Photosynthetic Nature and Primary Productivity of Antarctic Freshwater Phytoplankton

The standing crop of phytoplankton and photosynthetic characteristics of algal communities, together with the physico-chemical nature of water, were investigated in 9 lakes of a barren rocky area near Syowa Station (69°01′S, 39°35′E) in Antarctica. Chlorophyll-a amount ranged from 0.36 to 1.57 mg chl-a/m3 for surface water and from 52 to 121 mg chl-a/m2 for benthic algal communities. Percentage of chlorophyll a to total chlorophylls ranged from 23 to 45%. Typical shade-type photosynthesis with strong light inhibition at high light was observed both on the phytoplankton and benthic algae. Mean photosynthetic rate under light saturated condition was 0.94 mgC/chl. a mg/hr for phytoplankton and 1.2 mgC/chl. a mg/hr for benthic algae. Addition of nitrate to lake water stimulated the photosynthesis. Calculated values of daily primary production of phytoplankton and phytobenthic communities were 3.3-15mg C/m2 and 740-1480mg C/m2, respectively.