EFFECTS OF POWER-PLANT OPERATION 



ON THE LITTORAL BENTHOS 



OF BELEWS LAKE, NORTH CAROLINA 



DAVID R. LENAT 



Department of Environmental Sciences and Engineering, 



University of North Carolina, Chapel Hill, North Carolina 



ABSTRACT 



The littoral benthos of Belews Lake in North Carolina, a 1500-ha cooling 

 reservoir for a 2200-MW coal-fired power plant, was studied over a 3-year period, 

 one preoperational year and two postoperational years. Comparing control areas 

 with heated areas allowed separation of normal successional changes from 

 changes associated with power-plant operation. Twenty-four taxa were analyzed 

 in detail, and ten taxa appeared to be directly or indirectly affected by 

 power-plant operation. The densities of Polypedilum digitifer, Nais communis, 

 and Hyalella azteca decreased with increases in temperature. Densities of two 

 other taxa, Hexagenia munda and Limnodrihis hoffmeisteri, increased with slight 

 increases in temperature but decreased after further increases. Six other taxa 

 appeared to have been indirectly affected by power-plant operation through 

 changes in littoral macrophytes, periphyton, or other factors. Use of percent 

 similarity coefficients showed that the imposition of a thermal gradient resulted 

 in a corresponding "biological" gradient. 



The effects of power-plant operation on aquatic environments have 

 been frequently studied during the last decade. The impact of 

 thermal effluents is still in question, hov^ever. Many studies suffer 

 from a lack of preoperational data and /or inadequate controls, and 

 others deal w^ith environments having multiple pollutants; this makes 

 it difficult to study only the impact of powder-plant operation. The 

 study design for this investigation attempted to minimize these 

 problems. 



Studies at Belew^s Lake, North Carolina, have dealt with chemical 

 and physical parameters, phytoplankton, zooplankton, and both 



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