Urban water ecology at the ESA annu...( Increasingly human urban development...)

Increasingly, human urban development overlaps with habitat for wild animals and plants, creating environments that degrade natural landscapes. But people, animals and plants all have in common the need for healthy, sustainable freshwater ecosystems. In a series of presentations at the Ecological Society of America's Annual Meeting, ecologists present research results that guide efforts to balance an increasingly urbanized society with the need to conserve and protect water and aquatic ecosystems.

Urban stream pollution can be good for mosquitoes

Sewage overflows are a fact of life in urban areas, and in many cities, excess sewage water enters streams and lakes with rain runoff. Although this pollution is harmful to most organisms, there is one group of insects that thrives on it: mosquitoes.

Luis Fernando Chaves, a post-doctoral researcher at Emory University, and his team discovered mosquitoes in abundance in a sewage-contaminated stream in Atlanta, but rarely in a nearby clean stream. They also found that mosquitoes were largest in streams with high levels of organic minerals in this case, nitrogen and phosphorous that originated from the sewage treatment plants. Likewise, in laboratory experiments, mosquitoes reared in sewage overflow were larger than those reared in clean water.

"In this food web, mosquitoes feed on microorganisms that require nitrogen and phosphorous to grow," Chaves says. "This translates into an input of food for the mosquitoes." When there's more organic matter, the microorganisms flourish, he says, and larval mosquitoes can eat like kings.

To make matter worse, it's possible that other aquatic insects that would feed on mosquito larvae are poisoned in sewage overflow water. Many aquatic insects breathe underwater through gill-like structures, so excess nitrogen and phosphorous could be toxic to them. Mosquito larvae, however, breathe air at the water's surface through a specialized siphon. Chave
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