Spatial patterns of mercury contamination and associated risk to piscivorous wading birds of the south central United States

Abstract

Piscivorous birds are top predators in aquatic ecosystems and are vulnerable to mercury (Hg) exposure and associated adverse health effects. In some areas of North America, the health risk posed to piscivorous birds by Hg contamination has not been characterized because concentrations of Hg in bird tissues have not been extensively monitored. When data on Hg in tissues of piscivorous birds are not available, the concentration of Hg in the blood of piscivorous birds can be estimated from the concentration of Hg in prey fish. We used concentrations of Hg in different lengths of a proxy prey fish, bluegill (Lepomis macrochirus), to estimate the concentration of Hg in the blood of 4 species of adult piscivorous wading birds (little blue herons [Egretta caerulea], green herons [Butorides virescens], great egrets [Ardea albus], and great blue herons [Ardea herodias]) in 14 ecoregions of the south central United States. The 4 species of birds consume different sizes of fish with different concentrations of Hg and were predicted to have different concentrations of Hg in their blood, with little blue herons < green herons < great egrets < great blue herons. For each species of bird, there were significant differences in average estimated concentrations of Hg in blood between ecoregions, with estimated concentrations of Hg in blood increasing with Hg deposition. The level of predicted risk varied with ecoregion and bird species and was highest for great blue herons. We recommend that future studies of Hg contamination of piscivorous wading birds of the southern United States focus on great blue herons in water bodies within ecoregions that have high Hg deposition. Environ Toxicol Chem 2019;38:160–166. © 2018 SETAC

Relationship Between Methylmercury Contamination and Proportion of Aquatic and Terrestrial Prey in Diets of Shoreline Spiders

“…In aquatic systems, inorganic mercury can be converted to highly toxic and accumulative methylmercury (MeHg) that enters the food chain and results in aquatic organisms being contaminated with MeHg (Chen and Driscoll 2018). Organisms feeding near the top of aquatic food webs, like piscivorous fish and birds, can accumulate concentrations of MeHg high enough to pose a threat to their health (Scheuhammer et al 2007;Wiener 2013;Gerstle et al 2019).…”

Effect of Land Cover on Ecoregion‐Scale Spatial Patterns of Mercury Contamination of Largemouth Bass in the Southeastern United States

“…These regions are critical for structuring and implementing ecosystem management strategies across federal agencies, state agencies, and nongovernmental organizations that are responsible for different types of resources within the same geographic areas (McMahon et al, 2001; Omernik & Griffith, 2014). Our previous investigations demonstrated that average concentrations of MeHg in centrarchids were significantly different between 14 Level III ecoregions located in six states: Texas, Oklahoma, Arkansas, Louisiana, Mississippi, and Tennessee (Drenner et al, 2011; Gerstle et al, 2019).…”

“…Our study focused on the southeastern United States, defined as a 15-state area from Texas to Maryland that accounts for 33% of the land area of the continental United States (https://www.census.gov/geographies/reference-files/ 2010/geo/state-area.html; Figure 1A). Although there have been studies of Hg contamination in fish within subregions of the southeastern United States (Adams et al, 2016;Drenner et al, 2011Drenner et al, , 2013Dong et al, 2016;Gerstle et al, 2019;Glover et al, 2010;Lange et al, 1993;Sackett et al, 2009Sackett et al, , 2013Sherman & Blum, 2013;Sveinsdottir & Mason, 2005), there has not been a comprehensive analysis of spatial patterns of Hg contamination of fish across the entire southeastern United States as have been conducted in the western United States and Canada (e.g., Eagles-Smith et al, 2016a;Lepak et al, 2016), the Laurentian Great Lakes Area (e.g., Monson et al, 2011;Sandheinrich et al, 2011), and the northeastern United States (e.g, Kamman et al, 2005;Shanley et al, 2012).…”

“…We used the National Descriptive Model of Mercury in Fish (NDMMF; Wente, 2004) to predict Hg concentrations in skin-off fillets of largemouth bass-equivalents (hereafter largemouth bass). Because it is impractical to collect fish of the same size and species from different water bodies over large regions (Wente, 2004), the NDMMF has been widely used to estimate Hg concentrations in a common size and species of fish from water bodies that have been previously sampled (Adams et al, 2016;Depew et al, 2013b;Drenner et al, 2011Drenner et al, , 2013Gerstle et al, 2019).…”

Evidence of Low-Habitat Contamination Using Feathers of Three Heron Species as a Biomonitor of Inorganic Elemental Pollution

“…For instance, exposure to cadmium (Cd), mercury (Hg), and selenium (Se) negatively affects the body mass/condition and health of birds by reducing their growth or body weight and, consequently, it harms survival and reproductive success [ 14 , 15 ]. Hg accumulated in body tissues can adversely affect reproduction, especially in higher trophic level species, such as fish-eating birds [ 16 , 17 , 18 ].…”