Birth rate of planktonic rotifers in relation to food concentration in a shallow, eutrophic lake in western Canada

Population dynamics and birth rates of Keratella quadrata, Keratella cochlearis, Keratella earlinae, Pompholyx sulcata, and Brachionus angularis were studied in a shallow eutrophic lake of western Canada during 1975–1976. The Keratella species were collected throughout the year with maximum population densities in spring and fall. Pompholyx sulcata and B. angularis were common only during summer months.An extensive correlation analysis involving 'lagged' variables was performed to ascertain relations between birth rates and environmental parameters (temperature and food). Birth rates of all five species were positively correlated with temperature. Concentrations of certain phytoplankton (Rhabdomonas, Rhodomonas, Chlamydomonas, and Ankistrodesmus) were positively correlated with Keratella birth rates. Birth rates of K. cochlearis and P. sulcata were positively correlated with concentration of bacteria. Correlations involving 'lagged' variables were often different from those using 'simultaneous' variables.