Fourier Transformation Analysis of Stress Biomarkers in Mussels Exposed To Lethal Municipal Effluents

The release of municipal waste waters into the environment could threaten the health and maintenance of populations of organisms living in the vicinity of urban areas.The purpose of this study was to examine the toxicity of municipal waste waters to fresh water mussels based on the biomarker responses involved in oxidative stress and genotoxicity.Elliptio complanata mussels were placed in cages and immersed in two different terminal aeration ponds treating domestic waste waters and at one river reference site for up to 48 days.Mussels were collected at different times (0, 12, 24 and 48 days) and analyzed for the following biomarkers: metallothioneins (MT), total peroxidase (Perox) activity, lipid peroxidation (LPO) and DNA damage (DD).The waste water from the first aeration pond was lethally toxic, causing 45% mortality, and the second waste water was less toxic, causing 20% mortality, after 48 days.The data revealed that most of the above biomarkers were initially induced at 12 or 24 days but the response declined afterwards as mortality was manifested in mussels exposed to the waste waters.These cyclic changes were analyzed by Fourier transform which showed that MT, LPO, Perox biomarkers produced amplitude changes at frequencies higher than those observed for reference mussels.Phase analysis revealed that these frequencies were not in phase with those of the reference mussels, which suggests heterogeneous responses or the appearance of toxicity-related frequencies that seemingly did not occur in control mussels.The number of out of phased frequencies was also higher in mussels exposed to the most toxic (lethal) waste waters compared to the least toxic waste water.Moreover, some of these frequencies occurred at similar frequencies with MT, Perox and LPO in the most toxic waste waters, suggesting that resonant signals could contribute to toxicity in fresh water mussels.In conclusion, the cyclic properties of biomarkers could provide new insights into the adverse effects on mussel health and survival.