Trophic relations between two agents of sewage purification systems: Algae and mosquito larvae

A study of the grazing of the alga Selenastrum sp. by mosquito larvae (Culex pipiens), which are common agents in sewage purification systems, was carried out. The effect of larval excretions on the algal growth was determined, as were effects of temperatures (15–28°C), light-dark conditions, larval densities, and size and initial algal concentrations on the grazing activity. Small larvae were more active than large, and light stimulated higher activity than dark conditions. The effect of increasing larval densities and initial algal concentrations was enhancement of grazing activity. Larval excretions of P and NH₃—N enhanced algal growth slightly. A consideration of the advantages and disadvantages of the presence of mosquito larvae in sewage purification systems is presented.