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THE EFFECTS OF SHORELINE PROXIMITY ON SPIDER MERCURY CONCENTRATIONS IN WESTERN GREENLAND
Viscioni-Wilson, Lance
Viscioni-Wilson, Lance
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2025-12-18
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Abstract
Mercury (Hg) is emitted through anthropogenic activities such as coal combustion and its deposition into lentic systems through runoff poses a serious ecological threat worldwide. In aquatic ecosystems, inorganic Hg is converted by anaerobic bacteria into the toxic and bioavailable Hg form, methylmercury (MeHg). Methylmercury can then be concentrated by algae and travel to terrestrial ecosystems through emergent aquatic insects that consume those algae. Terrestrial predators like spiders and songbirds subsequently accumulate MeHg by feeding on these insects, increasing the risk of toxic effects in higher trophic level predators through biomagnification. At elevated concentrations, MeHg can be harmful to organisms, acting as a neurotoxin and teratogen and negatively affecting reproductive success. In temperate zones, spiders near shorelines are known to reflect MeHg concentrations of emergent aquatic insects due to a strong reliance on these insects as prey. Little is known about how MeHg varies with distance from Arctic ponds, however. This study investigated the effect of proximity to lentic systems on MeHg concentrations in wolf spiders collected from six ponds on the Pituffik peninsula of western Greenland. Spiders, emergent aquatic insects, and terrestrial insects were collected at three distances (0 m, 10 m, and 35 m) from each of the six ponds. Mercury analyses were conducted on composite samples of spiders and insects. Contrary to patterns documented in temperate ecosystems, spider MeHg concentrations did not differ among collections made at 0 m, 10 m, and 35 m from pond shorelines. Like in temperate zones, emergent aquatic insects exhibited high MeHg, while in contrast to temperate zones, terrestrial insects were also highly contaminated. These concentrations were related to feeding guild, with terrestrial detritivores and predators exhibiting the highest levels of MeHg concentrations, indicating substantial methylation within the detritus-based terrestrial food web. These findings suggest that in the High Arctic, spider contamination is not strongly influenced by distance from water but may instead be driven by a dietary reliance on highly contaminated terrestrial insects. The distinct environmental context of the High Arctic, where permafrost thaw, persistent moisture from snowmelt, and atmospheric deposition may enhance methylation and expand exposure across habitats, helps explain the elevated MeHg observed in multiple prey groups.