Phytoplankton in the Northwestern Kara Sea I
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ISSN 00014370, Oceanology, 2015, Vol. 55, No. 4, pp. 547–560. © Pleiades Publishing, Inc., 2015. Original Russian Text © I.N. Sukhanova, M.V. Flint, E.I. Druzhkova, A.F. Sazhin, V.M. Sergeeva, 2015, published in Okeanologiya, 2015, Vol. 55, No. 4, pp. 605–619. MARINE BIOLOGY Phytoplankton in the Northwestern Kara Sea I. N. Sukhanovaa, M. V. Flinta, E. I. Druzhkovab, A. F. Sazhina, and V. M. Sergeevaa aShirshov Institute of Oceanology, Russian Academy of Sciences, Nakhimovskii pr. 36, Moscow, 117997 Russia bMurmansk Marine Biological Institute, Kola Research Center, Russian Academy of Sciences, ul. Vladimirskaya 17, Murmansk, 183010 Russia email: [email protected] Received April 24, 2014 Abstract—Studies were conducted in the northwestern Kara Sea in late September of 2007 and 2011. The assessment of species, size, structure, abundance, and biomass of phytoplankton and the role of autotrophic and heterotrophic components in phytocenoses was conducted. The abundance of autotrophic micro, nano and picoplankton increased by more than an order of magnitude in each of the following smallersized groups of algae. Microphytoplankton dominated in the total biomass of autotrophic phytoplankton. The wet biomass of microphytoplankton was 2.5 times higher than the wet biomass of nanophytoplankton and 5 times higher than that of picoplankton. Nanophytoplankton dominated in abundance and biomass in the het erotrophic component of phytoplankton. The ratio of the total abundance of autotrophic and heterotrophic phytotoplankton was 7 : 1, the ratio of the wet biomass of the both groups was 2.5 : 1, and the proportion of the carbon biomass was 2 : 1. Three biotopes were distinguished in the area of the outer shelf, the continental slope, and the deepwater area adjacent to the St. Anna Trough, which differed in composition and quantita tive characteristics of phytocenoses. Frontal zones dividing the biotopes are characterized by high phy toplankton biomass and the dominance of diatoms in the community (more than 40% of the total biomass), which indicates the local availability of “new” nutrients for planktonic algae. DOI: 10.1134/S0001437015040141 INTRODUCTION analyzed in relation to the hydrophysical and hydro chemical conditions of particular areas–biotopes. The northwestern part of the Kara Sea is the most complex region of the basin. This is the region of inter action between the waters of the Kara Sea shelf and the AREA OF STUDY, Central Arctic. The flow of the warmer and more saline MATERIALS AND METHODS waters of Atlantic origin which propagate from the The samples were collected during two cruises northwest along the western part of the St. Anna Trough aboard the RV Academician Mstislav Keldysh on Sep and the eastern Novaya Zemlya current flowing to the tember 23–25, 2007 and September 28–29, 2011. The northeast along the Kara Sea coast of the Novaya Zem studies were conducted in the outer shelf from depths lya have a considerable effect on the hydrobiological of 115–140 m, in the region of the continental slope structure and water dynamics in the region [2, 15]. The and in the St. Anna Trough with depths of 545–555 m. northern boundary of the surface lens of waters desali In 2007, 52 phytoplankton samples were collected at nated by the freshwater runoff of the Ob and Yenisei riv 9 stations along the quasimeridional transect in the ers lies in the northwestern part of the Kara Sea [1, 2]. latitude range from 75°33.3′ to 76°55.5′ N; in 2011, a The interaction of the waters of different origin forms total of 32 phytoplankton samples were collected at the system of distinct frontal zones in the region. The 8 stations along the transect between 76°17.0′ and ° ′ northwestern part of the basin is characterized by a high 76 58.4 N (Fig. 1). diversity of environmental conditions in which the Samples for phytoplankton analysis were taken planktonic community functions. Up to the present, from 5 to 3L Rosette Niskin bottles. The sampling the features of the arctic phytocenosis formed under depths were selected after the initial CTD profiling of such conditions were unknown. the vertical distribution of temperature, salinity, and chlorophyll fluorescence. Samples were collected The aim of this study is to assess the qualitative from four to six layers, which covered the upper mixed composition, abundance, size structure, biomass of layer (2–3 samples), the pycnocline and/or the layer of pelagic algae, and the contribution of autotrophic and the fluorescence maximum (1–2 samples), and the heterotrophic components of phytoplankton to the layer below the pycnocline (1–2 samples). qualitative characteristics in the northwestern Kara The phytoplankton was concentrated by a gentle Sea. The features of the phytocenosis structure were reverse filtration technique using Lavsan filters with a 547 548 SUKHANOVA et al. ° ° N (a) 4984 N (b) 5045 4983 5046 5047 4987 4986 5048 5049 4988 5050 5044 4989 5043 4990 76 76 a a ly 4991 ly 5004 em em Z Z ya ya va va o o N N 74 KARA SEA 74 KARA SEA r r e e v v Yamal i Yamal i R R Peninsula Peninsula 72 Ob 72 Ob 55 60 65 70 75° E 55 60 65 70 75° E Fig. 1. Scheme of stations in 2007 (a) and in 2011 (b). pore diameter of 1 µm. The technique was developed tionary conditions using a Leica DM 5000 lumines at the Institute of Oceanology [7]. Most samples were cent microscope at the magnification ×200–1000. processed without fixation in a living state immedi Small and numerous forms were counted in 50– ately after concentration or within one or two days 100 microscope fields of view; rare forms were after the sampling. The live samples were stored in a counted by the total examination. refrigerator at a temperature of 2–3°C. The samples Cell volumes were calculated on the basis of their were assessed in a Nojeotte counting chamber (with a size and the principle of similarity to appropriate ste volume of 0.084 mL, 400 × magnification) and a Nau reometric figures. The organic carbon content of algae mann chamber (with a volume of 1 mL, 200 × magni was estimated from their cell volumes [14]. fication) using Jena Lumar, Leica, and Biolam 2 var. 12. Phytoplankton samples were examined under light and fluorescent regimes to detect heterotrophic forms. RESULTS After processing the live material, all samples were fixed in 1% solution of neutral formalin to estimate the Species structure and a heterotrophic component of abundance of large forms of diatoms and dinoflagel the phytocene. The materials characterized the autumn lates under stationary conditions. The wetcell biom stage of phytocene succession. In the surveyed area, ass was calculated based on the principle of the geo 166 species of algae were detected in phytoplankton and metric similarity using the data from measurements of 12 forms were identified by genus. Dinophyceae (81 specie) and (Bacillariophyceae (54 species) had the their linear dimensions and volumes. The carbon con largest number of species. The other classes had less tent in the cells was calculated using appropriate coef species diversity: Cryptophyceae (8 species), Prymne ficients for different taxonomic and size groups [14, siophyceae (7 species), Prasinophyceae (4 species), 16, V.I. Vedernikov unpublished data]. Chrysophyceae (4 species), Dictyochophyceae (3 spe The data on picophytoplankton (cell diameter of cies), Euglenophyceae (1 pecies), Pedinophyceae 1–2 µm) and the smallest forms of nanoplankton (1 species), Ebriidea (1 species), Choanoflagellidae (diameter of 3–6 µm) were obtained using samples (1 species), and Siluaniacea (1 species). collected in 2011. For enumeration of pico and nan Most species were detected in the samples during oplankton, water samples were taken from the same both years of studies. The frequency of occurrence of bottles and from the same layers as the phytoplankton 47 species was more than 80% (according to the num samples. Samples for pico and nanoplankton quanti ber of stations); 63 species of algae typical for the Kara fication were prepared by staining 50 mL of water with Sea were recorded only during one year of studies. primulin, preserved in 3.6% glutaraldehyde solution They were, mainly, species recorded at 1–2 stations, and filtered through black nuclear membranes with a rarely at 3–4 stations and not numerous. Thus, in pore size of 0.4 µm [9, 12, 13] using our modification 2007, the most frequent species were Chaetoceros dia of technique [17]. Then the samples were immediately dema (occurrence at 89% of stations, maximum abun frozen and stored at –24°Cuntil analysis under sta dance 18.0 × 106 cells/m2), C. concavicornis (55%, OCEANOLOGY Vol. 55 No. 4 2015 PHYTOPLANKTON IN THE NORTHWESTERN KARA SEA 549 6.0 × 106 cells/m2), C. debilis (55%, 10.2 × 106 cells/m2), N C. decipiens (55%, 6.0 × 106 cells/m2), Eucampia 6000 graenlandica (77%, 47.2 × 106 cells/m2), and Paralia sulcata (55%, 3.2 × 106 cells/m2). In 2011, only one 1 species of diatoms, Chaetoceros tenuissimus, was 4000 numerous and frequent. The species was recorded at 87% of stations and reached the maximum abundance 2000 (7.8 × 106 cells/m2). Among Dinophyceae, 17 spe cies were recorded in 2007 and 19 species in 2011. 2 Most of these species had extremely low abundance 0 and were detected at 1–2 stations. Only three species 100806040200 of Dinophyta, Torodinium teredo, Alexandrium osten Distance along the transect, km feldii, and Protoperidinium granii reached the maxi mum abundance 0.41 × 106, 0.39 × 106, and 0.26 × St. 5045 46 47 48 49 44 43 106 cells/m2, respectively and were detected at 50% of stations in 2011. Fig. 2. Distribution of the total abundance In 2011, the taxonomic list was added to with (N × 106 cells/m2) of phytoplankton species typical for 11 autotrophic and 2 heterotrophic species of pico northern (1) and southern (2) regions of the surveyed area in the Kara Sea.