EARLY HEARING DETECTION AND INTERVENTION VIRTUAL CONFERENCE
MARCH 2-5, 2021

(Virtually the same conference, without elevators, airplane tickets, or hotel room keys)

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5/24/2021 | 2:00 PM - 3:30 PM | MERCURY ISOTOPIC SIGNATURES ARE TRANSMITTED FROM AQUATIC TO TERRESTRIAL ECOSYSTEMS | Virtual Platform

MERCURY ISOTOPIC SIGNATURES ARE TRANSMITTED FROM AQUATIC TO TERRESTRIAL ECOSYSTEMS

Mercury (Hg) isotopes are increasingly used to identify environmental sources of Hg. Aquatic insects move Hg to terrestrial food webs, but it is unclear if Hg isotopes are conserved during this process. We measured Hg isotopes in spiders, benthic insects, and prey fish in the St. Louis River (SLR, Duluth, MN) and a nearby reference watershed. The lower SLR has industrial Hg sources, whereas the reference watershed receives Hg via atmospheric deposition. Spatial variation in ?202Hg in spiders tracked those of aquatic species. Depleted ?202Hg values confirmed atmospheric source in the reference watershed and the upper SLR. Enriched ?202Hg signatures in the lower SLR confirmed industrial Hg sources to aquatic and riparian food webs. Aquatic insect ?202Hg was strongly correlated with fish ?202Hg (r2 = 0.66) and spider ?202Hg (r2 = 0.75). We found limited evidence of enriched ?202Hg between insects and fish, but not between insects and spiders, suggesting trophic fractionation of Hg isotopes varies across food web pathways. Hg isotope source signatures in aquatic food webs are conserved and transferred into riparian ecosystems, demonstrating the export of legacy Hg in river sediments to floodplain food webs.

Energy flows
Ecotones
Ecological dynamics

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Presenters/Authors

David Walters (), US Geological Survey, waltersd@usgs.gov;