Factors Influencing the Growth of Phytoplankton

Abstract

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) are also considered. The discussion of laboratory investigations leads to certain criticisms of present culture methods and to some reinterpretation of observations obtained in some of these investigations. Finally, this paper illustrates the phenomenon of acclimation as it applies to phytoplankton, and it stresses the need for adequate prehistories of culture stocks in order that the results of different investigations can be validly compared.