Ecology and management of mosquitoes in constructed wastewater treatment wetlands
Woolford, Samuel Whitefield
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Throughout the world, the release of untreated or partially treated wastewater into natural basins is common practice; this has significant effects on ecosystem function, nutrient transport, microbial evolution, pathogen transmission, and human health. Constructed wetlands are an attractive wastewater treatment option for some communities and institutions because of relatively low construction and maintenance costs, additional social benefits, and potential conservation advantages over other treatment methods. Wastewater treatment wetlands are also often excellent habitat for immature aquatic-stage mosquitoes. Because of the economic incentive to build these wetlands close to human populations, municipal treatment wetlands can become a source of nuisance pests and disease vectors in the communities they serve. Immature mosquitoes were present in all but one of 19 municipal treatment wetlands sampled in Georgia, and showed a strong preference for habitats characterized by emergent aquatic macrophytes. Container experiments indicated that mosquito production is increased in partially treated wastewater and in emergent macrophytes, but that the two habitat characteristics may not have a multiplicative effect on mosquito abundance. In vegetated areas, exclusion of Gambusia affinis (Mosquitofish) suggested the fish were far more effective predators of larval mosquitoes in sections with lowest stem density. Mesocosm experiments showed that another fish native to the southeast, Heterandria formosa (Least Killifish), may be an effective predator of mosquito larvae in densely vegetated habitats. These results have strong design and maintenance implications for integrated mosquito management in treatment wetlands.