ISSN 00014370, Oceanology, 2015, Vol. 55, No. 4, pp. 657–659. © Pleiades Publishing, Inc., 2015. Original Russian Text © M.V. Flint, S.G. Poyarkov, 2015, published in Okeanologiya, 2015, Vol. 55, No. 4, pp. 723–726. INFORMATION Comprehensive Research on the Kara Sea Ecosystem (128th Cruise of Research Vessel Professor Shtokman) M. V. Flint and S. G. Poyarkov Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow email: [email protected] Received November 12, 2014 DOI: 10.1134/S0001437015040074 The Kara Sea is a key Arctic region, the study of account the current climatic condition of the Arctic which allows us to address not only localbasin region; related but also general regional problems. The Kara ⎯to assess the specifics of physical, hydrochemi Sea receives about 45% of the total freshwater runoff cal, biological, and geochemical processes near a large to the Arctic (1200 km2). River runoff strongly fresh desalinated surface lens formed by the runoff of the Ob ens the surface sea layer, which significantly affects and Yenisei rivers and its role in forming biological intrabasinal water exchange processes, vertical water production, as well as in the transformation and cross column mixing, nturient regimes, and thus environ shelf transfer of substances; mental conditions for. Freshwater flow carries out ⎯to study the zonal specifics of physical, hydro over 150 million tons of allochthonous materials to the chemical, biological, and geochemical phenomena and Arctic shelf, including a wide range of contaminants. processes in the eastern, practically unstudied, and the The Kara region is strongly influenced by the cli coldest and most icebound region of the Kara Sea; matic processes characteristic of the Arctic over the ⎯to investigate the hydrophysical, hydrochemical, past decades, primarily, summer icecover degrada biological, and geochemical phenomena and pro tion. On the shelf and in the coastal area, major gas cesses associated with the Ob estuarine frontal zone; to condensate and oil reserves have been explored, and determine conditions of the formation and structure their development and transportation threaten the of the plankton “biological filter” associated with the Kara ecosystem with very strong anthropogenic estuarine frontal zone, as well as its role in the trans effects. Very large radioactive burial grounds in the formation and flows of organic matter; and bays of the eastern coast of Novaya Zemlya and in ⎯to obtain hydrophysical and hydrochemical data, Novozemel’skaya Vpadina (Novaya Zemlya Trough) as well as biological materials for the characterization of have made the Kara Sea a focus of colossal accumu pelagic and benthic ecosystems in large radioactive lated ecological risks. burial grounds: the bays of the eastern coast of Novaya To study the above problems, the Oceanology Zemlya (Abrosimova, Stepovogo, Tsivol’ki, and Bla Institute RAS organized a Kara Sea expedition: the gopoluchiya) and the Novaya Zemlya Trough. 128th scientific cruise of the R/V Professor Shtok The figure shows the route of the expedition. Study man. The voyage was conducted from August 8 to revealed the location of a surface lens freshened by the September 11, 2014. The leader of the expedition was Ob and Yenisei runoff in the central and southwestern M.V. Flint, Dr. Sci. (Biol.) and deputy director of the parts of the Kara Sea. In the center of the lens, with Institute of Oceanology RAS (IO RAS); the vessel coordinates ~73°20, 20′ N and 65°40.0′ E, an area was was under the command of master mariner found with a salinity of 9.2 psu, which is a record A.A. Khromov. The expedition continued the IO RAS breaking low for the open parts of the Kara Sea. A rigid comprehensive studies of the Kara basin conducted pycnocline, with salinity gradients up to 5.5– in 2007, 2011, and 2013 and was based on the same 6.0 psu/m, underlay the freshened lens at the surface, multidisciplinary methodological approach, which hindering windinduced mixing, the flow of nutrients made it possible to combine multiyear research data. into the euphotic layer, and the seasonal descent of the lower boundary of the upper mixed layer. Data on The main goals of the expedition studies were the localization and gradient characteristics of the frontal following: zones on the periphery of the freshened lens on the ⎯to obtain the characteristics of the current state surface were obtained using continuous recording of of key abiotic and biotic components of pelagic and hydrophysical and biophysical parameters of the sur benthic ecosystems of the Kara Sea, taking into face sea layer. The boundary of the freshwater region 657 658 FLINT, POYARKOV °N 80 Voronin 12844 Trough 79 43 42 St. Anna Trough ice boundary 78 41 –100 40 39 38 37 T 36 ra 35 77 n se ct 34 V 12845 I 0 33 10 76 – yaB l 12846 32 12831 em 12812 Z 100 ya 11 – va 75 12816 No 10 KARA SEA III 09 C t c e