A reassessment of primary production and environmental change in the Bering Sea

Regarded as one of the world's most productive marine environments, the Bering Sea is widely thought to be rapidly warming and losing sea ice. Such changes would be expected to have dramatic impacts on primary producers, with cascading effects on upper trophic levels, including this region's vast commercial fisheries resources. Here, we use satellite-derived sea ice concentration, sea surface temperature, and ocean color data as input to a primary productivity algorithm to take stock of environmental change and primary production in the Bering Sea. Results show that, rather than declining, mean annual sea ice extent in the Bering Sea has exhibited no significant change over the satellite sea ice record (1979-2009). Furthermore, significant warming during the satellite sea surface temperature record (1982-2009) is mainly limited to the summer months, when all regions of the Bering Sea warmed. This warming suggests increasing stratification during the phytoplankton growth season. Despite certain hot spots of primary production and a strong pulse in the spring, the rate of annual area-normalized primary production in the Bering Sea (124 g C m(-2) yr(-1)) is below the global mean (140 g C m(-2) yr(-1)). Between 1998 and 2007, basin-wide annual primary production ranged from 233 to 331 Tg C yr(-1) under the influence of highly variable sea ice and temperature conditions. By comparing warm, low-ice years (2001-2005) with cold, high-ice years (1998-2000 and 2006-2007), we speculate that Bering Sea primary productivity is likely to rise under conditions of future warming and sea ice loss.