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Historic Patterns of Deposition and Biomagnification of Mercury in Selected Wetland Systems

Brenda, Leady Sue Simmers
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372863246

Abstract Details

2013, Doctor of Philosophy, University of Toledo, Biology (Ecology).
Mercury (Hg) is a global pollutant impacting wildlife and humans, even at low levels. I addressed four topics in environmental Hg research that have not been emphasized in the literature. First, I examined the utility of lake sediment cores in documenting Hg input and output from a system. I tested the similarity of records of US industrial Hg consumption (&#x201c;environmental input&#x201d;) and tissue levels in walleye (Stizostedion vitreum vitreum) (&#x201c;biological output&#x201d;) with Hg stratigraphy in cores from the western basin of Lake Erie. Hg consumption correlated with Hg accumulation rates in one core (R2=0.39, p<0.001) but not in the other. Hg accumulation rates correlated with the history of walleye tissue Hg levels in both cores (p<0.001). The model for fish tissue levels calculated a 1945 mean of 80 ng Hg g-1 (similar to reported results of 75 ng Hg g-1) and hind-casted a mean of 17 ng Hg g-1for ca. 1900 fish tissue levels, providing a reasonable restoration target. Second, I compared mercury dynamics in two regions of a tropical wetland differing in their history of mercury contamination. I found a significant impact of Hg in the northern Pantanal (Brazil), an area with a recent history of gold mining, as compared to a 200km distant reference site in the same wetland. Average pre-1940 Hg accumulation in cores was not significantly different (N=5, p=0.14) between both regions and comparable with rates calculated for global reference sites. Post gold-rush Hg (post-1980) deposition was more than 1.5 times higher than the post-1980 rate in the reference sites, implying a regional Hg effect of gold mining. A significant impact on sediments, plants, and fish was also found. Salvinia auriculata, suggested as a biological monitor for Hg pollution, contained almost four times more Hg in the northern Pantanal (90.7 &#xb1; 9.1 ng gdry-1) than in the reference site (24.5 &#xb1; 3.3 ng gdry-1). Third, I contrasted Hg biomagnification in a temperate and tropical system. A significant directional increase in both methyl Hg (MeHg) and total Hg (THg) was found in both the Lake Erie East Marsh (both p=0.001) and Pantanal trophic levels (THg p=0.0002, MeHg p=0.001). Biomagnification factors, the magnitude of change in mercury burden between trophic levels, were similar in the top predator in each system (East Marsh, Micropterus 5.5; Pantanal, Pygocentrus 6.2) but the magnitude from omnivores to top predator was different (East Marsh 53.6 versus Pantanal 9.6). The rate of increase in Hg tissue levels as fish increase in size was highest in the top predator in each system and decreased with decreasing trophic level. Finally, I examined the role of selective predation on Hg dynamics through a literature synthesis. Hg impaired predators may favor easy to capture prey that, in turn, are Hg impaired. This exacerbates biomagnification and suggests a new aspect of optimal foraging theory. I outlined lab and field studies to examine this impact in predatory fish. Mechanisms involved in Hg magnification along food chains deserve more attention, particularly in tropical regions where the threat of chronic exposure to this neurotoxin may have the greatest implications for biodiversity.
Johan Gottgens, Ph.D. (Committee Chair)
Elliot Tramer , Ph.D. (Committee Member)
Frederick Williams, Ph.D. (Committee Member)
Allison Spongberg, Ph.D. (Committee Member)
Timothy Fisher, Ph.D. (Committee Member)
159 p.
Environmental Science
mercury biomagnification Lake Erie Pantanal Brazil

Recommended Citations

Citations

  • Brenda, L. S. S. (2013). Historic Patterns of Deposition and Biomagnification of Mercury in Selected Wetland Systems [Doctoral dissertation, University of Toledo]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372863246

    APA Style (7th edition)

  • Brenda, Leady. Historic Patterns of Deposition and Biomagnification of Mercury in Selected Wetland Systems. 2013. University of Toledo, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372863246.

    MLA Style (8th edition)

  • Brenda, Leady. "Historic Patterns of Deposition and Biomagnification of Mercury in Selected Wetland Systems." Doctoral dissertation, University of Toledo, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1372863246

    Chicago Manual of Style (17th edition)

toledo1372863246
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© 2013, all rights reserved.
This open access ETD is published by University of Toledo and OhioLINK.