Soulen Brianne K, Adams Douglas H, Roberts Aaron P
Department of Biological Sciences and Advanced Environmental Research Institute, University of North Texas, Denton, TX, USA.
Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, Indian River Field Lab, Melbourne, FL, USA.
Ecotoxicology. 2019 Apr;28(3):251-260. doi: 10.1007/s10646-018-02014-w. Epub 2019 Feb 13.
Mercury (Hg) deposited into aquatic sediments can be converted into the more toxic methylmercury (MeHg) by microbial activity. Atlantic stingrays (Hypanus sabinus) are an estuarine and nearshore species found in coastal regions of the western North Atlantic, occurring in multiple habitat types, and feeding mainly on benthic invertebrates. Mercury dynamics and speciation in stingrays have not been well examined. This study quantified total Hg and Hg species (Hg (II) and MeHg) in Atlantic stingrays sampled from Florida's Indian River Lagoon (IRL) from 2012 to 2013. Tissues (muscle and liver) collected from 29 stingrays were lyophilized and homogenized before being analyzed using a direct mercury analyzer. Concentrations of total Hg in muscle were positively related to stingray disk width, but concentrations in liver were not. Mean (±SD) total Hg in muscle (0.56 ± 0.30 mg/kg dw) was significantly higher than mean total Hg in liver (0.23 ± 0.19 mg/kg dw). Within liver tissue, percent MeHg (of total Hg) ranged from 31 to 99%. The ratio between total Hg in liver and total Hg in muscle was <1 for nearly all individuals, suggesting a lack of active hepatic demethylation and sequestration mechanisms. Concentrations of Hg in IRL Atlantic stingrays fall below concentrations known to result in direct toxicity to fishes; however, effects thresholds are not well understood for elasmobranchs. Comparisons of Hg concentrations in IRL Atlantic stingrays sampled previously (37 individuals in 1994) indicate that total Hg concentrations in muscle of Atlantic stingrays have decreased over the past two decades, suggesting a reduction in the bioavailable Hg in the IRL ecosystem.
沉积在水生沉积物中的汞（Hg）可通过微生物活动转化为毒性更强的甲基汞（MeHg）。大西洋黄貂鱼（Hypanus sabinus）是一种河口和近岸物种，分布于北大西洋西部沿海地区，生活在多种栖息地类型中，主要以底栖无脊椎动物为食。黄貂鱼体内汞的动态变化和形态尚未得到充分研究。本研究对2012年至2013年从佛罗里达州印第安河泻湖（IRL）采集的大西洋黄貂鱼中的总汞和汞形态（Hg（II）和MeHg）进行了量化。从29条黄貂鱼身上采集的组织（肌肉和肝脏）在使用直接测汞仪进行分析之前，先进行冷冻干燥和匀浆处理。肌肉中总汞的浓度与黄貂鱼的盘宽呈正相关，但肝脏中的浓度则不然。肌肉中总汞的平均（±标准差）含量（0.56±0.30毫克/千克干重）显著高于肝脏中总汞的平均含量（0.23±0.19毫克/千克干重）。在肝脏组织中，甲基汞（占总汞的百分比）范围为31%至99%。几乎所有个体肝脏中总汞与肌肉中总汞的比值均小于1，这表明缺乏活跃的肝脏去甲基化和螯合机制。IRL大西洋黄貂鱼体内的汞浓度低于已知会对鱼类产生直接毒性的浓度；然而，对于软骨鱼类的影响阈值尚不清楚。对之前（1994年的37条个体）在IRL采集的大西洋黄貂鱼体内汞浓度的比较表明，在过去二十年中，大西洋黄貂鱼肌肉中的总汞浓度有所下降，这表明IRL生态系统中生物可利用汞有所减少。
