Assessment of mercury and selenium concentrations in captive bottlenose dolphin's (Tursiops truncatus) diet fish, blood, and tissue

• Published in: The Science of the total environment Vol. 414; no. 1; pp. 220 - 226
• Main Authors: Hong, Yong Seok, Hunter, Sue, Clayton, Leigh A., Rifkin, Erik, Bouwer, Edward J.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2012
• Subjects: Animals; Animals, Zoo; aquariums; atmospheric deposition; Blood; blood sampling; Bottle-Nosed Dolphin - blood; Bottle-Nosed Dolphin - metabolism; Bottlenose dolphin; Cetacea; Deposition; Diet; Diet fish; Diets; Dolphins; Environmental Monitoring - statistics & numerical data; Environmental Pollutants - blood; Environmental Pollutants - metabolism; Fish; Fishes - metabolism; Marine; Mercury; Mercury - blood; Mercury - metabolism; Methylmercury Compounds - blood; Methylmercury Compounds - metabolism; neurotoxicity; Populations; Selenium; Selenium Compounds - blood; Selenium Compounds - metabolism; Toxicity; Tursiops truncatus; Whole blood; USA, South Carolina; USA, Maryland, Baltimore; USA, Florida; Whole blood; Bottlenose dolphin; Selenium; Toxicity; Mercury; Diet fish
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2011.11.021

Concentrations of total mercury (Hg) and selenium (Se) were determined in diet fish and whole blood and tissue samples from seven bottlenose dolphins (Tursiops truncatus) housed at the National Aquarium Baltimore (NAB). In addition, concentrations of monomethylmercury (CH3Hg+) were determined in diet fish and dolphins' tissue samples. The data were compared with the values found in wild populations to better understand how the dietary Hg and Se uptake rates affect the Hg and Se levels in dolphins. The diet fish total Hg concentrations ranged between 14 and 47ngg−1 and were markedly lower than for similar fish found in Florida, South Carolina, and other aquaria. CH3Hg+ accounted for 85 to 91% of the total Hg found in diet fish. The diet fish Se concentrations ranged between 270 and 800ngg−1, indicating excess molar concentrations of Se over Hg. The Hg concentration range in the blood of NAB dolphins was 27–117ngg−1 and the concentrations were about one order of magnitude and several factors lower than the concentrations found in the blood of wild bottlenose dolphins in Florida and in South Carolina, respectively. The total Hg and CH3Hg+ in tissue samples were also significantly lower than the reported values obtained from wild populations of bottlenose dolphins. The differences in the Hg concentrations in the dolphins' blood may be due to the different levels of Hg atmospheric deposition in the area where the dolphins' diet fish were found. The Se concentration range in the blood of NAB dolphins was 221–297ngg−1 which was two factors lower than the values found in wild populations. The lower Hg levels, as well as higher Se:Hg molar ratios in the blood of NAB dolphins, suggest that NAB dolphins may be less susceptible to the potential neurotoxicity from the CH3Hg+ in their blood. ► Captive dolphins ingest less Hg from their diet compared to those in wild dolphins. ► Captive dolphins have lower blood Hg levels than those in wild dolphins. ► Higher Se:Hg molar ratios were observed in the blood of captive dolphins. ► Captive dolphins may be less susceptible to the potential toxicity from the CH3Hg+.