Organochlorine compounds in sea turtle blood: possible immunosupressive effect?

Degradation of marine and nesting habitats due to environmental pollution have a dramatic impact on marine turtle populations. A wide variety of synthetic organochlorine compounds (OCs) such as polychlorinated biphenyls (PCBs), and organochlorine pesticides have a particular significance in the ecotoxicology because of their undesirable effects on environmental quality and animal health. These lipophilic pollutants tend to biomagnify up the food chain and consequently, higher trophic animals in aquatic food webs have been the subject of prior concern. In fact, several reports exist in the literature about the levels of these contaminants in different aquatic Mediterranean species such as, dolphins, monk seals, sharks, tunas and swordfish. In these organisms, exposure to such pollutants has been shown to affect a variety of biological parameters with the most prominent toxic effects being on the immune, endocrine, developmental and reproductive systems. However, only a few studies have been dedicated to marine turtles, and little is known about the consequences of exposure of organochlorine compounds to sea turtles. In any case, different studies about the biological actions exerted by OCs seem to indicate that organochlorine pesticides and PCBs are capable to alter a number of biological functions in aquatic species, such as alter enzymatic pathways or induce immune suppression. Progress towards the understanding of the possible OCs impact on turtle health might be obtained with more data on accumulation of these compounds within their body and their potential relationship with morphological or physiological parameters. In this perspective the present study determined the concentrations of polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB) and organochlorine pesticides (dichlorodiphenyl-trichloroethane-derivatives -DDTs-, hexachlrocyclohexane-isomers –HCHs-, cyclodienes and endosulfan) in serum samples from specimens of turtles (C. caretta) from the Adriatic Sea and evaluated the possibility that OCs serum levels could be related with the development of the turtles (length or width of the carapace). This work reinforces the findings found for other researchers in the sense that Mediterranean turtles present a relatively high degree of contamination by organochlorines. Due to the lipophilic character of these compounds we found a positive association between the size of the turtle and the level of some organochlorines in serum. However it has drawn our attention the fact that PCB 189 was negatively associated with the thickness of the carapace, pointing to the possibility that this PCB congener could influence negatively in the growth and development of the animal.