Relationships between biochemical and physiological biomarkers responses measured on juvenile marine fish under environmental chemical contamination
Résumé
Several biomarkers have been developed and described in the scientific literature and some of them may be used to assess the quality of the aquatic environment. However, in most cases, a single biomarker can hardly be used as an early signal exposure to contaminants and report the health status of organisms. The aim of our study was to develop a multibiomarker approach on juvenile marine fish (3-4 months) in order to evaluate the biological effects of chemical pollution at different levels of biological organization. Biochemical detoxification parameters (EROD, GST) and an antioxidant enzyme (CAT) were used as early warning tools of toxicity. In parallel, juvenile fish growth and health were analyzed by the measurement of different physiological biomarkers (somatic and recent growth, RNA:DNA ratio, morphometric and lipid indices). Sensitivity and relevance of biochemical and physiological biomarkers were tested on juvenile: i) sea bass exposed to acute petroleum pollution, ii) sea bass and turbot exposed to harbour and estuarine sediments during controlled and semi-controlled (caging) conditions. Throughout all experiments, responses of biochemical biomarkers were recorded as soon as a few days of exposure which confirm their use as an early warning tool of toxicity. EROD and GST were found to be sensitive to short exposure (2 and 4 days) of organisms to petroleum. However, when fish were exposed to harbour and estuarine sediments, biochemical biomarker responses were poorly correlated with the level of metal and PAH concentrations. On the contrary, juvenile growth and condition indices were found to be more sensitive to the different levels of contaminants analysed suggesting their potentiality to reflect deleterious effects of chemical contaminants on juvenile fish health. Therefore, this study supports the use of both biochemical and physiological biomarkers in biomonitoring programs to display a more comprehensive and integrative assessment of environmental quality.