School of Forest Resources and Environmental Science, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA.
School of Forest Resources and Environmental Science, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA.
Sci Total Environ. 2014 May 1;479-480:66-76. doi: 10.1016/j.scitotenv.2014.01.102. Epub 2014 Feb 15.
Mercury (Hg) is a leading contaminant across U.S. water bodies, warranting concern for wildlife species that depend upon food from aquatic systems. The risk of Hg toxicity to large herbivores is little understood, even though some large herbivores consume aquatic vascular plants (macrophytes) that may hyper-accumulate Hg. We investigated whether total Hg and methylmercury (MeHg) in aquatic forage may be of concern to moose (Alces alces) and beaver (Castor canadensis) by measuring total Hg and MeHg concentrations, calculating sediment-water bioconcentration factors for macrophyte species these herbivores consume, and estimating herbivore daily Hg consumption. Abiotic factors impacting macrophyte Hg were assessed, as was the difference in Hg concentrations of macrophytes from glacial lakes and those created or expanded by beaver damming. The amount of aquatic-derived Hg that moose move from aquatic to terrestrial systems was calculated, in order to investigate the potential for movement of Hg across ecosystem compartments by large herbivores. Results indicate that the Hg exposure of generalist herbivores may be affected by macrophyte community composition more so than by many abiotic factors in the aquatic environment. Mercury concentrations varied greatly between macrophyte species, with relatively high concentrations in Utricularia vulgaris (>80 ng g(-1) in some sites), and negligible concentrations in Nuphar variegata (~6 ng g(-1)). Macrophyte total Hg concentration was correlated with water pH in predictable ways, but not with other variables generally associated with aquatic Hg concentrations, such as dissolved organic carbon. Moose estimated daily consumption of MeHg is equivalent to or below human reference levels, and far below wildlife reference levels. However, estimated beaver Hg consumption exceeds reference doses for humans, indicating the potential for sub-lethal nervous impairment. In regions of high moose density, moose may be ecologically important vectors that transfer Hg from aquatic to surrounding terrestrial systems.
汞（Hg）是美国水体中的主要污染物，这引起了人们对依赖水生系统食物的野生动物物种的关注。尽管一些大型食草动物会食用可能超积累汞的水生维管束植物（大型藻类），但它们对汞毒性的风险仍知之甚少。我们通过测量水生饲料中的总汞和甲基汞（MeHg）浓度、计算这些食草动物食用的大型藻类物种的沉积物-水生物浓缩因子，以及估算食草动物的每日汞摄入量，来研究水生饲料中的总汞和 MeHg 是否会对驼鹿（Alces alces）和海狸（Castor canadensis）造成危害。评估了影响大型藻类汞含量的非生物因素，以及来自冰川湖和海狸筑坝形成或扩大的湖泊的大型藻类汞浓度的差异。还计算了驼鹿从水生系统向陆地系统转移的水生来源汞的量，以研究大型食草动物是否可能通过生态系统隔室转移汞。结果表明，与水生环境中的许多非生物因素相比，食草动物的一般习性可能更受大型藻类群落组成的影响。大型藻类物种之间的汞浓度差异很大，其中 Utricularia vulgaris 的浓度相对较高（在一些地点超过 80ng/g），而 Nuphar variegata 的浓度可忽略不计（~6ng/g）。大型藻类总汞浓度与水的 pH 值呈可预测的相关关系，但与其他通常与水生汞浓度相关的变量无关，如溶解有机碳。估算的驼鹿每日甲基汞摄入量相当于或低于人类参考水平，远低于野生动物参考水平。然而，估算的海狸汞摄入量超过了人类的参考剂量，表明存在亚致死神经损伤的潜在风险。在驼鹿密度较高的地区，驼鹿可能是将汞从水生系统转移到周围陆地系统的重要生态媒介。
