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Macrobenthos of the Bay and adjacent shelf

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Macrobenthos of the Ob Bay and adjacent Kara Sea shelf

Andrey A. Vedenin • Sergey V. Galkin • Vladislav V. Kozlovskiy

Received: 11 April 2014 / Revised: 29 December 2014 / Accepted: 30 December 2014 Ó Springer-Verlag Berlin Heidelberg 2015

Abstract The southeastern part of Kara Sea is a highly area of the brackish-water and the marine complexes dynamic area influenced by freshwater masses of Ob and demonstrated the gradual transition. Salinity, correlated Yenisei rivers. It is possible to estimate the annual changes with the temperature, was the most important environ- of bottom communities in such areas by studying the mental factor influencing the benthic communities along temporal and spatial distribution of benthic organisms. In the Ob Bay. The other factors were the sediment structure the previous studies of the same areas, the communities and depth. differing essentially in the composition and abundance were described mainly due to the different sampling Keywords Kara sea Ecology of benthic communities methods employed and possible temporal changes in the estuaries macrobenthos. The aims of this study were to redescribe the benthic communities in the area of the Ob Bay and the adjacent Kara Sea shelf by using trawl and grabs, to Introduction compare the results obtained with these gears with each other and to reveal the environmental factors influencing The Kara Sea is characterized by a number of unique the macrobenthos. Samples were taken along the transect hydrological peculiarities that distinguish it from other from the northern half of the Ob Bay to the central part of polar seas. Two biggest Siberian Rivers, the Ob and Yen- the Kara Sea. Total biodiversity generally increased toward isei, flow into the Kara Sea causing a substantial decrease the open shelf regions. The data obtained only partly in salinity in the upper sea layer. These rivers discharge confirmed the previously recorded trend of gradual sub- about 30 % of the total annual arctic rivers runoff. The stitution of crustacean communities by communities dom- other significant features of the Kara Sea are the strong inated by bivalves and echinoderms. Three community seasonality in the solar regime and in the sea ice-cover and complexes were distinguished in the studied area—the the inflow of the warmer Atlantic waters from the north freshwater, the brackish-water and the marine. The contact (Schauer et al. 2002; Deubel et al. 2003). The history of the Kara Sea investigations begins with the expedition of Nordenskjøld on the whaler ‘‘Vega’’ in Electronic supplementary material The online version of this article (doi:10.1007/s00300-014-1642-3) contains supplementary 1878–1879. The first general description of the sea and the material, which is available to authorized users. overview of the previous scientific expeditions were first published by Pergament (1944), and after that by Zenke- & A. A. Vedenin ( ) S. V. Galkin V. V. Kozlovskiy vich (1963). The first scientific expedition after the World P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovsky Pr., 36, Moscow 117997, War II was realized only in 1975 on the RV ‘‘Vychegda.’’ e-mail: [email protected] The results about the benthic communities, species distri- S. V. Galkin bution and biogeography were published by Antipova and e-mail: [email protected] Semenov (1989). The most intense investigations in the V. V. Kozlovskiy southern parts of the Kara Sea including the Ob and e-mail: [email protected] Yenisei estuaries began in the 1990 s. The major results 123 Polar Biol about the structure of benthic communities in this area there is no influence of the river runoff, the brittle star were obtained during the cruises of RV ‘‘Dalniye Zelentsy’’ Ophiocten sericeum community appears to dominate in 1991 and 1993 (Jørgensen et al. 1999; Denisenko et al. occupying the most part of the entire Kara Sea shelf 2003), RV ‘‘Dmitry Mendeleev’’ in 1993 (Galkin 1998) (Zenkevich 1963). and RV ‘‘Boris Petrov’’ in 1997, 1999 and 2000 (Deubel Despite the great number of studies carried out in the Ob et al. 2003). Bay, a lot of questions remain unsolved. Almost all pre- Benthic fauna is the most slow-reacting component to vious samples were collected either only by grabs or only environmental changes in the highly dynamic estuarine by trawls. Grabs are typically used for the quantitative ecosystem. The development rate of benthic organisms is analysis. Some authors considered the trawl samplings fit rather low; most of the species in polar estuarine regions for the quantitative evaluation by using the attached are euryhaline, slow-growing, and their lifespan varies underwater cameras or DGPS systems, but such methods from several years for polychaetes and crustaceans (Zettler appeared not enough accurate (Eleftheriou and Moore 1997; Jacobson and Sundelin 2006) to decades for mol- 2005). Therefore trawls are usually used either for quali- lusks (Skarlato 1987). Therefore it is possible to estimate tative samplings or for estimating the proportions of each the annual changes in such areas by studying temporal and taxa density and biomass. The samples collected by grabs spatial distribution of benthic species (Galkin 1998). and trawls significantly differ in the species composition, One of the most significant factors that determine the and therefore the occurrence of different communities at structure of benthic communities in estuaries is salinity. the same places was often reported. Grabs usually under- Different studies conducted in the estuarine regions show estimate the role of large-sized and rare species, while that species diversity increases together with salinity when trawls may underestimate the role of small-sized abundant going off from the river mouths (Remane 1934; Zenkevich species. The main reason for this difference is the unequal 1963; Antipova and Semenov 1989; Denisenko et al. 1999, sampling area of the two gears (Galkin 1998; Galkin et al. 2003). The lowest diversity is observed in the brackish- 2010). water area (\5 psu). Khlebovich (1974) suggests the The first aim of our work was to study the macrobenthos salinity level of 5–8 psu to be critical as species diversity structure of the Ob Bay and the adjacent Kara Sea shelf by decreases rapidly within this range of salinity (Khlebovich using both trawl and grabs. We defined the bottom com- 1974; Khlebovich and Komendantov 1997). In addition, munities in the studied area and compared our data from some shallow-water zones of the Arctic estuaries may grabs with the data from trawls. In order to estimate the freeze to the seabed, which results in the destruction of possible temporal changes in the macrobenthos, we com- benthic fauna (Zenkevich 1963). The rate of sedimentation pared our results with the previous studies in this region. In observed in the mouth of Siberian Rivers is high, which addition, we studied the correlation of the macrobenthos apparently influences the benthic fauna (Lisitzin 1994; distribution with the influence of the different environ- Shevchenko et al. 1997; Gaye et al. 2007). As an example, mental factors to determine which of the factors are the the terrestrial organic carbon accumulation in the area of most significant. The second aim of our work was to use a the Yenisei estuary decreases more than 30 times when special approach to describe benthic communities. Tradi- going off from the river mouth toward the central Kara Sea tionally the faunal associations are analyzed in relation to (Gaye et al. 2007). The other factors influencing benthos in abundance and biomass (Jørgensen et al. 1999). We used in both estuarine and marine communities are depth, sediment addition the so-called metabolic (respiration) species rate structure (Jørgensen et al. 1999), chemical parameters of (Alimov 1979) as a main criterion for the community the near-bottom water and underwater currents (Zenkevich description and as a base for statistical analysis. 