Altered gill morphology in benthic macroinvertebrates from mercury enriched streams in the Neversink Reservoir Watershed, New York.

Aquatic macroinvertebrates were collected from five sites in the Neversink Reservoir Watershed in Sullivan County, New York: Aden Brook, Biscuit Brook, Main Branch, Tison and Winnisook, and examined for gill abnormalities. The Neversink Reservoir is part of the New York City water supply system and is located in the Catskill Mountains. Total mercury and methylmercury concentrations were measured by the New York State Department of Environmental Conservation (NYSDEC) in composite samples of macroinvertebrates at the five sites and ranged from 13.