Assessment of the impact of xenobiotic pollutants on the marine organisms: Molecular biomarker approach
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The contamination of the marine environment by xenobiotic compounds such as poly aromatic hydrocarbons (PAHs), persistent organic pollutants (POPs), polychlorinated biphenyls (PCBs), organochlorine (OC) pesticides, heavy metals, tri-butyl tin (TBT) etc. through different pathways is indeed a global concern. Because of bioaccumulation of their residues into the tissues of marine organisms poses a serious threat to the health of the marine ecosystem. Once the xenobiotic contaminants get accumulated in the tissues of the marine organisms, they undergo various kinds of biotransformation through metabolic pathways such as cytochrome P-4501A1 enzyme induction leading to the formation of reactive oxygen species (ROS) which in turn form DNA adduct and eventually triggering the occurrence of DNA strand breaks. The biological responses of the marine organisms exposed to enhanced concentration of various types of xenobiotic contaminants are very useful indicator for assessment of the contamination of the marine environment inhabiting different species of organisms. The measurement of cytochrome P-4501A enzyme activity in terms of ethoxy resorufin o-deethylase (EROD) activity provides an insight into the extent of contamination of the organisms by xenobiotic pollutants as evidenced by the experiment with different species of marine fishes (Mugil cephalus, Sardinella longiceps and Rastrelliger kanagurta). On the other hand, the measurement of Glutathione-S-transferase activity indicates the exposure of the organisms to xenobiotic compounds being transformed into reactive oxygen species. Most importantly, the occurrence of DNA strand breaks in marine organisms leading to the loss of DNA integrity is a significant biomarker of marine pollution. The measurement of the DNA integrity is thus a useful tool to assess the impact of genotoxic compounds on the marine organisms which can serve as early warning signal of environmental carcinogenesis. Apart from these, the acetylcholinesterase activity (AChE) in marine gastropods (Planaxis sulcatus, Morula granulata, Nerita chameleon, etc.) provides valuable information in regard to the contamination of the marine environment by neurotoxic compounds such as organophosphorus pesticides, heavy metals (cadmium, lead, mercury, copper, chromium etc.). In order to assess the impact of various types of xenobiotic contaminants on the marine environment it is of great significance to follow an integrated approach of using asuite of biomarker.
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