1963; Semionov 1989). The latter factor is usually difficult to measure, but its presence may be indirectly confirmed by Study area the dominance of sestonophagous species (Thistle et al. 1985) or by the structure of sediments (Allen 1984). The Kara Sea is one of the polar seas lying between Novaja There is a trend of gradual substitution of communities Zemlja where it borders the and Severnaja in the area of the Kara Sea estuaries. The inner parts of the Zemlja where it borders the Laptev Sea. The investigated Ob and Yenisei Bays are mainly populated by a crustacean area included the Ob Bay, which spreads over a thousand community (amphipods Pontoporeia spp. and isopods kilometer from approximately 66°Nto73°N, and the Saduria entomon). Further north, several species of bivalve adjacent part of the Kara Sea shelf. The region of the Ob dominate, especially Portlandia arctica (Lubina 2000; Bay and adjacent shelf is one of the best studied in the Kara Denisenko et al. 2003; Galkin et al. 2010). Further out from Sea. The water column in the mouth of the bay is highly the bays, the cumacean Diastylis sulcata is very abundant, stratified despite being shallow (\50 m), with a rather even dominant in some places (Deubel et al. 2003). Where smooth bottom relief (Deubel et al. 2003). The level of the 123 Polar Biol primary production here is much higher than in the 50 to 80 m at the shallow-most stations to 200–250 m at northern parts of the sea (Demidov et al. 2014). The surface the deepest stations. A single trawl was taken at each sta- waters of the bay are less transparent, less saline and tion. In addition, the ‘‘Ocean-0.1’’ grabs with 0.1-m2 usually have the different temperature (depending on the sampling area were used in both expeditions. Three to five season) comparing to the deeper waters (Demidov et al. grabs were taken at each station in 2007, including all the 2014). Salinity and temperature of both the upper and the stations with trawls. One to five grabs were taken at each near-bottom water layers depend on the Ob and Taz rivers station in 2010. The number of the grab samples differed runoff, which is influenced by season. The highest volume due to the weather conditions and unequal a-diversity in of freshwater is observed between May and July in this part the inner and outer parts of the Ob Bay. The list of samples of Kara Sea comprising about 80 % of the total annual taken by grabs and trawls is shown in the Table 1. Trawl river runoff of the Ob and Taz rivers (Pivovarov et al. samples were washed through a set of sieves with a mesh 2003). Besides annual seasonal changes in salinity and size of 5mm and 1 mm. Grab samples were washed using a temperature, there are some long-term variations over 0.5-mm mesh size sieve. All samples were fixed in 6 % several years. For instance, in 2000, an unusually high buffered formaldehyde. salinity level, almost 31 psu, was observed in the mouth of The material was identified to species level wherever the Ob Bay, while in the previous years, salinity was \29 possible. The identification keys from Zhirkov (2001) were (Deubel et al. 2003). Most of the sediments in this area are used for polychaetes, from Lomakina (1958) for cuma- derived from the river runoff and are fine sands or silts. ceans, from Gurjanova (1951) for amphipods and from Further out from the bay, the river runoff influence Gaevskaya (1948) for other invertebrates. All specimens of decreases. The main sedimentation occurs around the area at each species were counted and weighed (wet weight; 73°N–74.5°N. This can be explained by the ‘‘marginal fil- mollusks and echinoderms were weighed without decalci- ter’’—a term proposed by Lisitzin (1994) to describe pro- fication) after sorting. Using the allometric relationship cesses which take place in the continent–ocean boundary between individual metabolic rate R and mean wet body zone. At a global scale, this zone involves estuaries and river mass W of the form R = aWb, and assuming b = 0.75 mouths. A basic feature of the marginal filter is a river–sea (Peters 1983; Ernest et al. 2003), we calculated the meta- geochemical barrier with sharp gradients of current veloci- bolic (respiration) rate Ri for every species by the equation: ties, water salinity and temperature. A main mass ([90 %) of R ¼ a B0:75N0:25 riverine suspended particulate matter is removed from water i i i i as a result of various physical, chemical and biological where Ni and Bi are the i-th species abundance and biomass processes in the marginal filter zone. These processes pri- per unit area, and ai is the taxon-specific, mass-independent marily include flocculation and coagulation of the suspended metabolic normalization constant (taken here as specific -1 -1 material together with sorption and, as a result, sedimenta- respiration rate, mg O2 g h ). The ai values were taken tion (Lisitzin 1994). Northward from this area, the sediments as 0.133 for crustaceans, 0.08 for sponges, bryozoans and are represented by silts with high proportion of clay; the sea- echinoderms, 0.115 for annelids, nemerteans, priapulids bottom is extremely flat (Zenkevich 1963). The depth and cnidarians, 0.126 for gastropods and scaphopods, and increases gradually to 40–50 m at about 75.3°N where a 0.079 for bivalves (Alimov 1979). Then, the relative met- threshold is located. After the threshold, the depth rapidly abolic rate for a species i was calculated as a proportion of increases to 150–160 m (Fig. 1). the total: ri = Ri/R Ri (Kucheruk and Savilova 1985; Az- ovsky et al. 2000, 2004). Metabolic rate is a more desirable measure for population-level energy use than density or Materials and methods biomass, since abundance may underestimate and biomass overestimate the role of rare but large-sized forms. The The material was collected during the 54th cruise of R/V relative metabolic rate shows only the percentage of each ‘‘Akademik Mstislav Keldysh’’ in September, 2007 along taxa. Therefore it is possible to use it in the trawl data the submeridianal section northward from the mouth of Ob where an accurate estimation of the density and biomass is Bay and during the expedition of the tugboat ‘‘OTA-777’’ in hardly possible. For this reason, ri values were used in August, 2010 investigating the area from the mouth of Taz further calculations to characterize the relative species Estuary to the Shokalsky Island. Seven trawl stations were contribution to community production and metabolism. made in 2007 and 38 grab stations in 2007 and 2010 (Fig. 1). Statistical analyses were performed in MS Excel 2007, We used a Sigsbee trawl with frame size 150 9 35 cm, PRIMER V6 (Clarke and Warwick 2001) and PAST V3 the inner net with 0.5-cm mesh size for macro- and (Hammer et al. 2003) programs for data analysis. Trawl megafauna sampling. Trawling was conducted at a drifting and grab data were treated separately. Species richness was speed of 0.2–1 knots. The distance of trawling varied from calculated as a total number of the species in each grab 123 Polar Biol

