The effects of methylmercury on wildlife. Evers, D. Technical Report Penobscot River Mercury Study, Biodiversity Research Institute, 2012.
abstract   bibtex   
Published findings indicate that reasonable effects concentrations can be developed for certain taxa, forage guilds, and tissue types that provide replicable and scalable endpoints for assessing risk. The effects of mercury (Hg) on wildlife from 162 studies (n=98 for birds and n=64 for mammals) can generally be grouped under five categories: physiology, neurology, behavior, reproductive, and survival. Studies were differentiated between laboratory, captive, or experimentally manipulated efforts vs. studies of free-living populations. Recent findings demonstrate that (1) available methylmercury (MeHg) can significantly affect the reproductive success for wild populations of birds and mammals, (2) piscivores are at great risk, but invertivores are often times at equal or even at greater risk, especially those taxa associated with prey from wetland habitats, and (3) bird species (and likely mammals) have at least a 11 fold difference in their sensitivity to MeHg toxicity. Changes from the traditional use of point estimates such as lowest observed effect levels to the use of specific effects concentrations (EC) provides a higher resolution approach for assessing risk. The EC level of interest for decision makers should consider the demographics and conservation status of the target species. A 20% or greater loss within a wild bird population may adversely impact long-term sustainability (or an EC20). Based on studies for two foraging guilds of birds, the approximate EC20 using blood for piscivores is 2.0 ug/g (wet weight; based on the common loon, Gavia immer) and for invertivores is 1.2 ug/g (wet weight; based on the Carolina wren, Thryothorus Iudovicianus). For mammals, there is greater uncertainty about effects thresholds and lowest observed effect levels (LOELs) are still used because, unlike birds, there are no studies on wild populations describing the impacts on reproductive success. Based on fur Hg concentrations (fresh weight) that relate to biochemical changes in the brain (e.g., ~ 1.0 ug/g, wet weight) a reasonable LOEL for piscivores is 35 ug/g and for invertivores is 10 ug/g. Risk and injury assessments can be used at the individual level, such as through regulatory options with the federal Natural Resource Damage Assessment and Restoration (NRDAR) program, or at the more traditional population level that does not account for the full loss of common resources.
@techreport{
 title = {The effects of methylmercury on wildlife},
 type = {techreport},
 year = {2012},
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 institution = {Penobscot River Mercury Study, Biodiversity Research Institute},
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 abstract = {Published findings indicate that reasonable effects concentrations can be developed for certain taxa, forage guilds, and tissue types that provide replicable and scalable endpoints for assessing risk. The effects of mercury (Hg) on wildlife from 162 studies (n=98 for birds and n=64 for mammals) can generally be grouped under five categories: physiology, neurology, behavior, reproductive, and survival. Studies were differentiated between laboratory, captive, or experimentally manipulated efforts vs. studies of free-living populations. Recent findings demonstrate that (1) available methylmercury (MeHg) can significantly affect the reproductive success for wild populations of birds and mammals, (2) piscivores are at great risk, but invertivores are often times at equal or even at greater risk, especially those taxa associated with prey from wetland habitats, and (3) bird species (and likely mammals) have at least a 11 fold difference in their sensitivity to MeHg toxicity. Changes from the traditional use of point estimates such as lowest observed effect levels to the use of specific effects concentrations (EC) provides a higher resolution approach for assessing risk. The EC level of interest for decision makers should consider the demographics and conservation status of the target species. A 20% or greater loss within a wild bird population may adversely impact long-term sustainability (or an EC20). Based on studies for two foraging guilds of birds, the approximate EC20 using blood for piscivores is 2.0 ug/g (wet weight; based on the common loon, Gavia immer) and for invertivores is 1.2 ug/g (wet weight; based on the Carolina wren, Thryothorus Iudovicianus). For mammals, there is greater uncertainty about effects thresholds and lowest observed effect levels (LOELs) are still used because, unlike birds, there are no studies on wild populations describing the impacts on reproductive success. Based on fur Hg concentrations (fresh weight) that relate to biochemical changes in the brain (e.g., ~ 1.0 ug/g, wet weight) a reasonable LOEL for piscivores is 35 ug/g and for invertivores is 10 ug/g. Risk and injury assessments can be used at the individual level, such as through regulatory options with the federal Natural Resource Damage Assessment and Restoration (NRDAR) program, or at the more traditional population level that does not account for the full loss of common resources.},
 bibtype = {techreport},
 author = {Evers, David}
}
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