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October 27, 2003
Seattle, Washington, USA

Changes in Arctic Productivity: Is it Ice?

Peter McRoy¹, Rolf Gradinger², Alan Springer³, Bodil Bluhm⁴, Sara Iverson⁵, Suzanne Budge^6
1Institute of Marine science, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA, Phone 907-474-7783, Fax 907-479-2707, ffcpm@uaf.edu
²Institute of Marine Science, University of Alaska Fairbanks, PO Box 757220, Fairbanks, AK, 99775, USA, Phone 907-474-7407, Fax 907-474-7204, rgradinger@ims.uaf.edu
³Institute of Marine Science, University of Alaska Fairbanks, PO Box 757220, Fairbanks, AK, 99775, USA, Phone 907-474-6213, Fax 907-474-7204, ams@ims.uaf.edu
⁴Institute of Marine Science, University of Alaska Fairbanks, 245 O’Neil Bldg, Fairbanks, AK, 99775, USA, Phone 907-474-6332, Fax 907-474-7204, bluhm@ims.uaf.edu
⁵Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada, Phone 902-494-2566, Fax 902-494-3736, siverson@is.dal.ca
⁶Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada, Phone 902-494-2566, Fax 902-494-3736, budges@is.dal.ca

Has the carrying capacity of the western Arctic and Bering Sea declined? Using stable carbon isotope data from the baleen of bowhead whales as a proxy for food web productivity, Schell (2000) has argued that a drop of 30 to 40% has occurred over the past 5 decades. While this contention is not without challenge (e.g. Cullen et al. 2001) this remains as the accepted paradigm to account for ecological changes in the region. However, McRoy et al. (2001), using seasonal nutrient depletions on the Bering Sea shelf for the past 20 years, found no such trend in primary productivity. We measured the stable carbon isotope signatures of phytoplankton and sea ice algae in the Beaufort Sea to construct a food web mixing model with these two primary sources of carbon. The model estimates the proportion of sea ice algal carbon in the diet of the whales. Estimates range from greater than 30% to about 10% since 1945. A strong relationship exists between this trend and the extent of summer sea ice suggesting that the decline in the whale baleen isotope values is related to a shift from ice algal to phytoplankton carbon.

Abstract Categories: Changes in the Sea

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