Seasonal and annual variations of phytoplankton production in the Bering Strait region and Chukchi Sea.

Abstract

Because of the political issues and logistic problems, none of field studies has been done seasonally and annually in the whole Bering Strait and Chukchi Sea regions, although these regions are the only conduit of water masses and organic matter between the North Pacific and Arctic Oceans. Based on the in situ measurements for chlorophyll-a and primary production in 2003-2004, the seasonal and annual variations of primary production in the regions were examined from the satellite ocean color images (MODIS) during the recent period (2002-2006). The Seasonal and annual variations of chlorophyll-a concentration and production of phytoplankton were generally higher in the western side than in the eastern side of the Bering Strait region. This is corresponding to the variation of nitrate concentration measured in the Bering Strait region from 2000 to 2004, although the pattern of ammonium concentration was not same as that of nitrate. The primary production in the eastern side of the region was much higher in this study than those of in situ measurements. This is believed to the effects of inorganic particles in the water column discharged from rivers and coastal areas in Alaska. Another alternative one is the effects from suspended particles from sediments on seafloor because of a shallow water depth. The production in the central Chukchi Sea as a "hot spot" also was rather variable in different seasons based on the average production from 2002 to 2006.