along the section across level, ten to genus level, and five remained as the Weddell Sea indicates Warm Deep family (Table I). Frequency of occurrence as Water (WDW,"" 0.1°C) below 250m co­ weil as maximum and mean relative vered by a layer of cold winter water abundance of each taxon are present. Only Pesq. antart. bras., 1(1), 1989 MACROZOOPLANKTON COMMUNITIES FROM WEDDELL SURFACE WATERS 7

0 0 0 RV Polarstern 0 68° ANT 1/2 1983

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Fig. 5 - Geographical distribution and relative abundance calculated from RMT 8 samples in surface waters (~300m). (a) Eusirus propeperdentatus and (b) Sagitta marri. four species occurred in every sample: the southwest of Cape Norvegia (Station No. siphonophores Diphyes antarctica and 215). Maximum abundances of more than 100 Dimophyes arctica and the chaetognaths ind./1000 m3 were also detected for the salp Eukrohnia hamata and Sagitta gazellae. Salpa thompsoni (385 ind./1000 m3 at Station Amphipods were riebest in species (n= 18), No. 228), the euphausiid Euphausia superba followed by fish larvae (n= 12) and (301 ind./1000 m3 at Station No. 221) and coelenterates (n= 11). pteropod Limacina helicina (156 ind./1000 m3 The euphausiid Euphausia at Station No. 169). crystallorophias showed the highest Geographical distribution and relative abundance. The maximum value (568 abundance of the euphausiid species are 3 ind./1000 m ) was obtained from the shown in Figure 3 a-c. Euphausia superba Pesq. antdrt. bras., 1 (1), 1989 8 UWE PIATKOWSKI was very abundant off the northeastern shelf, revealed three "macrozooplankton provinces", whlch is influenced by the East Wind Drift. In each with characteristic communities (Fig. 4a). contrast, Euphausia crystallorophias occurred On the basis of the euphausiid almost exclusively at stations on the shelf, distribution I will introduce the different especially on its southern part. Thysanoessa communities and discuss, how they are related macrura preferred the oceanic stations far off to those known from waters off the Antarctic the continent and was rarely found on the Peninsula. shelf regions. Six euphausiid species have a The dendrogram derived from cluster circumpolar distribution south of the Antarctic analyses for similarity comparisons between Convergence: Euphausia superba, E. frigida, sample compositions (Fig. 4b) revealed three E. triacantha, E. crystallorophias, macrozooplankton communities presented in Thysanoessa macrura and T. vicina (Dzik and Figure 4a: an "oceanic community" (A), Jazdzewski 1978). Only three of them were dominated by gelatinous species and with encountered in the Weddell Sea: E. superba, Thysanoessa macrura as the pre':'ailing E. crystallorophias and T. macrura. Each euphausüd, a "northeastern community" (B), represents a different community. T. macrura where also the isolated samples of the shallow characterizes the "oceanic community" (A), shelf stations 199, 215 and 218 were included, related to the stations in the central Weddell with either Euphausia superba or Euphausia Sea and to those from the deeper parts of the crystallorophias as the dominating component continental slope off the northeastern shelf. and a "southern shelf community" (C), where These stations are either influenced by the Euphausia crystallorophias dominated and the East Win td Drift or situated in the warmer gammarids Eusirus propeperdentatus and surface waters within the Weddell gyre. T. Epimeriella macronyx occurred. macrura was most abundant at these stations, Table I presents the occurrence of each other typical members of this community were taxon in the vmious communities. The gelatinous species Iike Salpa thompsoni, geographical distribution and relative Atolla wyvillei, Vogtia serrata and Sagitta abundance of the euphausüds as weil as of marri. These species are typical inhabitants of two typical community inhabitants are given: the Warni Deep Water, which does not occur Eusirus propeperdentatus for the ''southern on the shelf regions. They can undertake shelf community" (Fig. 5a) and the diurnal migrations from the Warm Deep Water