Ecosystem Responses Of The Southeastern Bering Sea To Abnormal Weather Patterns In 1997 And 1998

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

Climate change will influence marine ecosystems through changes in weather patterns. Thus, examination of the interactions between weather and physical/biological processes in the ocean provides information relevant for predicting the potential impacts of global change on regional ecosystems. In response to unusual weather patterns in both 1997 and 1998, the physical and biological regimes of the southeastern Bering Sea differed greatly from long-term climatological patterns. In 1997, there was ice present until April, an ice-related bloom with draw-down of nutrients, and a mixing event in mid-May that renewed production. Unusually warm, calm weather􀀹nd deep depletion of nutrients followed. Subsequently the first-documented Bering Sea coccolithophorid bloom and a short-tailed shearwater (Puffinus tenuirostris) die-off occurred. In 1998, sea ice was present briefly in February, and.storms following ice retreat prevented a strong thermocline until late June. Rather than a short pulse, production was moderate and consistent from May through June. The coccolithophorid bloom was still present, apparently having over-wintered. Although shearwaters were again malnourished, no unusual mortality was found. In both 1997 and 1998, adult euphausiids (Thysanoessa raschil), a primary food of shearwaters, had densities over the inner shelf one to two orders of magnitude lower than in the period 1972-1982; copepod densities were one to two orders of magnitude higher than previously reported.