Fig. 1 Region of the Ob Bay and adjacent part of the Kara Sea shelf with stations investigated sample (abundance data). The species diversity was esti- either of the gears. The canonical correspondence analysis mated using the Shannon index and the Hurlbert rarefaction (CCA) was performed to estimate the contribution of the index for 100 individuals. Evenness was calculated using the environmental factors in species composition (McCune et al. Pielou index. The species–individuals accumulation curves 2002). The environmental data including the sediment were plotted. We provided cluster analysis (UPGMA algo- granulometry, organic carbon concentration, near-bottom rithm) and multi-dimentional scaling (MDS) basing on the temperature, salinity, oxygen concentration and pH were Bray–Curtis, Jaccard and Sørensen similarity indices (the determined during the same expeditions. metabolic rate data were used for both grab and trawl sam- ples). The results of the cluster analysis and the ordination were verified by ANOSIM analysis in order to reveal dif- Results ferent benthic communities. We used the SIMPER analysis of the species lists (the ri values) from the trawl and grabs in Coordinates and environmental data for each station are order to understand which species are underestimated in shown in Table 1. A total number of 48,308 individuals

123 Polar Biol

Table 1 Number of gears taken (G—Ocean-0.1 grab; T—Sigsbee trawl), sampling time, latitude, longitude, depth, sediment structure, clay fraction (the upper 1 cm, grain size \ 1 lm), bottom-water temperature, salinity, oxygen level and pH at each station Station Gear Month/ Latitude Longitude Depth Sediment Clay Temp. Salinity Oxygen pH Year (N) (E) (m) (the upper 5 cm) (%) (°C) (psu) (ml/l)

2 1G 08/2010 68.4043 74.0758 -11.4 Very fine sand with silt 6.53 11.01 0.00 6.66 7.55 4 1G 08/2010 68.492 73.6227 -6.6 Fine-grained sand with silt 2.38 9.79 0.00 7.14 7.61 5 1G 08/2010 68.553 73.839 -12.2 Very fine sand with silt 4.24 11.37 0.02 6.62 7.54 6 1G 08/2010 68.6795 74.1789 -11.7 Very fine sand with silt 4.92 8.78 0.03 7.09 7.48 8 1G 08/2010 68.8656 74.3165 -11.2 Very fine sand with silt 5.51 6.82 0.04 7.52 7.64 10 1G 08/2010 69.0599 73.9991 -8.4 Fine silt 10.71 7.51 0.04 7.42 6.9 15 1G 08/2010 68.9282 73.0853 -10.8 Fine- and average-grained sand 1.35 8.65 0.05 7.09 7.63 17 1G 08/2010 69.2997 73.5717 -13.6 Very fine sand with silt 4.84 8.76 0.05 7.28 7.6 23 1G 08/2010 69.8049 72.9877 -17.8 Fine- and average-grained sand 1.50 4.45 0.04 8.56 7.71 25 1G 08/2010 69.9369 73.4811 -13.4 Silt 7.01 4.71 0.03 8.28 7.34 27 1G 08/2010 70.1047 73.4729 -22.7 Fine- and average-grained sand 1.41 4.97 0.03 8.18 7.4 31 1G 08/2010 70.5087 73.0672 -9.6 Fine-grained sand 0.96 5.13 0.06 8.85 8.17 33 1G 08/2010 70.7471 73.6831 -19.5 Very fine sand with silt 4.97 4.2 0.07 8.48 7.69 37 1G 08/2010 70.9492 73.1402 -19.3 Fine-grained sand 3.00 4.46 0.1 8.36 7.83 39 1G 08/2010 71.1095 72.8261 -16.3 Average-grained, well-sorted sand 0.39 4.38 0.48 8.75 7.49 40 1G 08/2010 71.2157 72.9116 -25.8 Fine silt 15.93 3.75 0.07 8.36 7.29 41 1G 08/2010 71.2863 72.972 -12.2 Fine silt 9.85 1.93 0.2 8.11 7.36 43 3G 08/2010 71.4012 72.7373 -11.8 Fine-grained, well-sorted sand 0.38 3.84 0.16 8.88 7.59 44 2G 08/2010 71.4484 72.4368 -22.3 Fine-grained sand with silt 4.41 3.12 0.16 8.49 7.56 45 3G 08/2010 71.4727 72.2314 -17.4 Fine-grained sand 2.22 3.55 0.29 8.68 7.81 47 5G 08/2010 71.6051 72.4975 -20 Fine- and average-grained sand 3.55 3.73 0.37 8.53 7.55 48 5G 08/2010 71.6868 72.9532 -17.9 Fine silt 6.93 3.03 0.31 8.55 7.61 50 5G 08/2010 71.8335 73.08 -18.3 Very fine sand with silt 4.42 3.29 0.23 8.58 7.76 51 3G 08/2010 71.918 72.8271 -16.7 Fine-grained sand 2.36 3.33 0.42 8.42 7.74 53 5G 08/2010 72.2077 73.4357 -13.1 Very fine sand with silt 5.83 2.72 4.05 8.61 7.51 54 5G 08/2010 72.3793 74.0018 -12.3 Very fine sand with silt 6.58 -0.07 23.76 7.27 7.66 55 5G 08/2010 72.5616 74.6021 -14.6 Fine-grained sand 1.54 -0.8 28.78 7.53 7.42 57 5G 08/2010 72.6668 73.9437 -20.5 Fine silt 17.78 1.28 31.08 8.08 7.68 58 3G 08/2010 72.6704 73.6841 -21 Silt 5.83 -1.27 30.84 8.48 7.75 4993 3G 09/2007 71.2483 72.865 -20 Fine silt 5.00 7.2 0.05 8.07 7.42 4994 1T; 3G 09/2007 71.7333 72.7883 -16 Fine silt 5.52 6.05 0.86 8.2 7.52 4995 1T; 3G 09/2007 72.1667 73.2383 -11 Silt 7.12 4.35 8.69 7.13 7.53 4996 1T; 3G 09/2007 72.57 73.8217 -15 Silt 7.30 2.24 24.44 7.36 7.83 4999 1T; 5G 09/2007 72.9533 73.285 -26 Clayey silt 19.60 0.09 29.53 6.94 7.86 5000 1T; 5G 09/2007 73.7517 72.9433 -27 Clayey silt 20.43 0.8 32.13 5.64 7.77 5001 5G 09/2007 74.5833 72.7583 -24 Clayey silt 21.06 -1.21 32.71 5.92 7.87 5002 1T; 5G 09/2007 75.1683 72.6083 -29 Average-grained, well-sorted sand 0.00 1.15 32.29 6.83 7.92 5003 1T; 5G 09/2007 75.44 72.5317 -55 Silt 7.82 1.13 32.85 7.03 8 from 200 macrobenthic taxa were found in the samples. which counts not only presence/absence of each species but