Transect II s 74 08 n a r T T r 13 14 15 a 30 n 07 24 s e 29 73 c 23 t Transect V 06 28 I 22 S 20 27 0 05 21 Y 26 Taimyr Peninsula 0 19 12825 e 1 n 17 Transect IV i 72 – 69 se A 04 12818 i R . – 70 1 0 12803 71 71 0 Yamal 02 Peninsula . R 72 st.12801 b 70 12873 O 55 60 65 70 75 80 85 90 °E Route plan, position of transects and stations of the 128th cruise of the R/V Professor Shtokman. (<24 psu) reached the coast of the northern island of zone within the Ob estuary was practically unexpressed. Novaya Zemlya. Surface waters with the lowest salinity This was the consequence of an intensive (August) run were characterized by relatively high fluorescence val off and the effect of southward offshore winds. ues of dissolved organic matter and chlorophyll. Over The position and intensity in the salinity and tem all, the desalinated region was significantly shifted to perature field of the frontal zone over the continental the west of the basin compared to our observations of slope in the St. Anna Trough, which separates the rel 2007, 2011, and 2013. atively warm lowsalinity waters of the Kara Shelf The Ob estuarine frontal zone was characterized by from the cold and saline Arctic waters, were identical the sharply expressed southern periphery (gradients to those recorded during our studies of 2007 and 0.8–1.0 psu/km) in nearbottom salinity distribution, 2011, which made it possible to confirm the stability which lay between 72°12′ and 72°27′ N. In the northern of this important ecological boundary. periphery of the estuarine frontal zone (73°20′ N), The assessments of hydrochemical parameters in nearbottom salinity reached >33 psu, which is charac various sea areas showed that the contents of oxygen teristic of the Kara shelf. Salinity changes in the estua and main nutrients did not go beyond the limits of rine zone’s surface water layers were much more even. average multiyear values for the summer season. Phos For 220 km (from 71°12′ to 74°00′ N), salinity phate and nitrate–nitrogen concentrations in the increased from 0 to 12 psu. Surface salinity reached val euphotic layer did not drop to the analytical zero ues characteristic of the Kara shelf only at 74°50′ N; everywhere, and their concentrations could not serve thus, the external periphery of the estuarine frontal as a factor limiting phytoplankton development. OCEANOLOGY Vol. 55 No. 4 2015 COMPREHENSIVE RESEARCH ON THE KARA SEA ECOSYSTEM 659 The primary production of the Kara Sea was mea obtained for the first time for the Kara Sea. Mass zoop sured in situ for the first time in waters with various lankton species from various biotopes of the Kara Sea trophic statuses during the active period of the sea were collected, and this will allow us to assess the sonal succession of phytoplankton (August) in situ, genetic distances of populations different in their origin. which allows us to calculate the total values of primary Studies on benthic fauna made it possible to distin production in the water column. Characteristic guish a successive latitudinal change in biocoenoses dependences of the assimilation number on underwa that corresponded to the pattern given in the work by ter irradiance in waters of various optical types and Z.A. Filatova and L.A. Zenkevich based on the 1945 productivity were obtained. For the first time, the spa materials. This indicates the large temporal stability of tial variability of the lightcurve parameters of the the structure of benthic biocoenoses in the western Kara Sea phytoplankton’s photosynthesis was studied part of the Kara basin, where the largest licensed sites the maximum assimilation number, photosynthesis for shelf hydrocarbon production are located. efficiency, light saturation levels (photoadaptation parameter), optimal illuminance, and light inhibition We have obtained samples of benthic sediments, of photosynthesis. zoobenthos, and zooplankton that will make it possible Phytoplankton bloom was detected only in the to measure mercury contents in components of the southern periphery of the estuarine front (freshwater Kara Sea ecosystem and to determine mercury bioac phytoplankton, 4 g/m3) and in the central part of the cumulation ratios and transfer mechanisms. The mate freshened surface lens of waters in the western part of rials were collected to assess the radiation condition of the basin (marine types of phytoplankton, 500 mg/m3). benthic sediments in various regions of the Kara Sea, In the eastern regions of the sea near the seasonal ice including the Ob and Yenisei estuaries. edge and in the northern regions (north of 78° N), Hydrophysical, hydrochemical, and biooceano despite recent ice melting, the phytocene was at a late logical studies of Blagopoluchiya, Tsivol’ki, Stepo winter stage of seasonal succession and was character vogo, and Abrosimova bays of the Novaya Zemlya ized by a very low level of biomass, <100 mg/m3.