Mercury risk to avian piscivores across western United States and Canada - PubMed (original) (raw)

Mercury risk to avian piscivores across western United States and Canada

Allyson Jackson et al. Sci Total Environ. 2016.

Abstract

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 limits 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=36cm, Osprey=30cm, Common and Yellow-billed Loon=15cm, Western and Clark's Grebe=6cm, and Belted Kingfisher=5cm) 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 (<0.5μg/g), low (0.5-1μg/g), moderate (1-2μg/g), high (2-3μg/g), and extra high (>3μg/g). These risk categories were used to estimate potential mercury risk to avian piscivores across the west at a 1degree-by-1degree grid cell resolution. Avian piscivores foraging on larger-sized fish generally were at a higher relative risk to Hg. Habitats with a 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.

Keywords: Bioindicator; Fish; Methylmercury; Risk assessment.

Copyright © 2016 Elsevier B.V. All rights reserved.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Whole blood Hg (μg/g wet weight) comparison across 20 avian piscivores in western United States and Canada. Birds (including sample size) are shown in taxonomic order. Egg and liver samples were converted into whole blood equivalent to aid in comparison using Equation 1 and 2 (see text).

Figure 2

Figure 2

Distribution of avian samples (blood, egg, and liver combined) for target piscivores across their breeding ranges in western United States and Canada. The study area in western United States and Canada is shown in gray. Each species breeding range is show in green. Loons include Common Loons and Yellow-billed Loons (c). Grebes include Western Grebes and Clark’s Grebes (d). There were no bird data for Belted Kingfishers (e).

Figure 3

Figure 3

Relative Hg risk per 1 degree grid cell across the North American breeding range of five target freshwater piscivore species: a) Bald Eagle, b) Osprey, c) Loons (Common and Yellow-billed), d) Grebes (Clark’s and Western), and e) Belted Kingfisher. The prey fish were size-corrected according to the preference of each species: Bald Eagle = 36 cm, Osprey = 30 cm, Loons = 15 cm, Grebes = 6 cm, Belted Kingfisher = 5 cm. All Hg concentrations have been converted to wet weight whole bird blood for comparison. Low confidence is estimated as any grid cell where the standard error is more than one quarter of the mean.

Figure 4

Figure 4

Areas of western United States and Canada where fish modeling indicates high confidence in moderate or higher relative Hg risk. Light colors indicate fewer species with overlapping risk. Empty grid cells indicate areas where fish data was modeled but risk was estimated to be low. Areas not covered by grid cells either have least square mean estimates with low confidence or no fish data to use in the model.

Similar articles

Cited by

References

    1. Ackerman JT, Eagles-Smith CA, Takekawa JY, Demers SA, Adelsbach TL, Bluso JD, Miles AK, Warnock N, Suchanek TH, Schwarzbach SE. Mercury concentrations and space use of pre-breeding American avocets and black-necked stilts in San Francisco Bay. Sci Total Environ. 2007;384:452–466. - PubMed
    1. Ackerman JT, Eagles-Smith CA, Takekawa JY, Bluso JD, Adelsbach TL. Mercury concentrations in blood and feathers of pre-breeding Forster’s terns in relation to space use of San Francisco Bay habitats. Environ Tox Chem. 2008;27:897–908. - PubMed
    1. Ackerman JT, Hartman CA, Eagles-Smith CA, Herzog MP, Davis JA, Ichikawa G, Bonnema A. Estimating mercury exposure of piscivorous birds and sport fish using prey fish monitoring. Environ Sci Technol. 2015;49:13596–13604. - PubMed
    1. Ackerman JT, Eagles-Smith CA, Herzog MP, Hartman CA. Maternal transfer of contaminants in birds: mercury and selenium concentrations in parents and their eggs. Environ Poll. 2016;210:145–154. - PubMed
    1. Ackerman JT, Eagles-Smith CA, Herzog MP, Hartman CA, Peterson SH, Evers DC, Jackson AK, Elliott JE, Vander Pol SS, Bryan CE. Avian mercury exposure and risk across western North America: a synthesis. Sci Total Environ this issue. - PMC - PubMed

MeSH terms

Substances

LinkOut - more resources