INTERNAL OXYGEN DYNAMICS AND RHIZOSPHERE OXIDATION IN TROPICAL SEAGRASS, THALASSIA TESTUDINUM

Large-scale seagrass mortality events have been linked to internal hypoxia and exposure to phytotoxins in the sediment, such as hydrogen sulfide (H2S). Although seagrasses can transport oxygen (O2) to belowground tissues (rhizomes and roots) and into surrounding sediment to prevent H2S intrusion, reoccurring seagrass mortality events from H2S exposure continue. In the present study, I examined the potential of tropical seagrass Thalassia testudinum to transport O2 effectively to belowground tissues and diffuse O2 into Florida Bay sediment around the root rhizosphere or sediment-root interface to constrain H2S diffusion into the roots. My approach was to (1) examine the spatial distribution of O2 in the rhizosphere during the light and dark with 2-D planar optode sensors, (2) examine patterns of root O2 loss (ROL) with O2 dye tracing experiments, and (3) measure O2 and H2S dynamics in internal tissues and rhizospheres. My results indicate that T. testudinum effectively sustains oxidation in belowground tissues to constrain H2S, but minimal evidence of ROL into the rhizosphere.