The effects of light and temperature on photosynthate partitioning in Antarctic freshwater phytoplankton

The effects of temperature and radiation flux on the partitioning of photosynthetically fixed carbon into four intracellulai metabolic pools was investigated for natural phytoplankton assemblages from an Antarctic freshwater lake. At ambient temperature, protein synthesis was saturated at low photon flux densities (30–40 μmol m −2 s −1 ) and above this flux fixed carbon was increasingly stored as lipid and polysaccharide. Increasing temperature raised both the saturated rate of protein synthesis and the photon flux at which saturation occurred. There was a corresponding decline in the accumulation of reserve products, particularly at low radiation fluxes. The consequences of this pattern of uptake for the phytoplankton is discussed.