Type of Document Dissertation Author Bass, Aaron Stuard Author's Email Address email@example.com URN etd-01282004-133655 Title Application of Disturbance Theory to Assess Impacts Associated with a Three-Dimensional Seismic Survey in a Freshwater Marsh in Southwest Louisiana Degree Doctor of Philosophy (Ph.D.) Department Oceanography & Coastal Sciences Advisory Committee
Advisor Name Title R. Eugene Turner Committee Chair G. Bruce Williamson Committee Member Hamady Diop Committee Member Irving A. Mendelssohn Committee Member Lawrence J. Rouse, Jr. Committee Member Richard E. Condrey Committee Member Phillip J. Bart Dean's Representative Keywords
- wetland disturbance
- oil and gas impacts
- disturbance ecology
- wetland management
- seismic surveys
Date of Defense 2003-11-04 Availability unrestricted AbstractThis study examined various practical and theoretical aspects of disturbance in a coastal wetland marsh in southern Louisiana. A literature review approached disturbance ecology from both practical and theoretical perspectives and assessed its applicability to developing broad predictive models. However, specific knowledge of environmental variables, competitive relationships, and the interactive effects of multiple disturbances are required for meaningful usage of these models.
The Lacassine National Wildlife Refuge (LNWR) proved to be an ideal laboratory to test various aspects of ecological disturbance theory. I found that the primary disturbances affecting the LNWR have been hurricanes, droughts, water-level manipulations, prescribed burning, oil and gas recovery activities, grazing by Myocastor coypus (nutria), and managed cattle grazing.
The 1990's application of three-dimensional (3-D) seismic technology used in the oil and gas recovery business challenged landowners, government regulators, and industry to develop ways to recover these resources without damaging surface features. I developed a conservative estimate that an area exceeding 2.5 times the area of Louisiana's coastal wetlands was covered by overlapping seismic surveys in southern Louisiana from 1997 through 2002, equal to 22.5 km2/year. I provided a general overview of 3-D seismic survey programs, potential adverse impacts, and management and restoration strategies. I also conducted a field study at the LNWR on vegetation in control and treatment transects before, and for two years after, a 3-D survey.
I found vegetative cover and the amount of dead plant biomass were significantly lower in treatment plots, but live biomass was not different in treatment and control plots. Species richness was higher in treatment plots compared to control plots, but the live biomass and cover of the dominant species (Panicum hemitomon) was lower. The live biomass and cover of Eleocharis spp., a colonizing species, was greater in treatment plots compared to control plots. There was no significant effect of equipment type or traffic level within treatment plots for total live cover, total live biomass, or total dead biomass. Clear trends of the disturbance effects across disturbance types and habitats were not revealed. Furthermore, extrapolating the effects of a disturbance using the available general concepts should be done with caution because of the overriding influence of the site and species on disturbance effects.
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