The Impact of Mercury Exposure on the Common Loon (<i>Gavia immer</i>) Population in the Adirondack Park, New York, USA

Schoch, Nina; Glennon, Michale J.; Evers, David C.; Duron, Melissa; Jackson, Allyson K.; Driscoll, Charles T.; Ozard, J.; Sauer, Amy K.

doi:10.1675/063.037.sp116

Cited by 18 publications

(7 citation statements)

References 25 publications

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“…The LOAEL identified by Evers et al for loons in Maine and New Hampshire (0.16 mg/kg in prey) does not account for the characteristic intercorrelation of Hg exposures and prey availability (both a function of lake pH). A recent study of loon reproduction in the Adirondack Mountains (NY, USA) shares the same limitation.…”

Section: Literature Review Resultsmentioning

confidence: 98%

Toxicity reference values for methylmercury effects on avian reproduction: Critical review and analysis

Fuchsman

Brown

Henning

et al. 2016

Enviro Toxic and Chemistry

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Effects of mercury (Hg) on birds have been studied extensively and with increasing frequency in recent years. The authors conducted a comprehensive review of methylmercury (MeHg) effects on bird reproduction, evaluating laboratory and field studies in which observed effects could be attributed primarily to Hg. The review focuses on exposures via diet and maternal transfer in which observed effects (or lack thereof) were reported relative to Hg concentrations in diet, eggs, or adult blood. Applicable data were identified for 23 species. From this data set, the authors identified ranges of toxicity reference values suitable for risk-assessment applications. Typical ranges of Hg effect thresholds are approximately 0.2 mg/kg to >1.4 mg/kg in diet, 0.05 mg/kg/d to 0.5 mg/kg/d on a dose basis, 0.6 mg/kg to 2.7 mg/kg in eggs, and 2.1 mg/kg to >6.7 mg/kg in parental blood (all concentrations on a wet wt basis). For Hg in avian blood, the review represents the first broad compilation of relevant toxicity data. For dietary exposures, the current data support TRVs that are greater than older, commonly used TRVs. The older diet-based TRVs incorporate conservative assumptions and uncertainty factors that are no longer justified, although they generally were appropriate when originally derived, because of past data limitations. The egg-based TRVs identified from the review are more similar to other previously derived TRVs but have been updated to incorporate new information from recent studies. While important research needs remain, a key recommendation is that species not yet tested for MeHg toxicity should be evaluated using toxicity data from tested species with similar body weights. Environ Toxicol Chem 2017;36:294-319. # 2016 SETAC

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Section: Literature Review Resultsmentioning

confidence: 98%

Toxicity reference values for methylmercury effects on avian reproduction: Critical review and analysis

Fuchsman

Brown

Henning

et al. 2016

Enviro Toxic and Chemistry

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“…Published literature has demonstrated field-based Hg exposure and related effects in many species of avian piscivores (Ackerman et al, this issue . ; Burgess and Meyer 2008; Evers et al, 2008a; Depew et al, 2012; Schoch et al, 2014), and avian piscivores are key bioindicators for many long-term monitoring programs (Braune 2007; Evers et al, 1998; Monteiro and Furness, 1995) and site-specific assessments (Guigueno et al, 2012; Weech et al, 2006). As part of a cross-national assessment of Hg cycling, distribution, and bioaccumulation (Western North America Mercury Synthesis), Hg risk to avian piscivores was assessed for Western North America – a region spanning north to Alaska, south to Arizona, west to the Pacific, and east to the Dakotas (see overview in Eagles-Smith et al, this issue [a] ).…”

