Ecosystem
The Bering Sea shelf break is the dominant driver of primary productivity in the Bering Sea. This zone, where the shallower continental shelf drops off into the North Aleutians Basin is also known as the “Greenbelt”. Nutrient upwelling from the cold waters of the Aleutian basin flowing up the slope and mixing with shallower waters of the shelf provide for constant production of phytoplankton.
The second driver of productivity in the Bering Sea is seasonal sea ice that, in part, triggers the spring phytoplankton bloom. Seasonal melting of sea ice causes an influx of lower salinity water into the middle and other shelf areas, causing stratification and hydrographic effects which influence productivity. In addition to the hydrographic and productivity influence of melting sea ice, the ice itself also provides an attachment substrate for the growth of algae as well as interstitial ice algae.
Some evidence suggests that great changes to the Bering Sea ecosystem have already occurred. Warm water conditions in the summer of 1997 resulted in a massive bloom of low energy coccolithophorid phytoplankton (Stockwell et al. 2001). A long record of carbon isotopes, which is reflective of primary production trends of the Bering Sea, exists from historical samples of bowhead whale baleen. Trends in carbon isotope ratios in whale baleen samples suggest that a 30-40% decline in average seasonal primary productivity has occurred over the last 50 years. The implication is that the carrying capacity of the Bering Sea is much lower now than it has been in the past.
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