Biogenic phosphorus in palustrine wetlands: Sources and stabilization

Nutrient pollution, from both diffuse agricultural applications and point source contamination is a pressing concern for ecosystem integrity across the globe. Of particular concern, given the historical precedence of industrialization within the US, is that of phosphorus (P) pollution. Wetlands are both a victim and potential solution of this. Oligotrophic systems are suffering fundamental shifts in ecosystem functioning at the same time that constructed wetlands are being touted for their remediation value.;The role that biological processing and sequestration plays in the P cycle of wetlands has long been recognized, yet it is only recently that analytical techniques have emerged that allow us to probe the functional nature and stability of these P forms in environmental samples. The nature of P functional groups has immediate and profound implications on the interaction and fate of P in the environment, from determining susceptibility to enzymatic and abiotic hydrolysis, to dictating long-term stabilization. Therefore, this dissertation has sought to provide an advance in our understanding of biogenic P in wetland soils by first reviewing the current science and then applying 31P nuclear magnetic resonance (NMR) spectroscopy to investigate the composition and mechanisms that determine that composition in wetland systems.;Initial studies focused on the surveying of P composition in a broad range of palustrine wetland soils. This work not only showed the range of P forms found within wetland soils (e.g. phosphonates, phosphomonoesters (including inositol phosphates), phosphodiesters and long chain inorganic polyphosphates) but highlighted basic wetland properties that appear to impact P composition. Landscape position, vegetation and climate were shown to have little direct influence on P composition while biogeochemical characteristic such as; pH, organic matter content, and nutrient availability (themselves a product of wetland setting) appeared to be linked directly to the P composition of surface soils. Subsequent chapters sought to explore the mechanistic role of these biogeochemical characteristics on determining soil P composition.;The trend, observed between wetlands, that soils with a higher organic matter content had a higher proportion of P found as phosphodiesters was explored by comparison of soils across a landscape continuum. By comparing P composition of soils under similar vegetation and management histories across the wetland-upland transition, the mechanistic role of organic matter content in isolation was investigated. In the wetlands studied, depressional systems within an agricultural landscape north of Lake Okeechobee Florida, P composition was shown to be independent of landscape position and organic matter content. This was unexpected, but believed to be the result of the unique role organic matter plays in the P dynamics of the sandy, low P binding capacity soils of the region. This lack of distinction in the P composition associated with organic matter across a landscape transition was also seen in a study established to determine the redox sensitivity of certain P forms. In this mesocosm study, there was no substantial difference in the turnover rates of DNA and the phosphomonoester myo-Inositol hexakisphosphate (myo-IP6) when considering their presence in a highly organic freshwater system.;The role of microbial processing of soil organic matter in response to environmental conditions, specifically P availability, was determined by tracking the transformations of P forms within detrital organic matter entering a wetland system and by monitoring P composition in surficial soils across a profound nutrient gradient. In both cases it was apparent that P composition was independent of the major allochthonous inputs and represented P forms derived as a result of in-situ microbial processing of organic matter in direct response to environmental conditions.;In conclusion, I use information derived by the study of a range of palustrine systems to develop a working model of biogenic P sources and stabilization in wetlands. This provides not only a significant advance in our understanding of P composition and cycling in wetlands but also provides insite into the biological processes associated with the P cycle of both wetland and terrestrial ecosystems.