16 From Thin Section to Outcrop: Exploration of Undergraduate Research (Posters)

This session is designed to showcase undergraduate research across all disciplines. All submissions should be written by the student(s) and include a faculty co-author. Categories: Cross-Disciplinary, all topics welcome

Sunday, 22 March 2026
1:30 PM - 5:30 PM
CCC, Ballroom C

Establishing Pre-Dredging Mercury Baselines in Fish Across Legacy-Contaminated and Reference Aquatic Systems

Paper number: 16-26
Program: Technical Sessions
Time: 1:30 PM – 1:30 PM

Authors

Abstract

This study establishes baseline mercury (Hg) concentrations in fish from a pond scheduled for dredging, prior to potential sediment disturbance and contaminant remobilization. Sediment cores from the pond indicate severe legacy Hg contamination, with concentrations reaching over 4500 ppb at 1.6 m depth. In contrast, sediments at the sediment–water interface contain ~200 ppb Hg, consistent with modern (post-1990) atmospheric deposition. Dredging may reintroduce Hg from deeper sediments into the water column, increasing bioavailability to aquatic organisms.

Fish Hg concentrations from this pond were compared with two nearby systems: a protected reservoir with sediment Hg concentrations suggesting no legacy Hg source other than atmospheric (≤190 ppb), and an off-Connecticut River waterbody, where sediment Hg peaks at ~530 ppb at 75 cm depth with values decreasing to ~250 ppb at the sediment-water interface. Fish from all sites were collected by fishing, and muscle and liver tissues were sampled,  freeze-dried, and analyzed for Hg.

Initial results from a variety of species (n = 5) along the Connecticut exhibited a positive relationship (r2 ranging from 0.9 to 0.5) between body size and Hg concentration, consistent with bioaccumulation. In contrast, two stocked trout from the contaminated pond showed relatively low and size-independent Hg concentrations (97 ppb at 37 cm length; 122 ppb at 31 cm), likely reflecting differences in residence time since stocking, dietary differences, or growth dilution. Across sites, liver Hg concentrations were approximately 30% lower than muscle concentrations, consistent with preferential methylmercury binding to cysteine-rich muscle proteins. These results provide a critical pre-dredging benchmark for evaluating future Hg mobilization and ecological risk.

Geological Society of America Abstracts with Programs. Vol. 58, No. 2

doi: 10.1130/abs/2026NE-411331

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