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Bioaccumulation of marine contaminants

Various land-based industrial, mining, domestic and agricultural activities have been identified as the main sources of priority marine pollutants in coastal waters. Toxic pollutants derived from such activities are known to contaminate marine food chains and can have appreciable impact on sensitive ecosystems and food resources in coastal areas. The use of radionuclides, radiotracers and radiolabelled organic compounds offer unique tools for investigating and understanding the behaviour and fate of these toxic substances (e.g., toxic heavy metals, PCBs and pesticides) in key temperate and tropical coastal ecosystems. This is particularly important in regions where seafood and fish are a major part of the local diet and coral reef ecosystems are sensitive to pollutant impacts.

Radiotracer techniques are most efficient in providing information on bioavailability, fate and effects of environmentally-important contaminants originating from land-based sources, using advantageous, non-destructive techniques. It is a major tool to identify uptake and retention mechanisms in marine biota in order to select and validate valuable bioindicators species to be used for coastal zone management (e.g. in monitoring programmes). It is also a very powerful approach to identify the susceptibility of economically important species (fish and other sea foods) to contamination by organic (pesticides, PCBs, oils) or inorganic (heavy metals, radionuclides) marine pollutants. In particular, investigation of contaminant bioaccumulation and retention rates, using high efficiency gamma spectrometry counting could be a very valuable tool in the selection of species for fish farming. These techniques also offer the possibility to measure different chemical forms of a given pollutant with high sensitivity (e.g. organic and inorganic mercury or tin), which may be of crucial importance in some estuarine and marine environments (e.g. those exposed to gold mining activities).

Major advantages of radiotracer techniques over conventional techniques are their very high sensitivity and discrimination capacity, that permits the measurement of bioaccumulation kinetics of several contaminants at realistic (viz. low) environmental concentrations in a single experiment. Furthermore, most heavy metals are investigated using gamma spectrometry that permits the non-destructive analyses of contaminant levels in living organisms.