Abstract

Marine turtle are considered 'Endangered' or 'Critically Endangered' on the IUCN (World Conservation Union) Red List of Threatened Species and are listed on Appendix I in CITES. These endangered sea turtles are at risk of extinction and major factors affecting these ancient reptiles are human-related activities, such as the increased recreational use of beaches, commercial fishing, oil spills, and the unsustainable commercialization of sea turtles' meat, shells, skin, oil and eggs. The bioaccumulation of heavy metals is also responsible for the decline and depletion of sea turtle populations as well. Endangered marine turtles can absorb heavy metals from food and sea water, as well as at birth from pollution in their nesting areas. Lead is known to be carcinogenic and toxic to many types of cells including bone marrow, kidneys, muscles and the nervous system, while cadmium can cause severe toxic in fish and wild animals. Exposure to mercury compound may lead to neurotoxic and immunotoxic effects. Heavy metal suppresses immunity in some marine mammals and increases mortality of viral infected animals, and also affects the function of reproductive system. Evaluation of blood heavy metal level is considered a useful non-lethal method to monitor and predict internal heavy metal accumulation. However, there are very few studies on blood level of heavy metal in these endangered marine species, especially no data available in Thailand. Therefore, this study was aimed to investigate blood level of heavy metal Pb, Cd, and Hg using AAS as well as basic health status including physical, parasitic and blood examination in 130 captive and 18 wild sea turtles inhabiting the Gulf of Thailand and Andaman Sea. Four species of sea turtles, green turtles (Chelonia mydas), olive ridley turtles (Lepidochelys olivacea), hawksbill turtles (Erethmochelys imbricate) and loggerhead turtles (Caretta caretta), were examined from July 2006 to October 2007. Ectoparasites, principally barnacles, were found burrowing holes on all species of both captive and non-captive turtles while performing physical examination suggesting that they are possible opportunistic pathogens. Leeches were found on carapace of 3 captive hawksbill turtles in the Gulf of Thailand, however no blood parasites were detected. Trematode and nematode eggs and larvae of undetermined species were found in some fecal samples of sea turtles surveyed but infected host showed no clinical sign. Blood profiles of all turtles were in reference ranges except in some individuals showed higher creatinine which may be related to renal disorder; however, more parameter for renal function such as creatinine kinase should be evaluated for confirmation. In this study, PbB, CdB, and HgB levels were found to be the average of 1.33±0.79, 0.51±0.12, 1.70±0.90 µg/dl in captive and 2.82±1.08, 1.54±0.19, 2.05±0.95 µg/dl in wild sea turtles of the Gulf of Thailand, respectively, whereas the average were 1.13±0.65, 0.52±0.30, 2.21±1.39 µg/dl in captive and 3.92±1.94, 3.63±2.80, 1.30±1.22 µg/dl in wild sea turtles of Andaman Sea, respectively. Blood heavy metal levels were likely to be higher in wild marine turtles except for HgB concentration. There was no relationship between blood heavy metal levels and basic health status of sea turtles surveyed.