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- Title
Mercury and Selenium Accumulation in the Tissues of Stranded Bottlenose Dolphins (Tursiops truncatus) in Northeast Florida, 2013–2021.
- Authors
Bielmyer-Fraser, Gretchen K.; Courville, Julia M.; Ward, Ashlen; Hardie, Mckenna M.
- Abstract
Simple Summary: Mercury is a persistent and toxic metal that can affect marine life. Bottlenose dolphins are particularly vulnerable to mercury accumulation and toxicity because they are top predators and often inhabit near-shore environments with elevated mercury concentrations. This research assessed mercury accumulation in the tissues of bottlenose dolphins that were stranded during two time periods, 2013–2015 (dolphins that were stranded at an unusually high rate; heavily infected with morbillivirus) and 2016–2021 (dolphins that were stranded at a normal rate). We hypothesized that the immunosuppressed individuals would have higher mercury concentrations. Tissue selenium accumulation was also measured, as selenium has been shown to reduce mercury toxicity. Differences in tissue mercury concentrations were not observed between the two time periods; however, the tissue mercury concentrations were higher in adults than juveniles. The selenium distribution in the bottlenose dolphins was significantly different between the two time periods. These results suggest that selenium may not have been as protective against mercury toxicity in the bottlenose dolphins that were stranded during the UME. Bottlenose dolphins (Tursiops truncatus) are long-lived marine mammals, upper-level predators, and they inhabit near-shore environments, which increases their exposure to pollution. Mercury is a ubiquitous and persistent metal pollutant that can bioaccumulate and biomagnify up the food chain. Dolphins are known to accumulate mercury, and limited research has shown that mercury exposure can weaken the immune system of dolphins. The objectives of this study were to assess the mercury concentrations in the tissues (muscle, small intestine, liver) of stranded bottlenose dolphins and to compare the tissue mercury levels in dolphins that were stranded during the 2013–2015 morbillivirus Unusual Mortality Event (UME; immunosuppressed individuals) with the levels of those that were stranded at a normal rate (2016–2021). Selenium has been shown to reduce mercury toxicity in many animals; therefore, tissue selenium concentration and the molar ratio of selenium to mercury were also assessed. The tissue mercury (muscle, liver) and selenium (liver) concentrations increased with the age of the dolphins, with the liver accumulating the highest concentrations. No sex differences were observed in the mercury and selenium concentrations. While differences in tissue mercury concentrations were not observed due to the UME, the selenium accumulation profiles were significantly different between the two time periods. These results suggest that selenium may not have been as protective against mercury toxicity in the bottlenose dolphins that were stranded during the UME, possibly due to infection with morbillivirus.
- Subjects
FLORIDA; BOTTLENOSE dolphin; SELENIUM; MERCURY; MARINE biology; MERCURY poisoning; MARINE mammals; HEAVY metals
- Publication
Animals (2076-2615), 2024, Vol 14, Issue 11, p1571
- ISSN
2076-2615
- Publication type
Article
- DOI
10.3390/ani14111571