Date of Award

Spring 5-2015

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Chair

Kevin A. Kuehn

Committee Chair Department

Biological Sciences

Committee Member 2

Micheal A. Davis

Committee Member 2 Department

Biological Sciences

Committee Member 3

Carl Qualls

Committee Member 3 Department

Biological Sciences

Abstract

Field studies were conducted to examine the effects of the Deepwater Horizon oil spill on rates of marsh organic matter decomposition. Decomposition in surface and subsurface marsh sediments was assessed in stands of Spartina alterniflora and Juncus roemerianus in 9 Mississippi Gulf Coast marshes exposed to differing oiling intensities. The cotton strip bioassay technique was used as a proxy for cellulose decomposition. In addition, rates of microbial respiration, fungal biomass (ergosterol) and nutrients (C:N, C:P) of surface sediment cotton strips were also quantified. Subsurface cotton strip decay, as determined by losses in tensile strength, were significantly different among marsh sites, with higher overall rates being observed in oiled versus unoiled S. alterniflora plant zones (pJ. roemerianus plant zones (p>0.05). In contrast to subsurface sediments, cotton strip decay in surface sediments displayed an opposite pattern, with significantly (p>0.05) higher rates of decay in unoiled versus oiled S. alterniflora and J. roemerianus plant zones. Cotton strip C:N and C:P ratios were negatively correlated with losses in cotton strip tensile strength. In addition, both fungal ergosterol concentrations and microbial respiration rates were positively correlated with cotton strip decay and negatively correlated with C:N and C:P ratios, providing evidence that N and P availabilities in marsh sediments may have limited the activity of microbial communities. Although conducted ~1.5 years after the Deep Water Horizon oil spill, this study suggests that both subsurface and surface microbial processes may still be affected by oil.

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