Lytic Organisms and Photooxidative Effects: Influence on Blue-Green Algae (Cyanobacteria) in Lake Mendota, Wisconsin

Abstract

The effects of exposure to high light intensities on blue-green algal (cyanobacterial) populations were examined in Lake Mendota, Wis. The algal populations were shown to be susceptible to inhibition of photosynthetic activity and pigment bleaching as a result of exposure. These effects generally influence only a small percentage of the lake population and thus are probably not important in causing major declines in chlorophyll a . Lytic organisms were shown to increase in numbers in the lake in response to the seasonal development of blue-green algae, reaching values of greater than 1,000 plaque-forming units per ml in midsummer. Both bacteria and protozoa were observed in plaque zones, but it could not be determined whether these lytic organisms had a major role in algal biomass declines.