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Thesis
TEMPORAL DIFFERENCES IN NITROGEN FIXATION RATES WITHIN SEDIMENTS COLONIZED BY SUBTROPICAL SEAGRASS SPECIES, THALASSIA TESTUDINUM AND HALODULE WRIGHTII
University of West Florida
Master of Science (MS), University of West Florida
2017
Abstract
Seagrasses are widely distributed across the globe and provide many ecological services. Thalassia testudinum and Halodule wrightii are the dominant taxa in Northwest Florida. Primary productivity in coastal ecosystems is often limited by availability of bioavailable nitrogen. Nitrogen fixation is a microbially mediated process that converts N2 to bioavailable forms. This study measured nitrogen fixation and environmental parameters in unvegetated areas and seagrass colonized sediments for one year. Porewater nutrient ratios in sediments colonized by seagrass suggest that nitrogen is the limiting nutrient. Conversely, unvegetated sediments show phosphorus limitation. Nitrogen fixation rates were higher in vegetated areas compared to adjacent unvegetated areas. In unvegetated sediments, increased mineralization results in increased nutrients and energy sources for sulfate reducing bacteria which fix nitrogen. In H. wrightii colonized sediments, nitrogen fixation was driven by decreased availability of nitrogen relative to phosphorus. In T. testudinum colonized sediments, nitrogen fixation was higher during winter. Organic matter supply may be a controlling factor in all three substrate types albeit the mechanism driving nitrogen fixation is slightly different. During June 2016, July 2016, and September 2016, nitrogen fixation provided 8.5%, 1.0%, and 1.0%, respectively, of T. testudinum nitrogen demand. Annually, nitrogen fixation provides 1.3% and 2.9% of the nitrogen demand for T. testudinum and H. wrightii, respectively. Nitrogen fixation was an important source of nitrogen during periods of senescence and dormancy when organic matter content was higher and seagrasses obtain the majority of their nitrogen from the sediments.
Details
- Title
- TEMPORAL DIFFERENCES IN NITROGEN FIXATION RATES WITHIN SEDIMENTS COLONIZED BY SUBTROPICAL SEAGRASS SPECIES, THALASSIA TESTUDINUM AND HALODULE WRIGHTII
- Resource Type
- Thesis
- Publisher
- University of West Florida
- Format
- text
- Identifiers
- 99380090856206600
- Academic Unit
- Biology
- Language
- English
- Awarding Institution
- University of West Florida; Master of Science (MS)
- Theses and Dissertations
- Master of Science (MS), University of West Florida