Variation of phytoplankton communities and biomass along latitude in the western Arctic Ocean

Abstract

In order to investigate a phytoplankton communities structure and carbon biomass of phytoplankton along a transect in the western Arctic Ocean, this study was carried out at 37 stations at surface and sub-chlorophyll-a maximum (SCM) depths from July 19 to September 5, 2008 in the Bering Sea, Chukchi Sea and Canadian Basin Phytoplankton communities were composed of 71 taxa representing Dinophyceae, Cryptophyceae, Bacillariophyceae, Chrysophyceae, Dictyochophyceae, Prasinophyceae and Prymneosiophyceae. The most abundant species were nano-pico sized phytoplankton at surface and SCM depths of most stations, but the second dominant species were variable among stations. In general, dominant species were Thalassiosira sp., Chaetoceros sp. and unidentified nano-pico phytoplankton such as Dinobryon belgica and Cryptomonas sp.. Nano- and pico-sized phytoplankton were tentatively dominant in the Bering Sea, whereas diatoms and nano-sized plankton were major communities in the Bering Strait and Chukchi Sea. From the western Bering Sea to the Bering Strait, the abundance and biomass of phytoplankton were getting more and species diversity was richer, but after passing through the Bering Strait they were lower and poor along latitude to the central Arctic. There were positive correlations between phytoplankton abundance and physical factors such as temperature and salinity. Although nano- and pico-sized phytoplankton were the important contributors for increasing cell abundance, their contents of Chl-a and carbon biomass were not higher than those of micro-sized cells. These results might be thought that micro-sized phytoplankton such as diatoms were main carbon producers in the western Arctic Ocean.