Year of Publication

2011

Season of Publication

Fall

Paper Type

Master's Thesis

College

College of Arts and Sciences

Degree Name

Master of Arts in Biology (MA)

Department

Biology

First Advisor

Dr. Cliff Ross

Second Advisor

Dr. Daniel C. Moon

Third Advisor

Dr. Amy Lane

Department Chair

Dr. Courtney T. Hackney

College Dean

Dr. Barbara A. Hetrick

Abstract

Seagrass meadows are essential to coastal ecosystems and have experienced declines in abundance due to a series of environmental stressors including elevated salinity and incidence of disease caused by the pathogen Labyrinthula sp. This thesis evaluated the dynamics between T. testudinum and Labyrinthula concerning the impacts of short term elevated salinity stress on the early stages of infection in Thalassia testudinum (Chapter 2) as well as the presence of anti-labyrinthulid secondary metabolites produced by the tropical seagrass (Chapter 3). The results showed that short term exposure to hypersalinity alters some cellular processes but does not necessarily lead to an immediate increase in wasting disease susceptibility. Specifically, the occurrence of disease was significantly lower in the hypersalinity treatments possibly due to a direct osmotic shock to Labyrinthula or indirectly due to the increase in in vivo H2O2 concentrations that may have inhibited Labyrinthula growth. In addition, it was shown that 4 phenolic acids commonly found in turtlegrass leaf tissue were able to inhibit Labyrinthula growth in culture. Using a bioassay-guided fractionation technique, several purified fractions of T. testudinum leaf tissue showed anti-labyrinthulid activity, however the detailed characterization of the unknown compounds was inconclusive. The results presented in this thesis highlight the halotolerant characteristics of the seagrass T. testudinum as well as suggest that T. testudinum has the capability of defending itself against Labyrinthula infection using secondary metabolites.

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