Department of Marine Biology, Roger Williams University, One Old Ferry Road, Bristol, RI 02809, USA.
Arch Environ Contam Toxicol. 2010 Feb;58(2):431-43. doi: 10.1007/s00244-009-9423-7. Epub 2009 Dec 9.
The summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus support valuable fisheries along the northeastern United States. The importance of these flatfish as a human dietary resource indicates they are potential sources of mercury (Hg) to fish-consuming citizens. In this study, summer flounder (SF) and winter flounder (WF) were collected from the Narragansett Bay (Rhode Island, USA) and were measured for total Hg burden in whole-body or dorsal muscle tissue. Interspecies differences in Hg contamination were analyzed relative to flounder body size, age, and Hg content of preferred prey. Stable isotope signatures were also used to elucidate the effect of trophic processes on Hg accumulation in the estuarine food web. The mean Hg content of SF exceeded concentrations measured in WF across multiple life-history stages (0.039-0.100 and 0.016-0.029 mg Hg/kg wet weight for SF and WF, respectively), and observed values for both species were lower than the US Environmental Protection Agency regulatory threshold of 0.3 mg Hg/kg wet weight. Total Hg concentrations were also positively correlated with flounder age and length, verifying that both flatfish bioaccumulate Hg. SF accumulate Hg at an accelerated rate, however, owing to this species consuming Hg-enriched prey (teleosts, squid, and macrocrustaceans; mean Hg content = 0.023 mg Hg/kg wet weight), whereas WF feed on prey with low Hg levels (amphipods and polychaetes; mean Hg content = 0.013 mg Hg/kg wet weight). The positive correlation observed between mean biota Hg content and stable nitrogen (delta(15)N) isotope signatures further indicates that Hg is trophically transferred through the food web, and higher trophic level organisms (i.e., enriched delta(15)N) have increased Hg concentrations. Therefore, results from this study suggest that dietary preference and trophic structure are the main factors affecting Hg bioaccumulation in the estuary. Total Hg concentrations of flatfish from the Narragansett Bay, however, do not necessarily reflect coastwide contamination patterns. This reinforces the importance of having research conducted at sufficiently small spatial scales, including the local assessment of Hg contamination for the purpose of issuing state consumption advisories.
夏鲆（Paralichthys dentatus）和美洲拟庸鲽（Pseudopleuronectes americanus）是美国东北部有价值的渔业鱼类。这些比目鱼作为人类饮食资源的重要性表明它们是食用鱼类的汞（Hg）潜在来源。在这项研究中，夏鲆（SF）和美洲拟庸鲽（WF）从纳拉甘塞特湾（美国罗德岛州）采集，并测量了其全鱼体或背部肌肉组织中的总 Hg 含量。根据比目鱼的体型、年龄和首选猎物的 Hg 含量，分析了种间 Hg 污染的差异。稳定同位素特征也被用来阐明营养过程对河口食物网中 Hg 积累的影响。SF 的平均 Hg 含量超过了 WF 在多个生命史阶段测量的浓度（SF 为 0.039-0.100mg Hg/kg 湿重，WF 为 0.016-0.029mg Hg/kg 湿重），并且这两个物种的观察值都低于美国环境保护署规定的 0.3mg Hg/kg 湿重的监管阈值。总 Hg 浓度与比目鱼的年龄和长度呈正相关，这证实了两种比目鱼都能积累 Hg。然而，SF 以更快的速度积累 Hg，这是因为该物种摄食富含 Hg 的猎物（硬骨鱼、鱿鱼和大型甲壳类动物；平均 Hg 含量=0.023mg Hg/kg 湿重），而 WF 则以 Hg 含量低的猎物为食（端足类和多毛类动物；平均 Hg 含量=0.013mg Hg/kg 湿重）。生物体内 Hg 含量与稳定氮（δ15N）同位素特征之间的正相关关系进一步表明，Hg 是通过食物网进行营养转移的，营养水平较高的生物（即富集的 δ15N）的 Hg 浓度增加。因此，这项研究的结果表明，饮食偏好和营养结构是影响河口比目鱼体内 Hg 积累的主要因素。然而，纳拉甘塞特湾比目鱼的总 Hg 浓度并不一定反映整个沿海地区的污染模式。这再次强调了在足够小的空间尺度上进行研究的重要性，包括对 Hg 污染的本地评估，以发布州消费建议。
