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Master of Science (MS)
Sulfide toxicity is implicated in seagrass declines worldwide. Studies examining the relationship between seagrass presence and sulfide concentrations have yielded conflicting results. Interpretation of the seagrass-sulfide relationship is complicated due to the opposing effects of the root system which can increase sulfide oxidation and the burial of organic matter from the plant itself which can increase sulfide production. To quantify the impact of eelgrass leaf detritus and the Zostera marina rhizosphere on pore-water sulfide concentrations, field samples of pore-water sulfide were collected in areas with and without eelgrass. To decouple the effects of live versus dead eelgrass tissue, laboratory studies were conducted over 4 weeks using 10 aquaria with or without eelgrass shoots and 0-8 pieces of Z. marina detritus located at 4 cm and 11 cm depth. Diffusive Gradients in Thin-Films (DGTs) were used to obtain 2D visualizations of sulfide concentrations within the sediment in relation to location of eelgrass detritus and the rhizosphere. In the field study, the presence of leaf detritus accounted for higher than average sulfide concentrations in the sediment. In the laboratory study, the presence of live eelgrass shoots resulted in higher overall sulfide concentrations compared to aquaria without eelgrass. Sulfide concentrations increased with higher mass of added detritus compared to locations where no detritus was added. Sediment within the rhizosphere exhibited reduced sulfide concentrations compared sediment outside the rhizosphere. It is likely that seagrasses are simultaneously increasing and decreasing sulfide concentrations depending on the location analyzed relative to the rhizosphere or buried eelgrass detritus.
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Simpson, Alexandra G. (Alexandra Garcia), "Effects of Zostera marina Roots and Leaf Detritus on the Concentration and Distribution of Pore-Water Sulfide in Marine Sediments" (2016). WWU Masters Thesis Collection. 540.