chaetognath Sagitta marri for the "oceanic during daytime to the upper surface layers at community "(Fig. 5b). night. The "oceanic community" is largely identical with that known from the oceanic waters off the Antarctic Peninsula. In a study DISCUSSION of the Ross Sea Marr (1962) emphasized that For the f:rrst time a comprehensive list of E. superba is very abundant in the deep water macrozooplankton species of the Weddell Sea off the slope region. In the present study the · maximum krill concentration (301 ind./1000 is available. With the exception of a hltherto 3 m ) was also found off the slope region (Fig. not definitely identified gastropod larva (Echinospira sp.), wich appears to be a stage 3a). However, krill is not a typical inhabitant new to science, all taxa Iisted in Table I have of the "oceanic community". 3 been previously reported from the Southern Rich krill samples (?- 10 ind./1000 m ) Ocean. were detected in the "northeastern The cluster analysis was applied as a community". In this community E. superba useful technique to identify biotic patterns of was a main component, occurring also at data sets from biological surveys (Field et al. stations on the narrow northern shelf, which 1982). Recently Miller (1985) successfully was also reported by Siegel (1982). Fevolden applied this method by analysing (1980) suggests an active interchange between macroplankton compositions of two the cold shelf water and the Warm Deep Water sub-Antarctic islands (Gough Island and in this area, which would explain the Prince Edward Island). occurrence of E. superba on the shelf. At In the present study the cluster analysis stations with water depths less than 300m E. Pesq. antart. bras., 1(1), 1989 MACROZOOPLANKTON COMMUNITIES FROM WEDDELL SURFACE WATERS 9 crystallorophias was more abudant than E. "Polarstern" by a Reetangular Midwater Trawl (RMT 1 + 8), mesh size 4.5 mm. The RMT 8 was employed because of its superba. No typical "Leitformen" can be 2 !arge net opening of approximately 8 m , which considerably reported from this community, it appears tobe a reduces net avoidance effects. mixture of the "oceanic" and the "southem Seventy taxa were identified. First resu!ts on species shelf'' communities. The "northeastern composition as weil as relative abundance and geographical community" is largely influenced by the East distribution of key species are presented. Cluster analysis revealed three provinces, characteriz­ Wind Drift. lts main water transport flows ed by different macrozooplankton communities: an "ocea­ along the shelf-ice into a southwesterly nic community" dominated by gelatinous species (e.g. Sa/pa direction. When the water masses reach the thompsom), a "northeastern community", where the eu­ phausiids Euphausia crystallorophias and Euphausia superba slope of the southem shelf (north of Halley were the major constituents, and a "southern shelf commu­ Bay, at approximately 75°S), the main brauch nity", where Euphausia c1ysta/Jorophias and the pelagic is deflected to the northwest, where it enters gammarid Eusirus propeperdentatus prevailed. the great Weddell gyre. South of Halley Bay only a narrrow coastal current continues in a southerly direction (Gill 1973). At the REFERENCES divergence of those currents there is a distinct BÖLTER, M., MEYER, M. & PROBST, B., (1980), A statistical scheme for structural analysis in marine ftontier, which separates the "northeastern .. ecosystems. Ecol. Modell.,9: 143-151. community" from the "southem shelf BOLTER, M. & MEYER, M., (1983), The Sandy Beach community" (Fig. 4a). This frontier was also Area of Kiel Fjord and Kiel Bight (Western Baltic identified during phytoplankton community Sea) - A Structural Analysis of a Shallow Water Ecosystem. In: MCLACHLAN, A.