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Assessment of mercury bioaccumulation in a tropical elasmobranch assemblage

Andréia Campos , Moisés Bezerra, Victor Moura, Vicente Faria, Carlos Eduardo de Rezende, Wanderley Bastos, Iuri Aparecida Oliveira, Luiz Lacerda

Abstract

Rationale Elasmobranchs widely consumed fish, making understanding Hg bioaccumulation crucial. Little is known about Hg distribution in their bodies beyond muscle tissue and the associated health risks for both animals and humans who consume them. Methodology This study evaluated Hg, MeHg, and stable isotopes (δ13C and δ15N) in the muscle, liver, and brain of 13 elasmobranch taxa landed by artisanal fisheries on the Western Equatorial Atlantic Ocean. Results The study revealed that Hg concentrations were highest in muscle tissue, while the brain exhibited the greatest percentage of MeHg. Significant correlations between Hg levels and body size, as well as between muscle and brain Hg concentrations, were observed in sharks. Stable isotope values indicated dietary and habitat diversity, and a significant correlation between Hg (log10) and δ¹⁵N was found. Mercury concentrations exceeded thresholds for harmful effects in approximately 76% of the analysed taxa and were also detected in embryos. These taxa also surpassed the local consumption limits, highlighting a potential risk. Discussion The results demonstrated bioaccumulation and biomagnification of Hg in the studied taxa. Muscle Hg was a good predictor of brain Hg levels as a result of the significant correlation between these variables. The high proportion of MeHg in the brain indicates rapid transport of Hg to this organ. Observed Hg concentrations in juveniles/adults may affect their health, while concentrations in embryos indicate possible transfer of Hg from the mother to the embryos. This study advises caution when consuming various elasmobranchs, depending on the consumer's weight and meal frequency.

EN24065  Accepted 20 November 2024

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