Overview
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Key numbers
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- different isotope systems.15,16 Mercury (Hg) stable isotope
- studied. Apart from smaller scale field studies,17,24 Hg stable
- terrestrial habitats, is the use of paired, light stable isotope Accepted: August 21, 2023
- feeding ecologies. Mercury stable isotopes are increasingly tion.29,30 HgT was analyzed via direct combustion coupled
- Samples were prepared via hot nitric acid digestion with 10%
- intensive sampling effort to assess the connection between Almaden) (Table S1). Hg isotope data for sediment and
- River, we found that δ202Hg ranged from −1.16‰ to 0.29‰ River and Bad River, and the results revealed a complex mixing
- and Δ199Hg ranged from −0.06‰ to 0.39‰ (Figure S2), of Hg from legacy contamination, terrestrially derived
- exceeding the previous δ202Hg range measured in spider tissues watershed runoff, and precipitation.27 Previous isotope assess-
- habitats, it was unclear if the range in δ202Hg and Δ199Hg truly sediment source gradient, denoted by fraction industrial
- Dragonflies had a range (−1.11‰ to −0.07‰) similar to that These findings demonstrate that Hg isotopes in tetragnathids
- the %MeHg (Figure S3), indicating that varying %MeHg
- Δ199Hg were on average 0.17 ± 0.11‰ (n = 41), with the Figure 2. Relative differences in δ202Hg in tetragnathids compared to
- value (Table S2), indicating little overall change to δ202Hg. tetragnathids than in araneids (mean difference of −0.18 ±
- Hence, we conclude that the range of δ202Hg observed in 0.11‰ in δ202Hg), whereas more variability was observed
- tetragnathids in this study is attributed to differences in dietary between pisaurid and tetragnathid δ202Hg values (Table S3).
- δ202Hg range corresponds to a gradient of Hg sources tetragnathids and pisaurids to differences in hunting strategies
- building by tetragnathids that target emergent flying insects.9 foraging ranges45 and internal detoxification processes.19,20
- differences in %MeHg between araneids (70 ± 9%) and energy transfer mechanisms in shoreline environments. In
- tetragnathids (81 ± 12%) (Table S3). Comparison of Δ199Hg summary, shoreline spiders have the potential to be utilized as
- (mean difference of −0.16 ± 0.04‰ (standard error) Δ199Hg), mercury (e.g., industrial, precipitation, and terrestrially derived
- (mean difference of −0.02 ± 0.03‰ (standard error) Δ199Hg) monitoring efforts for Hg-sensitive regions.
- S1); and summary tables of Hg stable isotope data in
- Hg stable isotope ratios for contaminated site remediation25 97331, United States; orcid.org/0000-0003-1329-5285
- (USGS) Environmental Health Program as well as the U.S. (16) Tsui, M. T.-K.; Blum, J. D.; Kwon, S. Y. Review of stable
- (5) Kraus, J. M. Contaminants in linked aquatic−terrestrial A Review of Insights from Mercury Stable Isotopes. Environ. Sci.
- (6) Chumchal, M. M.; Drenner, R. W. An environmental problem Factors Affecting Mercury Stable Isotopic Distribution in Piscivorous
- Toxicol. Chem. 2022, 41 (3), 499−514. Choi, J. W. Mercury stable isotopes for monitoring the effectiveness of
- (30) U.S. Environmental Protection Agency (EPA). Method 1630: songbirds with stable mercury isotopes: Challenges and future
- Nitrogen) Stable Isotopes. U.S. Geological Survey data release. 2021.
Methods (brief)
- effectiveness. To examine aquatic to terrestrial Hg transfer, we collected shoreline
- collection sites.27 Previously reported yellow perch data27 were not available at all 14 habitat locations where spiders and dragonflies were collected.
- Error bars represent one standard deviation (SD) of samples collected from a site (e.g., site variability), and symbols without error bars represent a
- single composite sample collected at a site. The dashed lines are regression slopes. The error for δ202Hg is represented as two SDs of the certified
- In this study, we use Hg stable isotope ratios to assess if spp.) were collected from emergent and riparian vegetation
- shoreline spiders reflect a gradient of aquatic Hg sources (e.g., using previously established methods.28 We also sampled two
- being utilized for site assessments25 and evaluation of global to atomic absorption spectroscopy31 or, in the case of limited
- scale Hg mitigation efforts;26 therefore, it is imperative to mass samples, via bromination of the MeHg extract27 followed
- Site Information and Sample Collection. Biological
- Samples were prepared via hot nitric acid digestion with 10%
- samples (spiders, dragonfly larvae, and yellow perch (Perca ductively coupled mass spectrometer following previously
- f lavescens)) and sediments were collected within the St. Louis established protocols.33 Quality control and assurance during
- lower estuary of the St. Louis River were collected as part of an 407) and secondary check standards (NIST RM 8610, UM
- were sampled, encompassing 41 sampling sites and four Emergent Insects. The examination of Hg isotope values in
- collected across all habitats had variable MeHg contents (78
- tion.23 We expect positive Δ199Hg in these samples to be
- and game fish collected from the lower St. Louis River observations across sites for tetragnathid vs pisaurid (green) and
- when collecting samples may result in inaccurate interpreta-
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