Most of the stations are represented only by the grab also ri value. samples, so we consider the grab and trawl samplings separately. The qualitative similarity indices (Jaccard and Grab data Sørensen) were not appropriate for both grab and trawl data due to the similar species composition at some stations. A total of 38712 individuals from 110 macrobenthic taxa Thus we decided to use the quantitative Bray–Curtis index were found (from 3 to 39 per sample station) in 103 grab

123 Polar Biol samples with a total surface area of 10.3 m2. The total priapulids Halicryptus spinulosus, cumaceans D. sulcata biomass in the samples varied from 0.04 (station 41) to and lesser role of the polychaetes M. arctia. Interestingly, a 147.3 g/m2 (station 58). The density varied from 60 (sta- lot of dead shells from P. aestuariorum were present at tions 41 and 43) to 20460 ind./m2 (station 40). these three stations, while only a few living specimens We could distinguish three large community groups were found. The amount of D. sulcata at station 54 was using the cluster and MDS analyses: the freshwater group exceptionally high reaching almost 70 % ri. This station is (8 stations); the brackish-water group (21 stations); the separated both on the dendrogram and on the ordination marine group (9 stations) (Figs. 2, 3). The spatial distri- from other stations of the complex (Figs. 2, 3). The mean bution of the community groups is shown in Fig. 4, and biomass of the entire brackish-water complex was 21.86 g/m2. their characteristics are summarized in Table 2. The ri A total of 18 species were found in this complex, and the values of the main taxa distribution in each complex are diversity was much higher than in the freshwater complex shown in Fig. 5a. The total species number in each com- (Table 3). plex and the values of the Pielou, Shannon and Hurlbert The most diverse and versatile was the marine complex rarefaction indices are shown in Table 3. The species (stations 4996–5003 and 55–58) with more than a hundred accumulation curves for each complex are shown in Fig. 6. species detected. The values of the Shannon and Pielou The freshwater complex (stations 2–17) was character- indices were the highest here (Table 3). Bivalves played ized by the dominance of oligochaetes (mainly Potamo- the major role within this complex except for the two thrix hammoniensis) and chironomid larvae. Other groups northernmost stations. At stations 4996, 5000 and 55–58, present at these stations included bivalves (different spe- P. arctica dominated (40–69 % ri). At station 5001, Astarte cies of Pisidiidae) and crustaceans (Mysis relicta and borealis dominated (45 % ri). Musculus niger played a gammarid amphipods). The mean biomass at these stations notable role at the stations 4999, 5001 and 58 (20–30 % ri). was 6.04 g/m2. This was the least diverse complex with Its colonies formed a byssus raft to maintain their position only seven species found and ES(100) \ 4. on the soft bottom. The mean biomass was rather low at The brackish-water complex (stations 4993–4995 and stations 4996, 55 and 57 (from 12.9 to 25.0 g/m2) and 23–54) was characterized by the dominance of the poly- much higher at stations 4999–5000 and 58 (from 49.5 to chaete Marenzelleria arctia. Oligochaetes (Potamothrix 147.3 g/m2). At the southernmost stations (4996, 55 and spp.) and the polychaete, Ampharete vega, also play a 57), the polychaete Trochochaeta carica played notable major role in community. Isopods S. entomon and amphi- role, while from all the other stations, it was absent. Pria- pods Onisimus birulai and P. femorata were present at the pulids H. spinulosus were present at three southernmost most of the stations within the complex. Three northern- stations, and the cumaceans D. sulcata were abundant. The most stations (4995, 53 and 54) differed in species com- station 5002 was unique for the Kara Sea. Sediments at position from the other stations by the presence of the this station were represented by very well-sorted sands

Fig. 2 Dendrogram showing grouping of the grab stations based on a cluster analysis of species ri values (Bray–Curtis similarity). Three station complexes are shown

123 Polar Biol

Fig. 3 Ordination showing the grab stations based on the MDS analysis of species ri values (Bray–Curtis similarity). Two levels of the Bray–Curtis similarity are shown (5 and 10)

typical species were brittle stars O. sericeum, bivalves A. crenata and Similipecten greenlandicus and polychaetes Spiochaetopterus typicus. This station had the highest species diversity, 32.4 on the average. The biomass was high at 49.5 g/m2. Despite the large dispersion of stations on the ordination within the brackish-water and marine clusters (Fig. 3), all the three complexes are supported by the ANOSIM analysis (Table 4). The separation is statistically significant at the level of 0.1 %. The species accumulation curve showed the ten- dency to reach the saturation point for each of the complexes (Fig. 6). Increasing the number of samples would not signif- icantly increase the number of species. The whole species list

with the ri values is shown in the Online Resource 1. Results of the CCA analysis are shown in Fig. 7. There is a compact aggregation of the stations located in the inner part of the Ob Bay (stations 2–53, 4993–4995). These stations are similar in a rather high near-bottom tempera- ture and very low salinity. The difference is mostly in depth, clay content and the oxygen level (Table 1). All the characteristic freshwater and brackish-water species (P. hammoniensis, Chironomidae gen.spp., Pisidium sp., M. arctia, A. vega, O. birulai) are located in the same area of Fig. 4 Stations located in the area of the Ob Bay with the three the plot. The northernmost brackish-water station 54 and macrobenthic communities shown. Borders between the communities the marine stations 55–58 and 4996–5001 form a less are marked with dotted lines; isohalynes are marked with continuous distinct aggregation at the opposite side of the CCA plot. lines These stations are characterized by a higher salinity and a lower near-bottom temperature. The bivalves P. arctica, M. (Table 1). The dominant species were the polychaete niger and A. borealis are located within these stations. The Ophelia limacina, the sea anemone Urticina felina and two northernmost stations of the marine complex 5002 and another polychaete Travisia forbesii. The biomass was 5003 are placed separately from all other stations. quite low at 24.4 g/m2. The northernmost station (5003) was made at a depth of 55 m. Grab samples were similar to Trawl data the typical O. sericeum community. The sipunculid Phas- colion strombus, polychaetes Maldane sarsi and Aglaoph- A total of 9,596 individuals belonging to 159 macrobenthic amus malmgreni were the dominant species. Among the species were found (from 8 to 102 per station) in trawl 123 Polar Biol

