INFLUENCE OF THE ST-LAWRENCE-ISLAND POLYNYA UPON THE BERING SEA BENTHOS

The influence of a polynya, a persistent ice-free region, on water col umn production and subsequent transport to the shallow continental she lf benthos of the Bering Sea was evaluated by studying spatial pattern s of organic material deposition, benthic biomass, community sediment metabolism, benthic population structure, and other potential indicato rs of enhanced organic carbon transport to benthic communities underly ing the St. Lawrence Island Polynya. Despite suggestions that polynyas may be important localized centers of primary production in polar wat ers, we found that the St. Lawrence Island Polynya does not obviously enhance the biomass of benthic communities directly below the polynya. However, southward flowing, baroclinic currents generated as a result of brine injection at the polynya edge do appear to have an influence on the biomass and ecological structure of Bering Sea benthic communi ties south of St. Lawrence Island. These currents appear to affect mea n sediment oxygen consumption, surface organic carbon/nitrogen ratios, total organic content, and bottom water ammonia by sweeping phytodetr ital matter south and to the west of the island. A particle-reactive, short-lived, natural radioisotope, Be-7, used as an indicator of rapid (days to weeks) deposition of particulate material from the water col umn, was detected only in surface sediments to the southwest of the is land, indicating enhancement of particle deposition to the southwest o f the island. Finally, the O-18 content of tunicate cellulose was high est in the polynya region, consistent with increased filter feeding in the late winter when the polynya is present, and presumably promoting primary production in the open water. The Anadyr Current, consisting of nutrient-rich, deeper Bering Sea water that is upwelled onto the sh elf in the Gulf of Anadyr, flows west to east in the region south of S t. Lawrence Island throughout the year and is the major forcing functi on for high production in the region. The interaction of Anadyr Water with the winter/spring ephemeral polynya and associated baroclinic cur rents combine to positively influence benthic communities.