Winter population dynamics of Daphnia Pulex in sewage oxidation ponds

This study was undertaken to trace the seasonal changes of a Daphnia pulex population in two adjoining sewage oxidation ponds at Canning N.S. (latitude 45°N) between October 1976 and January 1977. Daphnia pulex is abundant seasonally in these ponds. In the autumn months a reproductive shift occurred from non-ephippial to ephippial egg production before adults disappeared from the water column. The population apparently overwinters as ephippial eggs. No males were found at any time during the study.