Potential effects of heavy metals on health of north Adriatic sea cetaceans

Marine mammals have proved to be important bioindicators for the medium-long term changes in environments due to their relatively long life and the position on the top of the food chains. The large amount of adipose tissue they possess represents an accumulation compartment for different persistent contaminants. When lipids are re-mobilised, i.e. during cold periods and pregnancy/lactation or following stressing episodes, contaminants can re-enter blood circulation, thus causing secondary intoxication or inducing pathological alterations. Despite huge literature available on contaminants determination and quantification in different cetacean species, little is known about the pathogenic or pathological effects these levels can induce. No specific reference toxicity threshold exists, and thresholds defined for other mammalian (terrestrial) species are generally used. Cytotoxicity reports concerning in vitro cetacean cells culture, anyway, seem to be in agreement with these threshold. Most dangerous chemicals are those little or no biodegraded, thus persisting for a long time in the environment and concentrating at various ecosystem levels. These chemicals include heavy metals and metalloids, i.e. mercury, lead, cadmium, copper, arsenic, chromium and nickel, and the great family of organochlorine compounds, i.e. insecticides, dioxins and PCBs. In present work we report about results obtained from the analysis of tissues of 10 stranded Tursiops truncatus, one Physeter macrocephalus and one Grampus griseus collected in Northern Adriatic Sea. Concerning T3 and T4 quantification, a comparison of data obtained from the same subjects and from different species collected by Haifa University is also presented. Obtained results allowed the definition of body burden level in cetaceans of Northern Adriatic Sea and to evaluate possible toxic effects induced by these levels, with a certain attention to immune system. It was possible to consider that at least in 4 out of 10 dolphins some lymphocytic toxicity, increase in apoptosis, reduction in lymphocytic activity and proliferation could occur, thus inducing a higher sensitivity to infectious diseases in affected animals. Thyroid hormones have also been quantified in the tissues of the two cetaceans population (Northen Adriatic and Israel). Obtained data are to be considered as innovative as regards applied method and species considered.