Mercury contamination in spotted seatrout, Cynoscion nebulosus: An assessment of liver, kidney, blood, and nervous system health |
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Authors: | Douglas H Adams Christian Sonne Rune Dietz Pall S Leifsson |
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Affiliation: | a Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, 1220 Prospect Ave., No. 285, Melbourne, FL 32901, USAb Arhus University, National Environmental Research Institute, Department of Arctic Environment, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmarkc University of Michigan, Department of Environmental Health Sciences, School of Public Health, 109 S. Observatory St, Ann Arbor, MI 48109, USAd University of Copenhagen, Department of Veterinary Disease Biology, Faculty of Life Sciences, Grønnegårdsvej 15, DK-1870 Frederiksberg, Denmarke University of Copenhagen, Department of Basic Animal and Veterinary Sciences, Faculty of Life Sciences, Bülowsvej 17, DK-1870 Frederiksberg, Denmark |
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Abstract: | Marine fishes in South Florida (Florida Keys-Florida Bay-Everglades region) accumulate higher concentrations of mercury (Hg) in their tissues than similar fishes from other areas of the southeastern U.S., though it is not known whether these elevated levels affect fish health. In this study, we used quantifiable pathological and biochemical indicators to explore Hg-associated differences in marine fish from South Florida, where Hg contamination is high, and from Indian River Lagoon, Florida, which served as a reference area. Hg concentrations in all tissues of mature spotted seatrout (Cynoscion nebulosus) from South Florida were significantly higher than those from Indian River Lagoon and were within the threshold range of those in studies where effects of Hg exposure have been observed. The distribution of Hg among tissues followed the same trend in both areas, with the greatest concentration in kidney tissue, followed by liver, muscle, brain, gonad, and red blood cells. Blood-plasma biochemistry showed that concentrations of iron, inorganic phosphate, lactate dehydrogenase, and aspartate aminotransferase were significantly less in South Florida. Also, fructosamine and alkaline phosphatase were significantly less in South Florida. Liver histology revealed that pyknosis/necrosis, interstitial inflammation, and bile duct hyperplasia were found only in seatrout from South Florida, and steatosis/glycogen was more frequently found in Indian River Lagoon specimens. In renal tissue, interstitial inflammation, glomerular dilatation and thickening, and tubular degeneration and necrosis were more frequently found in South Florida specimens. Changes in the liver cytoskeleton and morphology may explain some of the differences in blood parameters between study areas. Neurochemical analyses showed that brain N-methyl-d-aspartic acid (NMDA) receptors (but not those of muscarinic cholinergic receptors, monoamine oxidase, or acetylcholinesterase) were significantly less in fish from South Florida than from Indian River Lagoon. These findings provide compelling evidence that elevated Hg could cause quantifiable pathological and biochemical changes that might influence the health of spotted seatrout and could also affect other marine fish species. |
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Keywords: | Cynoscion nebulosus Spotted seatrout Histopathological tissue changes Mercury effects Neurochemical biomarkers |
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