Factors affecting mercury stable isotopic distribution in piscivorous fish of the Laurentian Great Lakes

Environmental Science & Technology
By: , and 
Edited by: Sarah E. JanssenRunsheng YinJacob M. OgorekJohn F. DeWildMichael T. TateThomas M. Holsen, and James P. Hurley

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Abstract

Identifying the sources of methylmercury (MeHg) and tracing the transformations of mercury (Hg) in the aquatic food web are important components of effective strategies for managing current and legacy Hg sources. In our previous work, we measured stable isotopes of Hg (δ202Hg, Δ199Hg, and Δ200Hg) in the Laurentian Great Lakes and estimated source contributions of Hg to bottom sediment. Here, we identify isotopically distinct Hg signatures for Great Lakes trout (Salvelinus namaycush) and walleye (Sander vitreus), driven by both food-web and water-quality characteristics. Fish contain high values for odd-isotope mass independent fractionation (MIF) with averages ranging from 2.50 (western Lake Erie) to 6.18‰ (Lake Superior) in Δ199Hg. The large range in odd-MIF reflects variability in the depth of the euphotic zone, where Hg is most likely incorporated into the food web. Even-isotope MIF (Δ200Hg), a potential tracer for Hg from precipitation, appears both disconnected from lake sedimentary sources and comparable in fish among the five lakes. We suggest that similar to the open ocean, water-column methylation also occurs in the Great Lakes, possibly transforming recently deposited atmospheric Hg deposition. We conclude that the degree of photochemical processing of Hg is controlled by phytoplankton uptake rather than by dissolved organic carbon quantity among lakes.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Factors affecting mercury stable isotopic distribution in piscivorous fish of the Laurentian Great Lakes
Series title Environmental Science & Technology
DOI 10.1021/acs.est.7b06120
Volume 52
Issue 5
Year Published 2018
Language English
Publisher ACS
Contributing office(s) Upper Midwest Water Science Center
Description 9 p.
First page 2768
Last page 2776