Annual and seasonal variations of phytoplankton, chlorophyll, and photosynthesis in Lake Kinneret

Annually, during the months January to June, a heavy bloom of the dinoflagellate Peri-dinium cinctum fa w&ii occurs in warm ( 13-30 ” C), monomictic Lake Kinneret, Israel. The rates of carbon assimilation, determined with ‘“C, were not exceptionally high, but algal biomass and chlorophyll concentrations measured during the bloom season were among the highest recorded for the trophogenic zone of any natural water body. Effective utiliza-tion of environmental conditions by the motile Peridinium, which dominates the phytoplank-ton assemblage and is only slightly grazed, may partly explain the large standing crops. During the bloom, physiological activities are minimal (low assimilation numbers, activity coefficients, and specific growth rates); conversely, high values for these parameters occur in late summer and fall (when Chlorophyta prcdominatc) and at the start of the bloom. The patterns of algal behavior in Lake Kinneret may have general implications for undcr-standing the role of phytoplankton in warm eutrophic ccosystcms. Of the rare studies of phytoplankton pro-ductivity in warm lakes, the most extensiv