Picoplankton and nanoplankton variability in an Antarctic shallow coastal zone (Admiralty Bay) during the austral summer of 2010/2011

摘要

The distribution and variability of picoplankton and nanoplankton in Admiralty Bay (King George Island, South Shetland Islands, Antarctica) were studied by investigation of five sampling sites during the austral summer of 2010/2011. After a relatively warm winter, the water temperature in the early summer (> 0.02 A degrees C) was higher than is normal in December. The spatial-temporal variability of salinity was low, whereas water temperature and chlorophyll a increased significantly (p < 0.05) toward late summer. Nitrite and phosphate concentrations increased whereas nitrate and silicate decreased during the summer. Picoplankton increased by late summer and was dominated by heterotrophs (> 96 %), with abundance and biomass tenfold (similar to 10(9) cells L-1) and twofold (similar to 60 A mu g C L-1) higher, respectively, than were observed in previous studies. In contrast, nanoplankton was dominated by photoautotrophs (> 60 %), and values were highest in the early summer, with cell numbers (similar to 10(6) cells L-1) and biomass (similar to 90 A mu g C L-1) a factor of two lower than those found in a previous study. Temperature changes, inputs from ice melting, and grazing relationships between planktonic components seemed to have crucially important effects on the distribution patterns of these pico and nanoplankton communities. We suggest that additional study must be performed to develop a better understanding of abiotic and biotic factors that affect the abundance, biomass, and production of plankton smaller than 20 A mu m, their place in the microbial food web and the possible consequences of environmental changes on higher trophic levels in such Antarctic coastal environments as Admiralty Bay ASMA.