Effect of pesticides on microbial communities in container aquatic habitats

Mosquitoes develop in a variety of aquatic habitats and feed on microbial communities associated with decaying organic matter. These aquatic habitats are often embedded within and around agricultural lands and are frequently exposed to agricultural chemicals. We used a microcosm approach to examine the single and combined effects of two herbicides (atrazine and glyphosate), and three insecticides (malathion, carbaryl, and permethrin) on microbial communities of a typical mosquito aquatic habitat. MiSeq sequencing of the V4 region of both bacterial and archaeal 16S rRNA gene was used to characterize the microbial communities of indoor microcosms that were either exposed to each pesticide alone, a mix of herbicides, a mix of insecticides, or a mix of all five insecticides. Individual insecticides but not herbicides reduced the microbial diversity and richness and two insecticides, carbaryl and permethrin, also altered the microbial community structure. A mixture of herbicides had no effect on microbial diversity or structure but a mixture of insecticides or all five pesticides reduced microbial diversity and altered the community structure. These findings suggest that exposure of aquatic ecosystems to low concentrations of pesticides can disrupt the resident microbial communities and there is need to decipher how these changes may affect mosquito growth, survival, and the risk of mosquito-borne disease.