Section: 0 Introductionmentioning

confidence: 99%

Mercury risk to avian piscivores across western United States and Canada

Jackson

Evers

Eagles‐Smith

et al. 2016

Science of The Total Environment

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The widespread distribution of mercury (Hg) threatens wildlife health, particularly piscivorous birds. Western North America is a diverse region that provides critical habitat to many piscivorous bird species, and also has a well-documented history of mercury contamination from legacy mining and atmospheric deposition. The diversity of landscapes in the west limit the distribution of avian piscivore species, complicating broad comparisons across the region. Mercury risk to avian piscivores was evaluated across the Western United States and Canada using a suite of avian piscivore species representing a variety of foraging strategies that together occur broadly across the region. Prey fish Hg concentrations were size-adjusted to the preferred size class of the diet for each avian piscivore (Bald Eagle=36 cm, Osprey=30 cm, Common and Yellow-billed Loon=15 cm, Western and Clark’s Grebe=6 cm, and Belted Kingfisher=5 cm) across each species breeding range. Using a combination of field and lab-based studies on Hg effect in a variety of species, wet weight blood estimates were grouped into five relative risk categories including: background (<0.5 μg/g), low (0.5 – 1 μg/g), moderate (1 – 2 μg/g), high (2 – 3 μg/g), and extra high (>3 μg/g). These risk categories were used to estimate potential mercury risk to avian piscivores across the west at a 1 degree-by-1 degree grid cell resolution. Avian piscivores foraging on larger-sized fish generally were at higher relative risk to Hg. Habitats with relatively high risk included wetland complexes (e.g., prairie pothole in Saskatchewan), river deltas (e.g., San Francisco Bay, Puget Sound, Columbia River), and arid lands (Great Basin and central Arizona). These results indicate that more intensive avian piscivore sampling is needed across western North America to generate a more robust assessment of exposure risk.

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“…, Schoch et al. ), leaving a gap in understanding about MeHg bioaccumulation by terrestrial non‐piscivorous predators. Furthermore, studies have reported high MeHg concentrations in endangered insectivorous wildlife such as little brown bats (Wada et al.…”

Section: Introductionmentioning

confidence: 99%

Dissolved organic carbon modulates mercury concentrations in insect subsidies from streams to terrestrial consumers

Chaves-Ulloa

Taylor

Broadley

et al. 2016

Ecological Applications

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Mercury (Hg) concentrations in aquatic environments have increased globally, exposing consumers of aquatic organisms to high Hg levels. For both aquatic and terrestrial consumers, exposure to Hg depends on their food sources as well as environmental factors influencing Hg bioavailability. The majority of the research on the transfer of methylmercury (MeHg), a toxic and bioaccumulating form of Hg, between aquatic and terrestrial food webs has focused on terrestrial piscivores. However, a gap exists in our understanding of the factors regulating MeHg bioaccumulation by non-piscivorous terrestrial predators, specifically consumers of adult aquatic insects. Because dissolved organic carbon (DOC) binds tightly to MeHg, affecting its transport and availability in aquatic food webs, we hypothesized that DOC affects MeHg transfer from stream food webs to terrestrial predators feeding on emerging adult insects. We tested this hypothesis by collecting data over two years from 10 low-order streams spanning a broad DOC gradient in the Lake Sunapee watershed in New Hampshire. We found that streamwater MeHg concentration increased linearly with DOC concentration. However, streams with the highest DOC concentrations had emerging stream prey and spiders with lower MeHg concentrations than streams with intermediate DOC concentrations; a pattern that is similar to fish and larval aquatic insects. Furthermore, high MeHg concentrations found in spiders show that MeHg transfer in adult aquatic insects is an overlooked but potentially significant pathway of MeHg bioaccumulation in terrestrial food webs. Our results suggest that although MeHg in water increases with DOC, MeHg concentrations in stream and terrestrial consumers did not consistently increase with increases in streamwater MeHg concentrations. In fact, there was a change from a positive to a negative relationship between aqueous exposure and bioaccumulation at streamwater MeHg concentrations associated with DOC above around 5 mg/L. Thus, our study highlights the importance of stream DOC for MeHg dynamics beyond stream boundaries, and shows that factors modulating MeHg bioavailability in aquatic systems can affect the transfer of MeHg to terrestrial predators via aquatic subsidies.

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The Impact of Mercury Exposure on the Common Loon (Gavia immer) Population in the Adirondack Park, New York, USA

Cited by 18 publications

References 25 publications

Toxicity reference values for methylmercury effects on avian reproduction: Critical review and analysis

Toxicity reference values for methylmercury effects on avian reproduction: Critical review and analysis

Mercury risk to avian piscivores across western United States and Canada

Dissolved organic carbon modulates mercury concentrations in insect subsidies from streams to terrestrial consumers

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