Biochemical biomarkers in juvenile Solea senegalensis for assessment of marine ecosystem health

The increasing human pressure along coastal areas has created a non negligible anthropogenic pressure on the surrounding marine ecosystem. Human originated contaminants can appear diluted in the estuarine and marine waters or accumulate in the sediments. Among other sources of stress, this contaminant input is known to reach and affect the marine biota. Marine pollution monitoring programs are developed to assess and survey status and trends of the affected aquatic environments. They are based on both chemical characterization of the ecosystem and biological effect assessment. The biological effect assessment uses some representative species for each ecosystem and is commonly analyzed by biomarker approach. Flatfish, amongst which the sole is common in the Bay of Biscay, are recognized as sentinel species in pollution monitoring programs. The application of biomarkers in marine pollution monitoring programs is recognized by international intergovernmental institutions (ICES/OSPAR, UNEP…). In the present study, juvenile Solea sp. were used to assess the potential biochemical responses to different contaminated scenarios. Farmed animals were exposed to either contaminated sediments or to a model metal (Cadmium) or to a model organic pollutant (Benzo(a)pyrene) diluted in water. Wild animals were also used to provide first data of biochemical biomarkers for Solea sp. in the Bay of Biscay. A battery of biochemical biomarkers were assessed in samples of sole liver and brain of all individuals: Acetylcholinesterase, Catalase, Glutathione S-Transferase and Superoxide dismutase). Individuals exposed to contaminated sediments showed clear inhibition or induction patterns of enzymatic activity after 28 days of exposure. Individuals exposed to diluted contaminants were also characterized by changes in the enzymatic activities showing a correlation with the contaminant concentrations or with the period of exposure (up to 21 days). The present laboratory experiments permitted to confirm the responsiveness of biochemical biomarkers to different types and levels of contaminants. It also provides significant information about the potential of Solea sp. as sentinel species for the assessment of general health status of the biota based on biochemical biomarkers. The analysis of enzymatic activities from wild animals permitted to advance in the knowledge of soles as potential sentinel species in biomonitoring programs. However, further studies are needed and better adapted sampling conditions seem to be necessary for the case of biochemical analysis.