Tynan, C. T.. JISAO - Univ. of Washington, tynan@afsc.noaa.gov
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The summer distributions of migratory baleen whales typically reflect the productivity of their environments and indicate regions of high biomass of their principal prey (euphausiids and copepods). Redistributions of baleen whales, from the shelf edge during the whaling era to the middle shelf during recent years, suggest that the pathway of carbon flow has changed over the southeast Bering Sea shelf. During the 1970s, the food web of the middle shelf was a primarily benthic system, in which most of the primary production was largely ungrazed and sank to the sea floor of the central shelf. The abundance of pelagic grazers was low and the benthic biomass was high during this period. Conversely, the outer shelf domain was characterized as a more pelagic food web. The presence of high densities of foraging baleen whales on the middle shelf during the late-1990s indicates that the middle shelf has shifted to a more pelagic domain, where high secondary biomass is capable of supporting high whale biomass. This shift to a more pelagic food web, with incorporation of biomass into large whales, suggests an increase in the channeling of biogenic carbon towards pools of long-lived organic carbon. Other signals of large change in the shelf ecosystem include the occurrence of extensive coccolithophore blooms during 1997 and 1998. Given that temperature can strongly alter community structure and function, it is important to determine whether warming on the shelf over the past two decades has contributed to a shift from a primarily benthic to a more pelagic system. In view of the climate model predictions and recently observed trends in arctic climate, we should examine whether similar shifts in shelf ecosystems are occurring in other subpolar seas as a consequence of global warming.
Day: Monday, Feb. 1
Time: 02:45 - 03:00pm
Location: Hilton of Santa Fe
Code: SS14MO0245H