& ERASMUS, T. analyses in austral summer 1982/83 (v. (Eds.): Sandy Beaches as Ecosystems. Junk Bröckel 1985). Publishers, The Hague, 263-270. The "southem shelf community" was BOLLMANN, A., (1934), Die Chätognathen der Deutschen characterized by neritic species. E. Antarktischen Expedition auf der "Deutschland" (1911112). Int. Revue d. ges. Hydrob. u. Hydrogr., 30: crystallorophias was the dominant euphausiid, 251-305. which has been known to be restricted to the BRÖCKEL, K. v., (1985), Primary Producdon Data from high-Antartic shelf regions the Sauth-Eastern Weddell Sea. Polar Bio!., 4: 75-80. CARMACK, E.C. & FOSTER, T.D., (1975), Circulation (Rakusa-Suszczewski and Stepnik 1980). and distribution of oceanographic properties near the Ohter typical inhabitants were the gammarids Filchner Ice Shelf. Dee~ea Res., 22: 77-90. Eusirus propeperdentatus and Epimerielia DRESCHER, H.E., HUBOLD, G,, PIATKOWSKI, U., macronyx the latter being an indicator species PLÖTZ, J, & VOSS, J,, (1983), Das Biologische Programm der Antarktis-I-Expedition mit FS of this community. Among the fish larvae "Polarstern", Ber. Po/aiforsch., 12: 1-34. Pleuragramma antarcticum and Aethotaxis DZIK, J. & JAZDZEWSKI, K., (1978), The euphausiid mitopteryx dominated, and adult P. antarcticum species of the Antarctic region. Pol. Arch. liydrobiol., occurred in the surface layers. Coelenterate 25: 589-605. FEVOLDEN, S.E., (1979), Investigations on Krill species were sparse. Most of the prevailing (Euphausiacea) sampled during the Norwegian species of this community are known to live Antarctic Research Expedition 1976177. Sarsia, 64: close to the bottarn on the shelf regions of the 189-198. Antarctic Peninsula. However, on the southem FEVOLDEN, S.E., (1980), Krill off Bouvetöya and in the Southern Weddell Sea with a Description of Larval shelf of the Weddell Sea they characterize the Stages of Euphausia crystallorophias. Sarsia, 65: 149 pelagic ecosystem. -162. FJELD, J.G., CLARKE, K.R. & WARWICK, R.M., (1982), A practical Strategy for analysing multispecies ACKNOWLEDGEMENTS distribution patterns, Mar. Ecol. Prog, Ser., 8: 37-52, I thank Drs. E. Boysen-Ennen, H.G. GILL, A.E., (1973), Circulation and botton water Andres, G.H. Hubold, C.F.E. Roper and R. production in the Weddell Sea. Deep-Sea Res., 20: 111-140. Weigmann-Haass for their help in the species HEMPEL, G., (1983), Die Expedition ANTARKTIS-I mit identification and Dr. M. Meyer for making FS "POLARSTERN" 1982/83. Ber. Po/aiforsch., available his computer programmes. 14: 1-141. HEMPEL, I., HUBOLD, G., KACZMARUK, B., KELLER, R. & WEIGMANN-HAASS, R., (1983), SUMMARY Distribution of some groups of zooplankton in the In austral summer 1982/83 macrozooplankton was inner Weddell Sea in summer 1979/80. Ber. sampled from surface waters (hau! depth ~ 300m) in different Po/aiforsch., 9: 1-36. regions of the Weddell Sea. The samples were Iaken during HUBOLD, G., (1984), Spatial Distribution of Pleuragramma the first German Antarctic expedition onboard the RV artarcticum (Pisces: Nototheniidae) near the Filchner- Pesq. antart. bras., 1 (1), 1989 10 UWE PIATKOWSKI

and Larsen Ice Shelves (Weddell Sea/Antarctica), Sub-Antarctic Is/ands. In: SIEGFRIED, W.R., Polar Bio/., 3: 231-236. LA WS, R.M, & CONDY, P ,R, (Eds.): Antarctic HUBOLD, G., (1985), The early life-history of the nutrient cycles and food webs, Springer, Berlin, New high-Antarctic süverfish P/euragramma antarcticum. York, pp. 355-361. , In: SIEGFRIED, W.R., LAWS, R.M., & CONDY, RAKUSA-SUSZCZEWSKI, S. & STEPNIK, R., (1980). P .R., (Eds.): Antarctic nutrient cycles and food webs. Three species of Krill from Admirality Bay (King Springer, Berlin, New York, pp. 445-451. George, Shouth Shetlands) in summer 1978/79, Po/, KELLER, R., (1983), Contributions to the ear1y life history Arch.Hydrobiol., 27:273-284. of P/euragramma antarcticum Boul. 1902 (Pisces, ROE, H.S.J. & SHALE, D.M., (1979), A New Multiple Nototheniidae) in the Weddell Sea. Meeresforsch., 30: Midwater Trawl (RMT 1 +SM) and Some 10-24. Modifications to the Institute of Oceanographic MARR, J,W,S., (1962), The natural history and geography Sciences' RMT 1 +8. Mar. Bio/., 50: 283-288. of the Antarctic Krill (Euphausia superba Dana), SIEGEL, V., (1983), Investigations on Krill (Euphausia Discovery Rep., 32: 33-464. superba) in the southem Weddell Sea. Meeresjorsch., MILLER, D.G.M., (1985), Marine Macra-Plankton of Two 29: 244-252.

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