Hg‐contaminated terrestrial spiders pose a potential risk to songbirds at Caddo Lake (Texas/Louisiana, USA)

Gann, Gretchen Lee; Powell, Cleveland H.; Chumchal, Matthew M.; Drenner, Ray W.

doi:10.1002/etc.2796

Cited by 39 publications

(58 citation statements)

References 24 publications

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“…near Caddo Lake (Texas/Louisiana, USA) and its associated wetlands exceeded the minimum tissue MeHg concentrations (19.4–256 ng/g) that would cause physiological impairment in arachnivorous birds (USEPA ), and the mean MeHg concentration found in Tetragnatha spiders in this study was 3.9 times higher than the highest MeHg concentration reported by Gann et al. (). Moreover, MeHg concentrations in spiders in our study sites were also higher than in fish collected from the same streams (H. J. Broadley et al., unpublished manuscript ), emphasizing the importance of MeHg bioaccumulation across aquatic–terrestrial boundaries in non‐piscivorous terrestrial consumers.…”

Section: Discussioncontrasting

confidence: 57%

“…Gann et al. () found that Tetragnatha sp. near Caddo Lake (Texas/Louisiana, USA) and its associated wetlands exceeded the minimum tissue MeHg concentrations (19.4–256 ng/g) that would cause physiological impairment in arachnivorous birds (USEPA ), and the mean MeHg concentration found in Tetragnatha spiders in this study was 3.9 times higher than the highest MeHg concentration reported by Gann et al.…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Discussioncontrasting

confidence: 57%

Section: Discussionmentioning

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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“…Odonate‐based avian wildlife values were calculated to assess the exposure risk for nestling red‐winged blackbirds at the study site using methods modified from the US Environmental Protection Agency , Lazorchak et al , Walters et al , and Gann et al (Supplemental Data). Odonate‐based avian wildlife values reflect the minimum MeHg concentrations in odonates, consumed by birds in normal proportions of the total diet, required to create physiologically significant doses .…”

Section: Methodsmentioning

confidence: 99%

Seasonality of odonate‐mediated methylmercury flux from permanent and semipermanent ponds and potential risk to red‐winged blackbirds (Agelaius phoeniceus)

Williams

Chumchal

Drenner

et al. 2017

Enviro Toxic and Chemistry

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Methylmercury (MeHg) is an aquatic contaminant that can be transferred to terrestrial predators by emergent aquatic insects such as odonates (damselflies and dragonflies). We assessed the effects of month and pond permanence on odonate-mediated MeHg flux (calculated as emergent odonate biomass × MeHg concentration) in 10 experimental ponds and the potential risk to nestling red-winged blackbirds (Agelaius phoeniceus) posed by consuming MeHg-contaminated odonates. Emergent odonates were collected weekly from permanent ponds with bluegill (Lepomis macrochirus; n = 5) and semipermanent ponds without fish (n = 5) over an 8-mo period (January-August 2015). The MeHg flux from damselflies, aeshnid dragonflies, and libellulid dragonflies began in March and peaked in April, May, and June, respectively, and then declined throughout the rest of the summer. Odonate-mediated MeHg flux from semipermanent ponds without fish was greater than that from permanent ponds with fish. Nesting of red-winged blackbirds overlapped with peak odonate emergence and odonate-mediated MeHg flux. Because their diet can be dominated by damselflies and dragonflies, we tested the hypothesis that MeHg-contaminated odonates may pose a health risk to nestling red-winged blackbirds. Concentrations of MeHg in odonates exceeded wildlife values (the minimum odonate MeHg concentrations causing physiologically significant doses in consumers) for nestlings, suggesting that MeHg-contaminated odonates can pose a health risk to nestling red-winged blackbirds. Environ Toxicol Chem 2017;36:2833-2837. © 2017 SETAC.

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“…Shoreline spiders have been proposed as biosentinels that could be used to monitor biomagnifying contaminants in aquatic ecosystems (Walters et al 2008(Walters et al , 2009Otter et al 2013;Tweedy et al 2013) and provide insight into the risk posed by contaminants to birds that feed on spiders (Walters et al 2009;Gann et al 2015). Most studies have focused on long-jawed orb weavers that have potential as biosentinels because they have a wide geographic distribution, occur at high densities, and specialize in the consumption of emergent aquatic insects (Walters et al 2008).…”

Section: Resultsmentioning

confidence: 99%

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

Ortega‐Rodriguez

Chumchal

Drenner

et al. 2019

Enviro Toxic and Chemistry

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Terrestrial organisms such as shoreline spiders that consume prey from aquatic food webs can be contaminated with methylmercury (MeHg). However, no studies have examined the relationship between MeHg contamination of shoreline spider taxa and the proportion of aquatic and terrestrial prey in their diets. The present study had 2 objectives: 1) determine concentrations of MeHg in 7 taxa of shoreline spiders, and 2) assess the relationship between concentrations of MeHg in spiders and the proportion of aquatic and terrestrial prey in spider diets. We collected shoreline spiders, emergent aquatic insects, and terrestrial insects from in and around 10 experimental ponds. Methylmercury concentrations were greatest in spiders, intermediate in aquatic insects, and lowest in terrestrial insects. The elevated MeHg concentrations in spiders indicate that they were feeding, at least in part, on emergent aquatic insects. However, variability in MeHg concentration observed among spider taxa suggested that the proportion of aquatic and terrestrial prey in spider diets likely varied among taxa. We estimated the proportion of aquatic and terrestrial prey in the diet of each spider taxon from the nitrogen (δ15N) and carbon (δ13C) isotope values of spiders and their potential aquatic and terrestrial prey items. The median proportion of aquatic prey in spider diets varied by almost 2‐fold, and MeHg concentrations in shoreline spiders were strongly correlated with the proportion of aquatic prey in their diet. In the present study, we demonstrate for the first time that the degree of connectivity to aquatic food webs determines MeHg contamination of shoreline spiders. Environ Toxicol Chem 2019;38:2503–2508. © 2019 SETAC

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Hg‐contaminated terrestrial spiders pose a potential risk to songbirds at Caddo Lake (Texas/Louisiana, USA)

Cited by 39 publications

References 24 publications

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

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

Seasonality of odonate‐mediated methylmercury flux from permanent and semipermanent ponds and potential risk to red‐winged blackbirds (Agelaius phoeniceus)

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

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