Table 2 List of the main Dominant species Number of specimens Biomass Mean relative dominant taxa, their density, 2 2 (ind./m ) (g/m ) metabolic rate (ri) biomass and relative metabolic rate in the different Freshwater community communities (grab samples). Potamothrix hammoniensis 4,054 (±4660) 3.6 (±3.7) 56.1 (±28.0) Mean values are indicated before brackets; standard Chironomidae gen.spp. 318 (±277) 1.68 (±3.3) 23.6 (±26.7) deviations are indicated Pisidium sp. 166 (±183) 0.65 (±0.8) 9.38 (±11.0) between brackets Unionidae gen.sp. 5 (±7.5) 0.029 (±0.04) 0.27 (±0.43) Mysis relicta 2.5 (±7) 0.02 (±0.05) 0.079 (±0.22) Brackish-water community Marenzelleria arctia 1,205 (±1,620) 10.58 (±17.4) 41.01 (±28.4) Potamothrix sp. 3,534 (±4,571) 3.26 (±4.9) 20.46 (±20.3) Saduria entomon 7(±8) 6.67 (±10.6) 10.92 (±21.3) Ampharete vega 75 (±189) 2.78 (± 6.8) 10.18 (±24.1) Onisimus birulai 76 (±113) 0.16 (± 0.18) 8.17 (±17.2) Marine community (southern part) Portlandia arctica 368 (± 335) 20.06 (±24.2) 41.83 (±29.2) Musculus niger 26 (±27) 16.34 (±21.4) 10.8 (±12.8) Astarte borealis 24 (±61) 7.17 (± 8.9) 6.50 (±17,1) Macoma calcarea 43 (±52) 4.27 (±6.42) 4.55 (±6.32) Station 5002 Ophelia limacina 50 (±33) 2.82 (±1.6) 39.18 (±24.7) Urticina felina 4(±5) 18.7 (±40.1) 23.33 (±35.3) Travisia forbesii 8(±13) 0.97 (±2.1) 7.44 (±16.4) Tharyx sp. 84 (±41) 0.19 (±0.12) 7.38 (±5.73) Station 5003 Maldane sarsi 198 (±67) 3.12 (±1.8) 15.25 (±6.1) Phascolion strombus 2(±4.4) 20.6 (±45.9) 11.38 (±25.5) Aglaophamus malmgreni 4(±5.4) 5.83 (±11.1) 8.89 (±16.5) Spiochaetopterus typicus 120 (±56) 1.61 (±1.2) 8.52 (±6.1)

Fig. 5 Relative metabolic coefficients for different macrotaxa in the different complexes. Freshwater, brackish-water, marine (southern part) complexes and stations 5002 and 5003 are shown separately. a The grab data; b The trawl data

samples. The results of the main taxa distribution (ri val- (percentage abundance and biomass). The relative abun- ues) are shown in Fig. 5b. As it was impossible to estimate dance, biomass and metabolic rate of the main dominant the abundance and biomass, we used relative values species are shown in Table 5.

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Table 3 Total species number, density, biomass and values of Pielou, Hurlbert rarefaction and Shannon indices for each complex (grab data) Complex Total species Total individuals Pielou ES(100) Shannon

Freshwater 7 3,664 0.2372 3.662 0.4615 Brackish-water 18 29,548 0.348 6.047 1.006 Marine 103 5,501 0.7138 31.77 3.308

located in the mouth of Ob Bay, west from Shokalsky Island. The main dominant species here was S. sibirica. The number of echinoderms increased here in comparison with the previous station. The ophiuroid Stegophiura nodosa was among the dominant species. The next station 5000 was similar to the previous one. The main dominants were S. sabini, S. sibirica and P. arctica. A great number of the pelagic mysids M. oculata and amphipods Themisto libellula were found in the trawl sample. The sample from station 5002 was very unusual. It consisted only of the animals, all the sediment was washed away. Most of the organisms were actively moving predators or scavengers (amphipods Acanthostepheia behringiensis and Anonyx nugax); other organisms were active burrowers (cumaceans D. glabra and polychaetes Nephtys longosetosa). We also found many fish as Gymnacanthus tricuspis in this sample, and they were excluded from the analysis. Sedentary organisms were not numerous. At the last trawl station Fig. 6 Species individuals accumulation curves for the grab data 5003 we collected over 100 species. The dominant species from the stations belonging to the freshwater, brackish-water and there was the scallop S. greenlandicus. Other dominants marine complexes were brittle stars O. sericeum and Ophiacantha bidentata, the seastar Urasterias lincki, bivalve A. crenata and poly- The main dominants at the most freshwater trawl station chaetes Flabelligera affinis and Nereis zonata. Notable was 4994 were the isopods S. entomon, the polychaetes M. the large amount of empty tubes from the polychaete S. arctia, A. vega and oligochaetes Potamothrix sp. Isopods typicus. were completely lacking from the next station 4995. The Comparison of the trawl samples using Bray–Curtis dominants there were priapulids H. spinulosus and poly- similarity indices showed several station groups (Fig. 8). chaetes M. arctia. We found a large amount of P. aestu- The most freshwater stations 4994 and 4995 formed an ariorum dead shells. At the next station 4996, another indistinct group. Three stations (4996, 4999 and 5000) species of bivalves P. arctica dominated. The other two were very similar due to the high number of euryhaline species that were numerous in this community were eury- isopods (S. sibirica and S. sabini). Stations 5002 and 5003 haline species of isopods—S. sibirica and S. sabini.This were very specific, and they did not group either together was the first station where echinoderms appeared (the or with other stations. Thus, based on the trawl data ana- holothurian Eupyrgus scaber). The station 4999 was lysis, we can distinguish four station groups: unstable

Table 4 ANOSIM results of the grab samples (ri data) Group pairs R statistic Significance level (%) Possible permutations Actual permutations

Brackish-water–marine 0.956 0.1 14,307,150 999 Brackish-water–freshwater 1 0.1 4,292,145 999 Marine–freshwater 1 0.1 24,310 999

