Analysis of thermal effects on macroinvertebrate populations in the lower Vernon Pool of the Connecticut River

Gonyaw, Alex A.
Rachel Thiet, PhD
Department of Environmental Studies
This study summarizes the surface water temperatures and macroinvertebrate community present in Vernon Pool of the Connecticut River. On a broader scale, this study operates within the framework presented by Vannote et al. (1980) taking into account the functional feeding group of the various taxa observed and the impacts of environmental change on macroinvertebrate niches and broad life history types present within the Connecticut River. Vernon Pool is an impoundment formed by Vernon Dam, a 25 megawatt electric generating facility on the Connecticut River. Vermont Yankee Nuclear Power Station utilizes water drawn from the reservoir to cool its boiling water reactor and then releases it to the river. Exposure and control stations utilizing multiplate samplers and automatic recording temperature thermistors were utilized to collect synchronous temperature and macroinvertebrate data. A total of 7,087 macroinvertebrates were identified from artificial substrate samples and 298,721 temperature measurements were taken in the Vernon Pool during the summer and fall of 2002. Non-parametric tests revealed few significant differences between control stations and those exposed to the thermal plume of the Vermont Yankee Nuclear Power Station. Temperature and macroinvertebrate community variability between stations appeared to be a function of the predominant hydrologic regime and water depth of each station rather than degree of exposure to the thermal plume. Macroinvertebrate colonization potential and the variety of niches the ecosystem supported appeared to be independent of thermal plume exposure.

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