Annual primary production of phytoplankton in Lake Verkhneye,Schirmacher Oasis,Antarctica

Algal carbon 14 fixation, photosynthetically active radiation (PAR), temperature and nutrients were measured from March 1976 to January 1977 and from November 1983 to February 1984 in a small freshwater lake. As a consequence of the minute meltwater input, the PAR extinction coefficient was very low ranging between 0.04 and 0.12m^–1 throughout the year. Low extinction combined with the transparent and mostly snowless ice cover resulted in high noon PAR intensities of 640–2340 Em^–2s^–1 in the lake from November to January. As a result of the small annual total phosphorus loading (0.01 mmol m^–3 of lake), phosphate concentration in the main water mass did not exceed 0.03 mmol m^–3 during most of the growing season. Phytoplankton assimilation rates were very low with a minimum of 0.03 mgC (mgChl a)^–1 h^–1 in December. The annual net primary production was 0.58 gCm^–2, the lowest value on record. These low levels were due to photoinhibition and phosphorus limitation.