Thesis
Effects of chironomid density and dissolved oxygen on mercury efflux from profundal lake sediment from Deer Lake, Washington
Washington State University
Master of Science (MS), Washington State University
2011
Handle:
https://hdl.handle.net/2376/104699
Abstract
Macrobenthos in aquatic sediments can greatly affect the exchange of chemical compounds at the sediment-water interface due to bioturbation and bioirrigation. This study explored the effects of chironomid density and dissolved oxygen on methylmercury efflux from profundal sediments from a freshwater lake. A series of sediment-water interface chamber incubations were conducted on sediment collected from Deer Lake, WA (Zmax = 22.9 m, A = 445 ha), an oligo-mesotrophic lake near Spokane, WA. Experimental chambers were incubated under low and high densities of chironomid larvae native to the lake sediments. The first and second incubations varied in dissolved oxygen concentration in chamber water, which was then monitored for total mercury and methylmercury, the toxic form of mercury that accumulates in the aquatic food web. Our hypothesis was that an increase in chironomid density would cause an increase in methylmercury efflux from the sediment, and a second hypothesis that a decrease in dissolved oxygen would also cause an increase in methylmercury efflux. For the high DO incubation (~5.0 mg/L), the flux rate for dissolved methylmercury was 0.03 ± 0.16 ng/m2 /d for ambient density chambers and 0.18 ± 0.05 ng/m2 /d for high density chambers (n=4), with a significant difference in dissolved methylmercury efflux. Similar results were found for the low DO incubation (~2.5 mg/L), with a rate of dissolved methylmercury as 0.16 ± 0.06 ng/m2 /d for ambient density chambers and 0.38 ± 0.07 ng/m2 /d for high density chambers, with a significant difference in dissolved methylmercury efflux. An analysis of variance (ANOVA) was performed comparing the two incubations that showed dissolved oxygen was a significant factor. Overall, both hypotheses were supported. Additionally, total methylmercury, total mercury and nutrients were analyzed to support these hypotheses. This study provides a better understanding of the effects of macrobenthos and dissolved oxygen on mercury cycling at the sediment-water interface of freshwater lakes that will inform the development of lake management strategies to better manage aquatic biota uptake of mercury.
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Details
- Title
- Effects of chironomid density and dissolved oxygen on mercury efflux from profundal lake sediment from Deer Lake, Washington
- Creators
- Suzanne Elaine Cox
- Contributors
- Marc W. Beutel (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525375201842
- Language
- English
- Resource Type
- Thesis