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Trace Element Concentrations in Blood and Scute Tissues from Wild and Captive Hawaiian Green Sea Turtles (Chelonia mydas).

ABSTRACT: Sea turtles are exposed to trace elements through water, sediment, and food. Exposure to these elements has been shown to decrease immune function, impair growth, and decrease reproductive output in wildlife. The present study compares trace element concentrations in green turtles in captivity at Sea Life Park Hawaii (n = 6) to wild green turtles in Kapoho Bay, Hawaii, USA (n = 5-7). Blood and scute samples were collected and analyzed for 11 elements via inductively coupled plasma-mass spectrometry (ICP-MS). Selenium was significantly greater (p < 0.05) in the blood of captive turtles compared with wild turtles, whereas V, Ni, and Pb were significantly greater in the blood of wild turtles. In scute, V, Cu, Se, and Cr were significantly greater in captive turtles, whereas As was significantly greater in wild turtles. Pelleted food fed to the captive turtles and representative samples of the wild turtle diet were analyzed via ICP-MS to calculate trophic transfer factors and daily intake values. Wild turtles had greater estimated daily intake than captive turtles for all elements except Cu and Se. Because captive turtles are fed a diet very different from that of their wild counterparts, captive turtles do not represent control or reference samples for chemical exposure studies in wild turtles. No toxic thresholds are known for sea turtles, but rehabilitation and managed care facilities should monitor sea turtle elemental concentrations to ensure the animals' health. Environ Toxicol Chem 2021;40:208-218. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

SUBMITTER: Shaw KR

PROVIDER: S-EPMC8452040 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:RationaleThe ecological application of stable isotope analysis (SIA) relies on taxa- and tissue-specific stable carbon (Δ13 C) and nitrogen (Δ15 N) isotope discrimination factors, determined with captive animals reared on known diets for sufficient time to reflect dietary isotope ratios. However, captive studies often prohibit lethal sampling, are difficult with endangered species, and reflect conditions not experienced in the wild.MethodsWe overcame these constraints and determined the Δ13 C and Δ15 N values for skin and cortical bone from green sea turtles (Chelonia mydas) that died in captivity and evaluated the utility of a mathematical approach to predict discrimination factors. Using stable carbon (δ13 C values) and nitrogen (δ15 N values) isotope ratios from captive and wild turtles, we established relationships between bone stable isotope (SI) ratios and those from skin, a non-lethally sampled tissue, to facilitate comparisons of SI ratios among studies using multiple tissues.ResultsThe mean (±SD) Δ13 C and Δ15 N values (‰) between skin and bone from captive turtles and their diet (non-lipid-extracted) were 2.3 ± 0.3 and 4.1 ± 0.4 and 2.1 ± 0.6 and 5.1 ± 1.1, respectively. The mathematically predicted Δ13 C and Δ15 N values were similar (to within 1‰) to the experimentally derived values. The mean δ15 N values from bone were higher than those from skin for captive (+1.0 ± 0.9‰) and wild (+0.8 ± 1.0‰) turtles; the mean δ13 C values from bone were lower than those from skin for wild turtles (-0.6 ± 0.9‰), but the same as for captive turtles. We used linear regression equations to describe bone vs skin relationships and create bone-to-skin isotope conversion equations.ConclusionsFor sea turtles, we provide the first (a) bone-diet SI discrimination factors, (b) comparison of SI ratios from individual-specific bone and skin, and (c) evaluation of the application of a mathematical approach to predict stable isotope discrimination factors. Our approach opens the door for future studies comparing different tissues, and relating SI ratios of captive to wild animals.

Project description:Protozoa morphologically consistent with Caryospora sp. are one of the few pathogens associated with episodic mass mortality events involving free-ranging sea turtles. Parasitism of green turtles (Chelonia mydas) by these coccidia and associated mortality was first reported in maricultured turtles in the Caribbean during the 1970s. Years later, epizootics affecting wild green turtles in Australia occurred in 1991 and 2014. The first clinical cases of Caryospora-like infections reported elsewhere in free-ranging turtles were from the southeastern US in 2012. Following these initial individual cases in this region, we documented an epizootic and mass mortality of green turtles along the Atlantic coast of southern Florida from November 2014 through April 2015 and continued to detect additional, sporadic cases in the southeastern US in subsequent years. No cases of coccidial disease were recorded in the southeastern US prior to 2012 despite clinical evaluation and necropsy of stranded sea turtles in this region since the 1980s, suggesting that the frequency of clinical coccidiosis has increased here. Moreover, we also recorded the first stranding associated with infection by a Caryospora-like organism in Hawai'i in 2018. To further characterize the coccidia, we sequenced part of the 18S ribosomal and mitochondrial cytochrome oxidase I genes of coccidia collected from 62 green turtles found in the southeastern US and from one green turtle found in Hawai'i. We also sequenced the ribosomal internal transcribed spacer regions from selected cases and compared all results with those obtained from Caryospora-like coccidia collected from green turtles found in Australia. Eight distinct genotypes were represented in green turtles from the southeastern US. One genotype predominated and was identical to that of coccidia collected from the green turtle found in Hawai'i. We also found a coccidian genotype in green turtles from Florida and Australia with identical 18S and mitochondrial sequences, and only slight inter-regional differences in the internal transcribed spacer 2. We found no evidence of geographical structuring based on phylogenetic analysis. Low genetic variability among the coccidia found in green turtle populations with minimal natural connectivity suggests recent interoceanic dissemination of these parasites, which could pose a risk to sea turtle populations.

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Trace Element Concentrations in Blood and Scute Tissues from Wild and Captive Hawaiian Green Sea Turtles (Chelonia mydas).

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