Heavy metal content in cetaceans stranded at West and North Coasts of Sabah, Malaysia

• Main Author: Chen, Chiau Yu
• Format: Thesis
• Language: English; English
• Published: 2017
• Subjects: QL700-739.8 Mammals
• Online Access: https://eprints.ums.edu.my/id/eprint/38218/1/ABSTRACT.pdf; https://eprints.ums.edu.my/id/eprint/38218/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/38218/

A number of cetacean strandings has been reported in Sabah, Malaysia in the recent years. However, limited investigation has been done to further examine the phenomenon, hence leading to little understanding of the local cetaceans. Heavy metals, including methylmercury (MeHg) are globally-concerned pollutants. This is mainly due to their chemical properties and ability to interact with systemic enzymes, as well as their effects on cellular functions. When the body tolerance limit for heavy metal is exceeded, it can lead to dysfunction of body systems which subsequently reduce the cetaceans' fitness to survive. This inspired the current study which is the first attempt in Malaysia to examine and establish baseline concentrations of heavy metals in stranded cetaceans. Concentrations and distribution of Cd, Cr, As, Pb, Cu, Mn, Fe, Se, and Zn in the main organs (liver, kidney, heart, lung, muscle, melon, and blubber) of five cetaceans (two shortfinned pilot whale, two finless porpoises and a spinner dolphin) stranded at the west and north coasts of Sabah in 2015 were examined. MeHg in the brains were also measured as it is a neurotoxin and behavioural teratogen which mainly targets the central nervous system. None of the heavy metals was found to exceed the tolerance limit in the five cetaceans. The calf, adolescent and adult cetaceans examined in this study exhibited different manners of heavy metal distribution due to their diet and age differences. However, similar pattern of distribution was observed regardless of species variation. Concentrations of Cu, Zn, Fe, and Mn in the liver and kidney were found to be not affected by species or age. Selective accumulation of Cd was found in the kidney of adolescent short-finned pilot whale and spinner dolphin (98.65 μg g-1 dwt and 35.04 μg g-1 dwt or 54.28% and 67.13% respectively). Meanwhile, As and Cd in the finless porpoise calf were significantly (p<0.05) higher in the muscle as compared to other tissues (3.52 μg g-1 dwt and 3. 79 μg g-1 dwt) which could be due to redistribution of harmful heavy metals to protect the main organs from toxicity. Concentrations of MeHg in the brains of the four cetaceans were also examined. The MeHg concentration was found to be significantly higher (p<0.05) in the brain of the adult spinner dolphin (0. 91 μg g-1 dwt) than in other younger cetaceans (0.27 - 0.35 μg g-1 dwt). Nonetheless, it was relatively low as compared to cetaceans stranded in the temperate regions. On the contrary, brain MeHg percentage was significantly lower (p<0.05) in the adult spinner dolphin but higher in other young cetaceans (62.92 - 72.09%). This finding was similar to those of other studies which stated that demethylation activity is more efficient in adult cetaceans. Since only five cetaceans were obtained in 2015, it is suggested that such investigation efforts should be continued to properly assess the hazard of heavy metals in Sabah waters.