Thesis
Effects of hypolimnetic oxygenation on carbon and nitrogen stable isotope compositions of Lake Zoobenthos in eastern Washington
Washington State University
Master of Science (MS), Washington State University
2013
Handle:
https://hdl.handle.net/2376/101531
Abstract
As organic lake sediments are biodegraded, microorganisms deplete surrounding dissolved oxygen (DO) supplies. Anaerobic organic lake sediments are ideal media for methanogenic Archaea. Freshwater biogenic methane (CH4) is 13C-depleted in comparison to the organic sediments it is derived from. Methane-oxidizing bacteria (MOB) further discriminate against 13C in the oxidation process. Due to the unique !13C signature of biogenic CH4, stable isotope analysis (SIA) is a powerful tool for estimating contribution of CH4-derived energy within lake freshwater food webs. Previous SIA studies have found significant levels of CH4-derived biomass in benthic invertebrates (i.e. Chironomidae, Oligochaeta) and zooplankton in eutrophic lakes. Additionally, hypolimnetic DO concentrations have been found to play a critical role in these invertebrates’ stable isotope compositions. In eutrophic lakes, hypolimnetic oxygenation (HO) is used to restore DO levels at the sediment-water interface (SWI) to prevent internal phosphorous recycling, decrease reduced metal flux, and increase fish habitat. Because DO concentrations at the SWI have strong influences on CH4 flux and oxidation, HO may have significant effects on zoobenthos stable isotope compositions. Little work has been conducted on the effects of HO on the stable isotope compositions of profundal invertebrates, and whether HO effects MOB utilization within lakes. vi Our objective was to determine if HO decreases zoobenthos consumption of MOB, by limiting CH4 available to be oxidized at autumn turnover. To test whether HO had any influence on zoobenthos utilization of MOB, we compared chironomid (Diptera: Chironomidae), oligochaete (Annelida: Oligochaeta), and Chaoborus sp. (Diptera: Chaoboridae) stable isotope values collected from three eastern Washington lakes: Newman Lake (20 years HO); North Twin Lake (5 years HO); and South Twin Lake (unoxygenated). Chironomidae larvae showed the most dietary MOB influence. Oligochaete worms and Chaoborus larvae showed little MOB influence. Chaoborus migrating through the oxic-anoxic interface showed little evidence of MOB utilization. Lakes with HO had higher amounts of dietary MOB influence in chironomid larvae. MOB activity may be increased at the SWI, and decreased in the water column in lakes with HO.
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Details
- Title
- Effects of hypolimnetic oxygenation on carbon and nitrogen stable isotope compositions of Lake Zoobenthos in eastern Washington
- Creators
- Andrew Wright Child
- Contributors
- Barry C. Moore (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525394101842
- Language
- English
- Resource Type
- Thesis