Fluctuating estuarine conditions are not confounding factors for the Comet assay assessment of DNA damage in the mussel Mytilus edulis

The Comet assay is finding increasing application as a biomarker assay for the genotoxic potential of contaminants in field transplantation experiments involving mussels. Especially in estuaries, habitats that are of particular concern,
environmental variables, such as salinity, can vary significantly. Although hinted at in the literature, there is a lack of clarification as to whether changes in salinity or emersioninduced hypoxia have the potential to alter background DNA damage in mussels, thus masking the extent of potential genotoxic effects following exposure to environmental contaminants. The present study exposed Mytilus edulis in the laboratory to static salinities (25, 50, 75, and 100 %) for 72 h. Mussels were also subjected to simulated tidal cycles, including periods of emersion, for 72 h. None of these treatments resulted in a significant change in the level of DNA damage expressed as % tail DNA. These experiments demonstrate that salinity, within the limits of the concentrations tested, and temporary emersion are not confounding factors for Comet assay data derived from M. edulis.