Effects of Mercury on Wildlife: A Comprehensive Review

Abstract

Wildlife may be exposed to mercury (Hg) and methylmercury (MeHg) from a variety of environmental sources, including mine tailings, industrial effluent, agricultural drainwater, impoundments, and atmospheric deposition from electric power generation. Terrestrial and aquatic wildlife may be at risk from exposure to waterborne Hg and MeHg. The transformation of inorganic Hg by anaerobic sediment microorganisms in the water column produces MeHg, which bioaccumulates at successive trophic levels in the food chain. If high trophic level feeders, such as piscivorous birds and mammals, ingest sufficient MeHg in prey and drinking water, Hg toxicoses, including damage to nervous, excretory and reproductive systems, result. Currently accepted no observed adverse effect levels (NOAELs) for waterborne Hg in wildlife have been developed from the piscivorous model in which most dietary Hg is in the methyl form. Such model are not applicable to omnivores, insectivores, and other potentially affected groups, and have not incorpotated data from other important matrices, such as eggs and muscle. The purpose of this paper is to present a comprehensive review of the Hg literature as it relates to effects on wildlife, including previously understudied groups. We present a critique of the current state of knowledge about effects of Hg on wildlife as an aid to identifying missing information and to planning research needed for conducting a complete assessment of Hg risks to wildlife. This review summarizes the toxicity of Hg to birds and mammals, the mechanisms of Hg toxicity, the measurement of Hg in biota, and interpretation of residue data.

Predictors and immunological correlates of sublethal mercury exposure in vampire bats

“…Relationships between Hg exposure and innate immunity were observed at very low THg concentrations, whereas negative health effects of Hg have been primarily observed at toxicity thresholds of 10 mg kg −1 [16,81] or subclinical thresholds of 5 mg kg −1 [72,82]. For example, such concentrations impaired cellular immunity in zebra finches ( Taeniopygia guttata [83]) and black-footed albatross ( Phoebastria nigripes [84]).…”

Hair and bone as predictors of tissular mercury concentration in the Western Alaska Red Fox, Vulpes vulpes

“…Mercury methylation occurs in aquatic environments and MeHg + is absorbed mainly from the gastrointestinal tract of some organisms and then distributes to and accumulates in some organs, including muscle, kidney, liver, and the brain (Bilandzic et al 2010; Castoldi et al 2001; Clarkson 1997; Cybulski et al 2009; Davis et al 1994; Dehn et al 2006; Graeme and Pollack 1998; Lopez-Artiguez et al 1995; Millan et al 2008; Wren 1986). In contrast to MeHg+, elemental Hg is poorly absorbed by the gastrointestinal tract (Wolfe et al 1998, Wiener et al 2003) but may be methylated in the rumen of herbivores, absorbed and redistributed (Duffy et al 2005, Lokken et al 2009). …”

Mercury in tropical and subtropical coastal environments

“…The most common organic form of Hg, methylmercury (MeHg), is of particular concern because it is a potent neurotoxin and biomagnifies in aquatic food webs. Thus, it becomes concentrated in the tissues of higher trophic level organisms (Wolfe et al, 1998). From a toxicological point of view, the key process that facilitates mercury entrance in coastal food webs is mercury methylation.…”