Sublethal effects of a chlorinated and heated effluent on the physiology of the mussel, Mytilus edulis L.: a reduction in fitness for survival?

Coastal power stations entrain large volumes of cooling water, requiring biocidal treatment to prevent biological fouling. Discharged effluent is both heated and contaminated with residual traces of biocide and so it is necessary to quantify the impacts of this discharge. Cooling water from Heysham 2 nuclear power station, NW England, UK, is discharged to the intertidal area, via a culvert (to minimise erosion and maximise dilution and dispersion by directing the effluent into the receiving water at all states of the tide) within which the effluent is contained at low water. The culvert and surrounding coastal area support a population of blue mussels (Mytilus edulis). Mussel health was determined along a gradient of exposure, using three physiological indices: Scope for Growth, Gonad Mantle Index and Somatic Condition Index (K Factor). The Mussels within the culvert exhibited reduced physiological index values compared to an external site. A trend was identified down the length of the culvert, representing a gradient of exposure and indicating a potential negative effect on growth and reproductive output.

The authors are grateful to Dr. Roger F. Uglow at the University of Hull and Professor John Widdows at Plymouth Marine Laboratory for their valuable comments and assistance. The constructive and helpful remarks of an anonymous reviewer are also gratefully acknowledged as is the funding for this study provided by EDF Energy (previously Nuclear Electric plc and British Energy plc, Barnwood, Gloucestershire, UK) and their permission to publish this work. The delay in publication was due to changes in circumstances of the initial primary researcher (N.H.) and the funding body but, given the significance of the findings and their timeliness due to a resurgence in proposed building of new nuclear plants, there was a renewed impetus in completing the publication. The comments here are those of the authors and do not necessarily reflect those of EDF Energy.

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