The atypical seasonality of phytoplankton in Crose Mere, 1972: an independent test of the hypothesis that variability in the physical environment regulates community dynamics and structure

Abstract

Unusual features of the seasonal periodicity of phytoplankton in Crose Mere, 1972, included the extended phase of vernal diatom dominance, the development of spring populations of Pediastrum and Closterium, a large June maximum of Eudorina and a large August maximum of Volvox. With respect to temperature, thermal stability and light availability in the water column, the specific growth responses detected in 1972 are shown to be strongly consistent with those in other years and in other lakes, yet the interspecific differences are preserved. The atypical seasonality of plankton observed in 1972 was brought about by the atypical sequence of atmospheric conditions that, in turn, modified the temporal phasing and subsequent stability of thermal stratification. These events demonstrate the importance of phytoplankton responses to physical variability of the environment.