Departamento de Ecología y Evolución, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400, Montevideo Uruguay; Departamento de Ecología y Gestión Ambiental, Centro Universitario Región Este, Universidad de la República, Cachimba del Rey y Aparicio Saravia, 20000, Maldonado, Uruguay.
Departamento de Ecología y Gestión Ambiental, Centro Universitario Región Este, Universidad de la República, Cachimba del Rey y Aparicio Saravia, 20000, Maldonado, Uruguay.
Environ Pollut. 2024 Nov 15;361:124804. doi: 10.1016/j.envpol.2024.124804. Epub 2024 Aug 23.
Mercury, a toxic metal released by various human activities, exerts environmental stress through its bioaccumulation and biomagnification, particularly in marine habitats. South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) reproduce on the Atlantic coast of Uruguay. As top predators, they can accumulate toxic levels of mercury and are often used as sentinel species for monitoring ecosystem health. Fur seals prey on pelagic species, such as fish and squid, while sea lions consume coastal-benthic prey. We analyzed the total mercury concentration (THg) in hair and the trophic habits (δC and δN) of females from both species. The average THg concentration in adult female sea lions (30.5 ± 9.3 μg/g dry weight) was significantly higher than in fur seals (6.3 ± 2.5 μg/g dry weight). Additionally, the mean δN and δC values were significantly higher in sea lion (δN: 19.2 ± 0.6‰, δC: -13.8 ± 0.2‰) compared to fur seals (δN: 16.5 ± 0.5‰, δC: -15.5 ± 0.6‰). Our results suggest that different trophic levels and feedings areas affect the THg concentration in Uruguayan Otariids. Notably, at the intraspecific level, the THg concentration in sea lions increased with δC values, suggesting a link to coastal feeding habits. This indicates that coastal feeding behaviors, compared to feeding in pelagic environments, enhance mercury bioaccumulation in Otariids along the Uruguayan coast, with the discharge of freshwater from the Río de la Plata (one of the largest estuaries in South America) basin identified as a potential mercury source. THg concentrations found in female sea lion hair are the highest reported in Otariids globally. Mercury levels exceeded toxic thresholds observed in other mammals and could pose significant health risks. Our findings may explain why sea lions were particularly affected by the avian influenza outbreak in Uruguay compared to fur seals. Monitoring the declining sea lion population is crucial, making our results significant for integrated conservation and management strategies.
汞是一种由各种人类活动释放的有毒金属，通过其生物积累和生物放大作用对环境施加压力，尤其是在海洋生境中。南美海狗（Arctocephalus australis）和海狮（Otaria flavescens）在乌拉圭的大西洋海岸繁殖。作为顶级掠食者，它们可能会积累到有毒水平的汞，并且经常被用作监测生态系统健康的指示物种。海狗以鱼类和鱿鱼等远洋物种为食，而海狮则以沿海底栖猎物为食。我们分析了两种物种的雌性毛发中的总汞浓度（THg）和营养习惯（δC 和 δN）。成年雌性海狮的平均 THg 浓度（30.5 ± 9.3μg/g 干重）明显高于海狗（6.3 ± 2.5μg/g 干重）。此外，海狮的平均 δN 和 δC 值明显高于海狗（δN：19.2 ± 0.6‰，δC：-13.8 ± 0.2‰）。我们的研究结果表明，不同的营养水平和摄食区域影响乌拉圭 Otariids 中的 THg 浓度。值得注意的是，在种内水平上，海狮的 THg 浓度随着 δC 值的增加而增加，这表明与沿海摄食习惯有关。这表明与在远洋环境中摄食相比，沿海摄食行为会增强 Otariids 在乌拉圭沿海的汞生物积累，而拉普拉塔河（南美洲最大的河口之一）流域的淡水排放被认为是汞的潜在来源。在海狮毛发中发现的 THg 浓度是全球 Otariids 中报道的最高浓度。汞水平超过了在其他哺乳动物中观察到的毒性阈值，可能会带来重大的健康风险。我们的研究结果可能解释了为什么与海狗相比，海狮在乌拉圭的禽流感爆发中受到的影响特别大。监测海狮种群的减少是至关重要的，这使得我们的研究结果对综合保护和管理策略具有重要意义。
