Ecosystem dynamics of the Pacific-influenced Northern Bering and Chukchi Seas in the Amerasian Arctic

The shallow continental shelves and slope of the Amerasian Arctic are strongly influenced by nutrient-rich Pacific waters advected over the shelves from the northern Bering Sea into the Arctic Ocean. These high-latitude shelf systems are highly productive both as the ice melts and during the open-water period. The duration and extent of seasonal sea ice, seawater temperature and water mass structure are critical controls on water column production, organic carbon cycling and pelagic–benthic coupling. Short food chains and shallow depths are characteristic of high productivity areas in this region, so changes in lower trophic levels can impact higher trophic organisms rapidly, including pelagic- and benthic-feeding marine mammals and seabirds. Subsistence harvesting of many of these animals is locally important for human consumption. The vulnerability of the ecosystem to environmental change is thought to be high, particularly as sea ice extent declines and seawater warms. In this review, we focus on ecosystem dynamics in the northern Bering and Chukchi Seas, with a more limited discussion of the adjoining Pacific-influenced eastern section of the East Siberian Sea and the western section of the Beaufort Sea. Both primary and secondary production are enhanced in specific regions that we discuss here, with the northern Bering and Chukchi Seas sustaining some of the highest water column production and benthic faunal soft-bottom biomass in the world ocean. In addition, these organic carbon-rich Pacific waters are periodically advected into low productivity regions of the nearshore northern Bering, Chukchi and Beaufort Seas off Alaska and sometimes into the East Siberian Sea, all of which have lower productivity on an annual basis. Thus, these near shore areas are intimately tied to nutrients and advected particulate organic carbon from the Pacific influenced Bering Shelf-Anadyr water. Given the short food chains and dependence of many apex predators on sea ice, recent reductions in sea ice in the Pacific-influenced sector of the Arctic have the potential to cause an ecosystem reorganization that may alter this benthic-oriented system to one more dominated by pelagic processes.