PHOTOSYNTHESIS-IRRADIANCE RELATIONSHIPS IN NATURAL PHYTOPLANKTON POPULATIONS OF THE BARENTS SEA

An analysis is made of the photosynthesis-irradiance relationships in natural phytoplankton populations in thc Barents Sea. The data set comprises 232 experiments carried out during a 10-year period, both in open and ice-covered waters. Thc variability on thc P-I parameters is discussed and examined in relation to thc variation in a variety of environmental conditions. The results suggest that in the Barents Sea, as in other Arctic areas, phytoplankton photosynthesis is mainly controlled by physical variables. However, control of the phytoplankton stock, i.e. by zooplankton grazing, seems also to have a considerable indirect influence on P-I parameters. especially after the spring bloom and the depletion of winter nutrients.