Microalgal communities living in melt ponds on sea ice in the Arctic Ocean

Abstract

As a Chinese IPY event, the 3rd Chinese National Arctic Research Expedition (CHINARE) was conducted from the Chukchi Sea to the central Arctic Ocean from late July to early September in 2008. During the cruise period, we measured productivities of micro algal community in 11 melt ponds in the central Arctic Ocean. Two types of melt ponds could be visually distinguished by their colors (Gradinger 2002). The productivity of the algae in melting ponds ranged from 0.01 to 0.34 mg C m-3 h-1 (average ± S.D.= 0.09 ± 0.11 mg C m-3 h-1) which were somewhat higher than those of phytoplankton (average ± S.D.= 0.07 ± 0.06 mg C m-3 h-1) at surface water in the Arctic Ocean over 80o N. Small (nano and pico cell sizes) unidentified flagellates mostly dominated the phytoplankton communities in both waters. Based on their shapes and sizes, we believe that nano unidentified flagellates in bottom closed ponds were Chlamydomonas nivalis , which is common on ice floes and melt ponds in the central Arctic Ocean (Gradinger and N&uuml

rnberg 1996). Dinobryon belgica was the second dominant species at water surface and in bottom open ponds. In contrast, Pyramimonas sp. was secondly dominant in two of the closed ponds. Overall, there were more diverse species of phytoplankton in surface water than melt ponds. Current and ongoing climate changes such as a sea ice decrease are expected to impact largely on this unique habitat in the melting ponds.