Mercury and selenium accumulation in the Colorado River food web, Grand Canyon, USA

Environmental Toxicology and Chemistry
By: , and 

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Abstract

Mercury (Hg) and selenium (Se) biomagnify in aquatic food webs and are toxic to fish and wildlife. The authors measured Hg and Se in organic matter, invertebrates, and fishes in the Colorado River food web at sites spanning 387 river km downstream of Glen Canyon Dam (AZ, USA). Concentrations were relatively high among sites compared with other large rivers (mean wet wt for 6 fishes was 0.17–1.59 μg g–1 Hg and 1.35–2.65 μg g–1 Se), but consistent longitudinal patterns in Hg or Se concentrations relative to the dam were lacking. Mercury increased (slope = 0.147) with δ15N, a metric of trophic position, indicating biomagnification similar to that observed in other freshwater systems. Organisms regularly exceeded exposure risk thresholds for wildlife and humans (6–100% and 56–100% of samples for Hg and Se, respectfully, among risk thresholds). In the Colorado River, Grand Canyon, Hg and Se concentrations pose exposure risks for fish, wildlife, and humans, and the findings of the present study add to a growing body of evidence showing that remote ecosystems are vulnerable to long-range transport and subsequent bioaccumulation of contaminants. Management of exposure risks in Grand Canyon will remain a challenge, as sources and transport mechanisms of Hg and Se extend far beyond park boundaries. Environ Toxicol Chem2015;9999:1–10

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Mercury and selenium accumulation in the Colorado River food web, Grand Canyon, USA
Series title Environmental Toxicology and Chemistry
DOI 10.1002/etc.3077
Volume 34
Issue 10
Year Published 2015
Language English
Publisher Society of Environmental Toxicology and Chemistry
Contributing office(s) Fort Collins Science Center
Description 10 p.
First page 2385
Last page 2394
Country United States
State Arizona
Other Geospatial Colorado River, Grand Canyon
Online Only (Y/N) N
Additional Online Files (Y/N) N