Population dynamics of Daphnia Pulex in an oxidation pond system

Population dynamics of Daphnia pulex inhabiting a sewage Stabilization system at Canning, Nova Scotia, were studied from May to September 1975 inclusive. The first oxidation pond contained diluted but untreated domestic waste water. The second received partially treated waste from the first and discharged it into Habitant Creek. Ephippia were produced in early June and again in September although males were not collected. Subitaneous egg production occurred throughout the study. Three major density peaks were observed in the Lagoon 1 with a maximum of 932 liter⁻¹ during mid-June. Densities were much lower in Lagoon 11 with one major peak of 327 liter⁻¹ in early June. The study showed density and brood size to be essentially food-limited within the system. However, because of the artificial nature of the habitat, fluctuations in oxygen or other chemical constituents may precipitate sudden large mortalities in Daphnia.