The Eastern Bering Sea shelf: a highly productive seasonally ice-covered sea

No abstracts are to be cited without prior reference to the author.

The Eastern Bering Sea is characterized by its broad (> 500km), shallow (mean depth = 70m), and seasonally ice-covered shelf. The spatial extent of ice and the timing of ice retreat are driven by large-scale atmospheric forcing and vary considerably interannually. This variability affects the spatial distribution of fish and invertebrates, the timing of the spring bloom, and the flow of energy to upper trophic levels, including shifts between benthic and pelagic compartments. High productivity on the shelf (up to 200-250 gC m-2 y-1) is fueled by nutrient-rich waters originating in the deep Aleutian Basin and supports a large community of demersal and pelagic fish and shellfish, as well as large populations of seabirds and marine mammals. Fish biomass and commercial catches (> 1.3 million tons annually) are dominated by gadids, in particular walleye pollock (Theragra chalcogramma), and flatfishes (Pleuronectidae). Although the composition of the fish community has remained relatively stable for several decades, a large-scale community reorganization affecting all trophic levels followed a 1976/77 climate regime shift. Walleye pollock currently play a key role in the food web of the Eastern Bering Sea, with much of the primary production transferred to higher trophic levels through predation on larval and juvenile pollock. The Eastern Bering Sea occupies the transition between the sub-arctic and the Arctic, which makes the region particularly sensitive to climatic change. With recent warming, the region may be undergoing a transition from Arctic to sub-arctic conditions, including a northward shift in the distribution of numerous demersal species and the emergence of newly dominant predators on commercially valuable species.