Factors That Control Species Numbers in Silver Springs, Florida1

The effect of productivity on species variety has been studied by counts of diatom species on glass slides at a high production and a low production station within Silver Springs. Species variety has been presented in a measure that is apparently independent of sample size. This measure is based on the linear increase of accumulated species with logarithmic increase of individuals counted. Diatom productivity was measured by the rate of chlorophyll accumulation. The poor station accumulated diatoms and chlorophyll slowly and was characterized by a large species variety during most of the experiment. The rich station accumulated diatoms and chlorophyll rapidly and was characterized by a rapid decrease in species variety as the density of the population increased. These results indicated that species variety was decreased by conditions of high productivity, possibly through the action of high densities and coactions. In addition, other factors that affect species variety were classified and discussed.