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Fig. 7 Ordination showing the station and species distribution (the grab data) in relation to the six environmental factors based on a CCA analysis. Depth (m), salinity (psu), temperature (°C), clay fraction (%), oxygen (ml/l) and pH are shown brackish-water group with two stations, transitional group Discussion with three stations and two independent stations 5002 and 5003 situated out from the Ob runoff influence area. The Species composition complete species list found in trawl samples is shown in the Online Resource 1. The species composition of the freshwater complex (sta- tions 2–17) corresponds with the previous investigations in Comparison of the trawl and grab data this part of the Ob Bay. Different authors describe benthic communities with the dominance of the oligochaetes, We carried out the SIMPER analysis for those stations that chironomids and freshwater bivalves in the southern half of were represented by both the grab and trawl samples. The the Ob Bay (Leschinskaja 1962; Galkin 1998; Denisenko results are shown in Table 6. The trawl samples appeared et al. 1999). The long-term studies of the freshwater ben- to be more rich in the echinoderms, arthropods and some of thos revealed significant seasonal and annual fluctuations the mollusks. The grab samples were more rich in the of biomass in this area. During 1958–1960, the biomass polychaetes, sipunculids, bivalves and cnidarians. The two varied from 1.24 to 14.73 g/m2 and from 2.33 to 7.36 g/m2 freshwater trawl samples 4994 and 4995 corresponded with during 2002–2009. The biggest values of biomass were the brackish-water complex revealed during the analysis of observed in August–September. The species composition, grab samples. Trawl samples from all the other stations however, remained invariable (Stepanova et al. 2011). corresponded with the marine complex of the grab samples. We suggest that a generally accepted notion about the However, the peculiarity of the two northernmost trawl polychaete and crustaceans communities being replaced by stations was very high. the bivalve and further echinoderm communities is not

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Table 5 List of the main Dominant species Relative Relative Relative dominant taxa, their number, abundance (%) biomass (%) metabolic rate (ri) biomass and relative metabolic rate from the different stations Station 4994 (trawl samples) Saduria entomon 6.1 89.0 75.56 Mysis relicta 36.9 4.9 13.56 Gammaracanthus loricatus 1.9 4.7 6.27 Marenzelleria arctia 48.7 0.8 3.18 Ampharete vega 2.8 0.3 0.67 Station 4995 Marenzelleria arctia 46.5 29.8 44.92 Halicryptus spinulosus 0.5 36.1 16.66 Ampharete vega 4.1 12.8 12.99 Potamothrix sp. 43 3.5 8.83 Gammaracanthus loricatus 0.3 11.0 6.97 Station 4996 Saduria sibirica 2.4 61.7 52.20 Portlandia arctica 85 11.8 21.91 Saduria sabini 0.9 23.2 19.58 Onisimus affinis 1.1 0.6 1.33 Diastylis sulcata 1.3 0.5 1.19 Station 4999 Saduria sibirica 7.6 34.2 36.97 Stegophiura nodosa 46.6 18.2 21.83 Mysis oculata 15.7 4.3 9.36 Saduria sabini 1.2 10.0 9.31 Myriotrochus rinkii 0.9 11.5 5.71 Station 5000 Saduria sabini 6.3 29.1 31.63 Saduria sibirica 3.7 29.0 27.65 Mysis oculata 51.1 5.4 15.07 Urasterias lincki 0.1 20.0 5.58 Colus sabini 0.3 4.4 3.33 Station 5002 Acanthostepheia behringiensis 54.8 36.8 44.63 Nephtys longosetosa 9.3 20.2 15.83 Diastylis glabra 19.3 12.7 15.44 Anonyx nugax 2.7 9.7 7.71 Sabinea septemcarinata 1.3 9.5 6.40 Station 5003 Similipecten greenlandicus 14.8 20.8 23.26 Ophiocten sericeum 33.6 11.8 18.89 Ophiacantha bidentata 5.0 9.3 9.85 Urasterias lincki 0.3 21.6 9.19 Astarte crenata 1.0 6.3 4.93 Nymphon hirtipes 2.7 2.1 4.67 entirely correct. A few studies of benthic communities in the crustaceans S. entomon, O. birulai (Pseudalibrotus the central and northern brackish-water parts of the Ob Bay birulai in older literature) and Pontoporeia spp. played the demonstrate the dominance of various species of crusta- major role (Galkin 1998; Denisenko et al. 1999; Stepanova ceans and polychaetes M. arctia. In the trawl samplings, 2003), while in the grab and box-corer samplings,

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of the brackish-water cluster stations corresponds with the southern macrozoobenthic cluster revealed by Deubel et al. (2003). While the freshwater and brackish-water parts of the Ob Bay benthic ecosystem seem to be stable in time, the northern (marine) part is highly dynamic. Filatova and Zenkevich (1957) described the community with the dominance of P. arctica and A. borealis around the mouth of the Ob Bay. According to the samples collected in the 1991, the bivalves P. arctica and Hiatella arctica domi- nated in the same area (Denisenko et al. 1999). Jørgensen et al. (1999) reported the dominance of P. arctica and the Fig. 8 Ordination showing the trawl stations based on the MDS presence of polychaetes Levinsenia gracilis, Microneph- analysis of species ri values (Bray–Curtis similarity). Two levels of thys minuta, bivalves Yoldiella intermedia, and isopods S. the Bray–Curtis similarity are shown (3 and 40) sabini in the mouth of the Ob Bay (data from 1993 sam- plings). According to Deubel et al. (2003), the cumaceans D. sulcata played the major role in this area (1997–2000 polychaetes M. arctia dominated (Jørgensen et al. 1999; samplings). These variations cannot be explained by the Deubel et al. 2003). These results are probably explained different sampling methods that were similar in these four by the different sampling areas of these gears. Isopods S. studies: the grabs and/or box-corers were used. In our entomon occur in less density than smaller polychaetes, but samples, the bivalves P. arctica dominated in the most of their biomass was more significant. A single large S. ent- the marine complex stations (grab samples) together with omon caught in one grab at station 37 made up 90 % of the the isopods S. sibirica and S. sabini (trawl samples). A. total sample biomass. At the other brackish-water stations, borealis was found only at northern stations of the complex these crustaceans were either absent or juvenile, so their (5000–5003), while no H. arctica and Y. intermedia were biomass did not exceed 20 % of the total sample biomass. found. The cumaceans D. sulcata played a notable role At those stations, M. arctia dominated. The role of the only inside the Ob Bay (stations 4995–4996, 53–55). The amphipods O. birulai and Pontoporeia spp. is usually previous and our data suggest that there could be signifi- underestimated in grab samplings probably due to their cant temporal changes in the structure of benthic commu- ability to escape from the gear before its closure. Inter- nities, which can hardly be explained by the different estingly, different authors report different species of Pon- sampling methods. The three southernmost stations (4996, toporeia in the Ob Bay. Jørgensen et al. (1999) described 55 and 57) seem to be another step of the transition P. femorata as a typical species for Marenzelleria com- between the brackish-water and marine complex making munity, while Denisenko et al. (1999) reported P. affinis in this transition rather gradual than discrete. Different the same area. We did not find a single P. affinis in our authors indicated certain hydrological fluctuations in the samples. Three northernmost stations (4995, 53 and 54) are northernmost area of the brackish-water complex and located on the MDS plot in the upper part of the brackish- southernmost area of the marine complex (Khlebovich and water cluster (Fig. 3). The species composition was slightly Komendantov 1997; Pivovarov et al. 2003; Demidov et al. different at these stations. Another characteristic feature 2014). Deubel et al. (2003) mentioned the significant dif- was the big amount of the P. aestuariorum dead shells, ference between the years 1999 and 2000 when the near- which indicates that there was at least one previous mas- bottom salinity (measured in summer) varied from 27 to sive larval settlement of this species in this area. We 30 psu. In our study, the three-year gap between the sam- believe these shells were several years old, probably from a plings at stations 4995–4996 and 53–58 could influence the recruitment here in 2000, when the salinity level was benthic structure, although the spatial distribution of the unusually high in this part of the Ob Bay, over 28 psu in near-bottom salinity in September 2007 and in August August–September (Deubel et al. 2003). The stations are 2010 was similar (Table 1; Fig. 4). The salinity and other located within the area of the critical salinity level (Khl- environmental fluctuations may influence the bottom ebovich 1974), and the bottom fauna here seems to be communities in this transitional area. transitional between the typical brackish-water complex Similar communities with the dominance of bivalves P. and marine complex. Interestingly, the very similar com- arctica and the isopods Saduria spp. were reported from munity was found in the area of Mackenzie River delta in the area of the Lena delta in Laptev Sea and Mackenzie the Beaufort Sea. Notable was the presence of priapulids H. delta in Beaufort Sea (Schmid et al. 2006; Aitken et al. spinulosus and oligochaetes (Aitken et al. 2008). The most 2008). Apparently, a strong resemblance in the macro- and 123 Polar Biol

