Factors Influencing the Growth of Phytoplankton

In reviewing the literature dealing with the influence of physical, chemical and biochemical factors on the development and decline of phytoplankton pulses, this paper first outlines the seasonal cycle of phytoplankton pulses which occurs in many parts of North America and then presents evidence that this cycle is caused chiefly by the seasonal change in water temperatures resulting from the change in solar radiation. The way in which this cycle is sometimes obscured by irregular changes in phytoplankton numbers caused by local conditions of weather or nutrient supply is next illustrated. The climate, weather and chemical conditions are then resolved into the components light intensity, duration of illumination, temperature, concentration of nutrients, ionic balance and pH, and these are classified according to specific effects on the growth and survival of plankton algae as limiting, controlling and lethal factors. The roles of factors originating within the organisms (i.e., autotoxins and antibiotics) a...