Effects of Mosquito control Insecticides on Nitrogen Fixation and Growth of Blue-Green Algae in Natural Plankton Associations

Nitrogen (N2) fixation by blue-green algae is a significant source of fixed nitrogen for many natural and agricultural aquatic systems (FOGG et al. 1973). Laboratory studies have shown that pesticides used in aquatic habitats affect blue-green algal growth (BAT-TERTON et al. 1971; VENKATARAMAN and RAJYALAKSHMI 1972; SINGH 1973) and N2-fixation (DASILVA et al. 1975). Field studies have also shown that insecticide applications can increase biomasses of blue-green algae (RAGHU and MACRAE 1967a; HURLBERT et al. 1972) and N2-fixation rates (RAGHU and MACRAE 1967b). Since pesticides can thus affect nitrogen flow in aquatic systems, we investigated the effects of five mosquito control agents (temephos, propoxur, methoxychlor, Dimilin, and methoprene)2 on N2-fixation and growth of blue-green algae in antural plankton associations. Effects of temephos, propoxur, and methoxychlor on various algal species have previously been reported (DERBY and RUBER 1970; POORMAN 1973; KRICHER et al 1975)