Table 6 Results of the Group Species Mean ri Average SD Contribution (%) SIMPER analysis. Comparison dissimilarity of the trawl and grab samples Trawl Grab from 2007 BIV Portlandia arctica 3.29 18.54 9.89 0.72 10.42 ISO Saduria sibirica 17.02 0 8.43 0.81 8.88 POL Marenzelleria arctia 6.89 11.24 7.62 0.69 8.03 OLI Potamothrix sp. 1.27 13.05 6.72 0.6 7.09 ISO Saduria entomon 10.79 1.63 5.93 0.46 6.25 ISO Saduria sabini 8.73 0 4.32 0.74 4.56 AMP Acanthostepheia behringiensis 6.38 0 3.16 0.4 3.33 POL Ophelia limacina 0.03 5.6 2.81 0.41 2.96 POL Maldane sarsi 0.02 5.43 2.64 0.61 2.78 CNI Urticina felina 0 4.72 2.36 0.59 2.49 OPH Stegophiura nodosa 3.38 1.95 2.36 0.57 2.49 BIV Musculus niger 0 4.69 2.34 0.45 2.47 PRI Halicryptus spinulosus 2.43 2.01 1.91 0.59 2.01 MYS Mysis oculata 3.82 0 1.89 0.67 1.99 BIV Similipecten greenlandicus 3.32 0.26 1.73 0.43 1.83 OPH Ophiocten sericeum 2.7 0.9 1.64 0.51 1.72 POL Nephtys longosetosa 2.26 1.4 1.59 0.58 1.67 BIV Macoma calcarea 0.06 3.07 1.54 0.52 1.62 POL Ampharete vega 1.96 1.3 1.39 0.68 1.47 POL Tharyx sp. 0.02 2.57 1.25 0.88 1.32 AST Urasterias lincki 2.11 0.9 1.24 0.72 1.31 CUM Diastylus glabra 2.22 0 1.1 0.41 1.16 POL Trochochaeta carica 0.01 2.13 1.07 0.41 1.13 POL Nephtys paradoxa 0.11 2.05 1.06 0.43 1.12 MYS Mysis relicta 2.01 0 0.99 0.42 1.05 AMP Gammaracanthus loricatus 1.89 0 0.94 0.62 0.99 POL Terebellidae gen.sp. 0 1.58 0.78 0.65 0.82 OPH Ophiacantha bidentata 1.41 0.1 0.73 0.43 0.77 POL Nephtys ciliata 0.22 1.26 0.71 0.47 0.75 Species more significant in DEC Sabinea septemcarinata 1.4 0 0.69 0.59 0.73 grabs are marked with bold POL Bylgides promamme 0.3 1.06 0.6 0.53 0.63 AMP amphipods, AST asteroids, POL Aglaophamus malmgreni 0.02 1.27 0.6 0.41 0.63 BIV bivalves, CNI cnidarians, AMP Anonyx nugax 1.18 0 0.59 0.44 0.62 CUM cumaceans, DEC POL Spiochaetopterus typicus 0 1.22 0.57 0.4 0.6 decapods, GAS gastropods, ISO isopods, MYS mysids, OLI BIV Astarte crenata 0.7 0.62 0.56 0.57 0.59 oligochaetes, OPH ophiuroids, POL Travisia forbesii 0 1.06 0.53 0.4 0.56 POL polychaetes, PRI GAS Buccinum angulosum 0.94 0 0.46 0.4 0.49 priapulids megabenthos structure exists between many polar estuarine only environmental peculiarity here was the sediment repre- zones. sented by the well-sorted sands without any clay (Table 1). All the trawl samples were characterized by the very Taking into account such sediment structure, we assume that a strong dominance of the two to four taxa. This is a typical high near-bottom turbulence occurs within that area. The situation for the zones influenced by the river runoff. turbulence should be strong enough to remove the finest Galkin et al. (2010) report that in all the previous trawl sediments from this area. There was a significant difference samplings from the Ob Bay, the two–three dominating taxa between the trawl and grab samples: the latter had numerous made up 85–99 % of the whole biomass. burrowing polychaete species and lacked actively moving The community found at station 5002 was unique, and amphipods and fishes. Perhaps all the rapidly moving organ- nothing similar was ever described from the Kara Sea. The isms were able to escape from the grab before its closure.

