Director of the research group “Marine end Environmental toxicology” - Sfax Preparatory Engineering Institute, Sfax, Tunisia
Marine and environmental Toxicology, ES11ES90, IPEIS, Po Box 1172- 3018-Sfax-University of Sfax, Tunisia
The marine environment is exposed to various and complex pollution from both industrial and urban effluents. The molecules generated by this pollution reach the marine environment and are susceptible to alter the physiology the reproduction of marine organisms. In order to optimise without constraints the exploitation of marine resources, one of the major challenges is to distinguish between “clean” and polluted ecosystems.
Considering the disadvantages of using sea water and sediments in pollution monitoring, marine organisms such as bivalves were shown to be successful Bioindicators of pollution. In fact, these organisms accumulate contaminants usually from water and food. The accumulation reflects only the bio-available fraction and gives us information about the health status of on considered ecosystem.
Biomonitoring programs based on measuring contaminants in marine organisms are interesting from a human health point of view. However, it does not give information about the toxicological significance of pollutants accumulated and does not indicate the health status of the organisms particularly because xenobiotics can be stored in various forms such as insoluble precipitates and concretions. Consequently, biomonitoring programs are now involving biomarkers. These are measurable parameters at different levels of biological organisation, molecular, cellular or physiological. They traduce changes in the metabolic regulatory processes resulting from the effect of anthropogenic stressors. We can detect and quantify the biochemical interactions between a contaminant and its biological receptor in the living organism. In such case we can determine pollution concentrations needed to initiate this response which is assumed to be lower than those required to provoke a life threatening situation for the organism or a degradation of the ecosystem. This early warning system response is called a biomarker. Among the long list of biomarkers proposed, we can find metallothioneins (MTs), malonedialdehyde (MDA), acetylcholinesterase (AchE), glycogen, etc… Additional tests reflecting the general health status of marine bivalves were also used such as stress on stress test and lysosomes membrane stability.
The Gulf of “Gabès » is located in the south-eastern coast of Tunisia. Shallow waters, weak currents, high salinity and temperature characterise this area. It constitutes a spawning and refuge areas for larvae’s. Nevertheless, an important industrial activity is now being developed along the coasts and could menace the aquatic ecosystem.
Two sedentary filter feeding marine bivalves satisfying criteria required for good bioindicators of pollution were used as bio monitors: Ruditapes decussatus and Cerastoderma glaucum. They are widely distributed along the Tunisian coast.
Different approaches were used: in situ, in vivo studies and on transplantation experiments. Our studies were multi parametric taking into account both biotic and abiotic factors. Some mathematical models were used to describe the relationship between pollution and the measured responses.
In the present work, measurable effects of pollution will be presented and discussed together with the relationship between toxic metal pollution and some biomarkers.