Life at the edge: benthic communities at the Barents Sea ice edge in a changing climate (BASICC): a Norwegian-Russian cooperative project

Figure 1. Distribution of a) zoobenthos biomass (g/m2) and b) average monthly duration of the ice edge (conditions of 20% ice cover in spring/summer) in the Barents Sea. Data calculated from PINRO zoobenthos survey in 1968-1970 and Shlitzer (2002), respectively. Figure courtesy of Stanislav Denisenko, Zoological Institute, St. Petersburg. (Click on image to enlarge)

Sea-ice is a dominant feature of Arctic ecosystems, which also are characterised by simplicity in upper trophic layers. However, on the sea-floor there are complex communities of benthic animals living on or in the sediment. In some areas, these are extremely high in biomass and/or numerical abundance.

Figure 2. The location of sampling stations in the Barents Sea examined during the BASICC cruise in August 2003.

Benthic organisms rely entirely on sedimented material for food, the amount, type and availability of which is influenced by many factors including seasonality, ice-cover, grazing by plankton and bottom currents. At the ice-edge, there is a very intense and highly seasonal surge of primary production (McRoy & Goering 1974; Grossmann & Gleitz 1997, Hegseth 1997; Makarevich 1998; Zernova et al. 2000). Although no direct link is as yet proven, patterns in benthic biomass in the Barents Sea seem to show some relationship with the extent of ice-coverage (Figure 1).

A working hypothesis may therefore be made that benthic biomass is significantly affected by ice cover. If this is the case, climate-driven changes in the extent of ice cover are likely to cause a series of changes to the sea floor biota and other animals feeding off them, including fish and certain marine mammals.

Financed by the Research Council of Norway, a joint Russian-Norwegian expedition to the Barents Sea was carried out in August 2003. A total of 49 stations were sampled (Figure 2). The main objectives were to investigate the benthic faunal communities and energy flow at the ice-edge, in seasonally ice-covered areas and in permanently ice-free areas.

The survey vessel RV Ivan Petrov in the marginal ice zone in the north-eastern Barents Sea.

Quantitative samples of benthic fauna were taken, for analysis of community composition. An inter-disciplinary approach was used to relate biological phenomena with physical and chemical characteristics of the sediments and overlying water masses. In addition, core samples were taken for analysis of sedimentation rates and bioturbation.

To trace the relative influence of food arising from ice-algae compared with phytoplankton in open waters, samples were taken of bottom-living organisms, zooplankton, phytoplankton and ice-bound material. Using stable isotopes, the aim is to trace and compare different food sources and to relate this to the composition and biomass of the benthic faunal communities in the area.

A box core was used to take sediment samples from the seabed. The depth of water ranged between 100 and 450m. Surface sediment will be analysed for a range of physical and chemical parameters. Sub-sample cores were taken from the box core sample for determination of sedimentation rates and bioturbation depths.

The research vessel used was RV Ivan Petrov, of VNIIOCEANGEOLOGIYA in Arkhangelsk, Russia. Good working relationships were formed, and our sincere thanks go to the captain and crew, as well as cruise leader Boris Vahnstein and his team for unfailing and ever-smiling round-the-clock operation of sampling equipment.

Through this project, existing cooperation between institutes were strengthened and expanded to include new participants. The project runs until 2005 and will contribute to the 6th Framework Network of Excellence MARBEF (Marine Biodiversity and Ecosystem Functioning) which is currently under negotiations with the EU. MARBEF is coordinated by Prof. Carlo Heip. Through these national and international initiatives, we hope to promote the importance of Arctic biodiversity as a significant and unique component of Europe biodiversity and to highlight the work that is being carried out in this region.

Cruise participants

Norway: Sabine Cochrane (project leader, Akvaplan-niva, Tromsø), Chris Emblow (EcoServe Ltd., Dublin), Kanchan Maiti (University of South Carolina) and Håvard Dahle (University of Oslo).

Russia: Stanislav Denisenko (Russian coordinator), Slava Potin, Andrey Voronkov (all Zoological Institute, St. Petersburg) and Alexander Frolov (Murmansk Marine Biological Institute).

A modified van Veen grab was used for sampling the benthic fauna. Five replicate samples were taken at each of the 49 stations.

Participating institutes

Akvaplan-niva (Michael Carroll, Salve Dahle), Bates College, USA (Will Ambrose), University of Troms (Paul Wassman) and the Norwegian Polar Institute (Stig Falk-Petersen).

References

Grossman S., Gleitz M. 1997. Primary and microheterotrophic productivity within ice-associated habitats. Ber.Polarforschung 226:73-79. 

Hegseth E.N. 1997. Phytoplankton of the Barents Sea - the end of growth season. Polar Biol. 17:235-241. 

Makarevich P.R. 1998. The vernal state or the microphytoplankton community in the ice-covered areas of the south-eastern Barents and the south-western Kara seas. In: Biology and oceanography of the Kara and Barents Seas (along the Northern Marine route). Apatity, KSC RAS. P.138-149. 

McRoy C.P., Goering J.J. 1974. The influence of ice on the primary productivity of the Bering Sea. In: Oceanography of the Bering Sea with emphasis on renewable resources. Proc. Int. symp., Fairbanks, Inst. Mar. Sc. Univ. Alaska. P. 403-421. 

Schlitzer R., Ocean Data View, http://www.awi-bremerhaven.de/GEO/ODV, 2002. 

Zernova V.V., Nothig E.M., Shevchenko V.P. 2000. Vertical microalgal flux in the northern Laptev Sea (from data collected by a yearlong sediment trap). Oceanology 40(6):801-808.