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The community at station 5003 corresponded with the and are able to escape from the grab before its closure. All typical ophiuroid community (O. sericeum ? O. bidentata) the small but numerous organisms like oligochaetes, some found at such depth (55 m) in the eastern part of the Arctic polychaetes (M. arctia, Tharyx sp., T. carica etc.) and Ocean (Zenkevich 1963; Antipova and Semenov 1989; bivalves (P. arctica, M. niger) could be lost from the trawl Piepenburg et al. 1996; Piepenburg and Schmid 1996). samples during the washing due to their size—the most of According to some previous studies, the O. sericeum the specimens of these species in grabs were smaller than community should occupy the territories to the south from 1 mm. Large sipunculids, some bivalves (Thyasiridae, this station, including the area of stations 5001 and 5002 Macoma calcarea, Mya truncata) and polychaetes (T. (Filatova and Zenkevich 1957; Antipova and Semenov forbesii, S. typicus) were burrowed deep in the silt and 1989). Nevertheless, not a single O. sericeum was found escaped the sigsbee trawl which was apparently cutting the elsewhere except station 5003. The role of the scallop S. upper few cm of the sediment. The grab samples included greenlandicus was surprisingly high at this station the sediments from more than 30 cm depth. Thereby the S.

(23.26 % ri). This species, typical for the O. sericeum typicus empty tubes in the trawl samples from 5003 were communities, was never recorded as the main dominant. only the upper part of the tubes cut by the trawl frame, According to the results of CCA analysis, there are three while the living worms remained deeper in the sediment. factors that influence the community structure in the The lack of the actinarians in 5002 trawl sample could be investigated area. The most significant are the salinity and explained by the sediment structure at this station—the temperature directly related with the Ob water discharge. sands with the high level of flow. Usually the trawl sample The other environmental factors influence the benthic comes aboard almost unwashed with all the sediment (clay communities far off the Ob Bay at the two northernmost or silt) and the small organisms remaining inside the trawl stations 5002 and 5003. These stations are placed sepa- net. The trawl from 5002 lacked the sediment because it rately at the CCA plot apparently due to the two factors— was washed away through the 0.5-cm net together with the sediment structure and depth (Fig. 7). actinarians and all other organisms smaller than mesh size We compared our results with the macrobenthic data of the trawl net. obtained from the grabs in the area near the Yamal pen- insula in the southwestern part of the Kara Sea (about 200 km west from the Ob Bay) where no influence of the Conclusions freshwater runoff exists (Kozlovskiy et al. 2011). Inter- estingly, the community with the dominance of the bivalve Analyses of both trawl and grab data allowed us to dis- A. borealis was found there at the depths of 20–40 m. The tinguish three different community complexes in the Ob species composition was similar to our station 5001 and Bay and adjacent shelf of the Kara Sea. These are the seemed to be identical with the A. borealis community freshwater complex located in the area of the Taz Bay described by Filatova and Zenkevich (1957) near the mouth, the brackish-water complex located in the northern mouth of the Ob Bay. Kozlovskiy et al. (2011) reported half of the Ob Bay and the marine complex located on the that the benthic communities in the southwestern part of shelf out from the Ob Bay. The southern stations of the the Kara Sea were stable during the years 1945–2007. In latter complex are more similar to each other due to the contrast to this, our data demonstrate variations of the dominance of bivalves P. arctica and isopods S. sabini and macrobenthic structure in the area of the Ob bay and S. sibirica. This correlates with the previous investigations adjacent Kara Sea shelf during the same period. carried out in the area of the Ob Bay and adjacent Kara Sea shelf. The northern two stations of the marine complex Comparison of trawl and grab data differed from the southern ones significantly. The contact area of the brackish-water and the freshwater complexes The results of the SIMPER analysis allowed us to deter- demonstrated the gradual transition between these two mine which groups appear to be best represented in trawl or complexes. That is the zone with the fluctuations of the grab samples. Crustaceans, echinoderms and some mol- salinity correlating with the temperature. These parameters lusks play the more notable role in the trawls, while the are the most important environmental factors influencing most of the polychaetes, sipunculids and bivalves are more the bottom communities along the Ob Bay. The other numerous in the grabs at the same stations (Table 6). We significant factors revealed in this study are the sediment assume that there are several reasons for that. The echi- structure and depth. noderms, large gastropods (Buccinum spp.) and some Our data allow us to assume the changes in the macro- crustaceans (isopods and decapods) are too rare to be benthos structure around the mouth of the Ob Bay. The area caught with the grab. The other crustaceans (mysids, previously reported to be occupied by the bivalve A. bore- cumaceans and amphipods) are rapidly moving organisms alis or H. arctica is now populated mainly by P. arctica. 123 Polar Biol

The presence of intense bottom perturbations caused by Rachor E (2003) The southern Kara Sea ecosystem: Phyto- water turbulence in the northern part of the investigated area plankton, zooplankton and benthos communities influenced by river run-off. In: Ruediger S (ed) Siberian River Runoff in the can provide conditions for the development of the unique Kara Sea: characterization, quantification variability and envi- community largely dominated by mobile organisms (am- ronmental significance. Proceedings in Marine Science, 6, phipods, nephtyid polychaetes and fishes). Elsevier, Amsterdam, pp 237–275 Eleftheriou A, Moore DC (2005) Macrofauna techniques. In: Acknowledgments Thanks are to the director of the Shirshov Eleftheriou A, McIntyre AD (eds) Methods for the study of Institute of Oceanology, RAS R.I. Nigmatulin for the organization of marine benthos, 3rd edn. Blackwell, Oxford, pp 160–228 R/V «Akademik Mstislav Keldysh» cruise and to the director of the Ernest MSK, Enquist BJ, Brown JH, Charnov EL, Gillooly JF, Savage Russian Research Institute of Fisheries and Oceanography «VNIRO» MV, White EP, Smith FA, Hadly EA, Haskell JP, Lyons KS, A.N. Makoedov for the organization of the tugboat «OTA-777» Maurer BA, Niklas KJ, Tiffney B (2003) Thermodynamic and cruise. We thank K.V.Minin, G.A. Koluchkina, A.A. Udalov and P.V. metabolic effects on the scaling of production and population Sapozhnikov for their help in the collection of the material. We also energy use. Ecol Lett 6:990–995 thank V.A. Chechko, P.N. Makkaveev, N.A. Belyaev and L.L. De- Filatova ZA, Zenkevich LA (1957) The quantitative distribution of mina for providing the sediment and hydrochemical data. We are the bottom fauna of the Kara Sea (in Russian). Tr Vsesoyuzn especially grateful to N.V. Kucheruk for informative discussions. 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