Date of Award

Summer 2012

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Chair

Chet Rakocinski

Committee Chair Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 2

Patrick Biber

Committee Member 2 Department

Coastal Sciences, Gulf Coast Research Laboratory

Committee Member 3

Bruce Comyns

Committee Member 3 Department

Coastal Sciences, Gulf Coast Research Laboratory

Abstract

Macrobenthic communities offer effective indicators of biotic integrity, but their use for distinguishing anthropogenic from natural stress is tricky because coastal taxa are eurytolerant. Effective coastal management calls for benthic indicators that respond to specific stressors, apply across different habitats, and reflect ecosystem function. Macrobenthic process metrics based on body-size descriptors should reflect ecosystem function and be useful for assessing the effects of eutrophication. Functional trait analysis should reflect the functional diversity of the community. Coastal Mississippi experienced widespread and sustained hypoxia throughout summer 2008. Site 6 located on the 10-m isobath in the center of the 2008 hypoxic zone and site 8 located on the 20-m isobath near the edge of the zone served as study areas for examining effects of this event. Samples taken in 2008 represented these sites in late spring prior to hypoxia, in mid-summer during severe hypoxia, and in autumn following a return to normoxia. Production potential and total abundance decreased dramatically after May 2008 at site 6. Declines in mean size and community turnover rate were not nearly as pronounced. Normalized biomass-size spectra (NBSS) varied among months of 2008. Prior to hypoxia in May, the NBSS comprised high abundances of organisms distributed across a very broad range of size classes, in July, all size classes were reduced or absent as a likely outcome of hypoxia, and in November, there was some recovery of smaller size classes. Functional trait analysis showed a decline in functional diversity after May 2008 with some recovery by November 2009.

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