Phytoplankton succession during a massive coastal diatom bloom at Marian Cove, King George Island, Antarctica

Abstract

To understand the community structure and the functional dynamics of phytoplankton over the long term, it is essential to identify rapid changes in the properties of Antarctic phytoplankton communities in relation to ongoing changes in environmental factors due to climate change. This study investigated short-term variability in the phytoplankton biomass and its composition over the summer of 2010 when the sea surface temperature was lowest and chlorophyll-a (chl-a) concentrations were the highest, relative to a 15-year monitoring period (1996-2011). We assessed the intraseasonal variability of the phytoplankton assemblage structure and its synchrony with changes in the main environmental variables in Marian Cove of King George Island, Antarctica. Chlorophyll-a concentrations in summer 2010 (January-February) were significantly higher (up to 24 mu g L-1) when the high phytoplankton carbon biomass (603 mu g C L-1) was dominated by the sympagic diatom Navicula glaciei, the benthic diatoms Licmophora belgicae and Fragilaria striatula, the planktonic diatoms Thalassiosira antarctica and Thalassiosira spp. (cell size <10 mu m), and the Haptophyceae nanoplanktonic cells of Phaeocystis antarctica. Intraseasonal processes such as easterly winds direction on Maxwell Bay appeared to be the main factors affecting the advection of cold, nutrient-rich waters, and water stability that enhanced phytoplankton growth in Marian Cove.