Progress 09/01/04 to 08/31/07
Outputs
OUTPUTS: The role that biological processing and sequestration plays in the phosphorus (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 study 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. 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. 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. 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, the information derived by the study of a range of wetlands helped 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. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Anthropogenic alteration of global P cycling has been profound, and given expected global population and consumption growth we are likely to see the continued and increased impacts of a disrupted P cycling on natural ecosystems. Due to their position in the landscape wetlands are often a focus of this disruption, with many wetlands showing a degradation or shift in ecosystem function due to P loading. This study provides a basic understanding of phosphorus pools and stability in a range of wetlands in the United States. Results of this provides information on the stability of phosphorus stored in wetlands and can be used my managers to determine the role of wetlands in improving water quality.
Publications
- Cheesman, A. W., B. L. Turner, P. W. Inglett, and K. R. Reddy. 2010. Phosphorus transformations during decomposition of wetland macrophytes. Environmental Science and Technology 44:9265-9271.
- Cheesman A. W., B. L. Turner, and K. R. Reddy. 2010. Interaction of phosphorus compounds with anion-exchange membranes: Implications for soil analysis. Soil Science Society of America Journal 74:1607-1612.
- Cheesman A. W., E. J. Dunne, B. L. Turner, and K. R. Reddy. 2010. Soil phosphorus forms in hydrologically isolated wetlands and surrounding pasture uplands. Journal of Environmental Quality. 39:1517-1525.
- Cheesman, A. 2010. Biogenic phosphorus in palustrine wetlands:Sources and stabilization. Ph.D. Dissertation. University of Florida.
- Turner, B. L.,S. Newman, A. W. Cheesman, and K. R. Reddy. 2007. Sample pretreatment and phosphorus speciation in wetland soils. Soil Science Society of America Journal. 71:1538-1546.
- Cheesman, A. W., J. Rocca, and B. L. Turner. 2012. Phosphorus characterization in wetland soils by solution 31P nuclear magnetic resonance (NMR) spectroscopy. In: Biogeochemistry of Wetlands, edited by R. DeLaune, P. Megonigal, and K.R. Reddy. American Society of Agronomy, Madison, WI (submitted).
- Cheesman, A. W., B. L. Turner, and K. R. Reddy. 2011. Phosphorus forms and dynamics in a tropical ombrotrophic wetland. Ecosystems (submitted).
- Sjogersten S, A. W. Cheesman, O. Lopez, and B. L. Turner. 2011. Biogeochemical processes along a nutrient gradient in a tropical ombrotrophic peatland. Biogeochemistry (in press).
- Wright, E., C. R. Black, A. W. Cheesman, T. Drage, D. Large, B. L. Turner, and S. Sjogersten. 2011. Contribution of subsurface peat to CO2 and CH4 fluxes in a neotropical peatland. Global Change Biology (in press).
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Progress 10/01/05 to 09/30/06
Outputs
Wetlands sequester phosphorus from polluted runoff in organic forms, yet the long-term stability of organic phosphorus in wetland soils remains poorly understood. Initial studies within Florida wetlands have demonstrated an abundance of what are routinely thought of as unstable organic phosphates, raising concerns over the long-term efficacy of treatment wetlands. As a result we are utilizing phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy and anion exchange membranes (AEM) to determine the nature and availability of organic phosphorus in a range of wetlands from the continental Americas. To date, eighteen non-riverine wetlands have been sampled across a hydrogeomorphic and geographical range. Sample wetlands characterized for hydrology, vegetation type, and degree of anthropogenic impact have been selected to achieve coverage of a wide spectrum of characteristics and will be supplemented by additional sites in the spring of 2007. Sampled soil
characterization includes: regular analyses for pH, Total Metals, Carbon, and Nitrogen, as well as the application of AEM and NMR spectroscopy. A developed methodology coupling AEM and 31P solution NMR allows for the determination not only of functional groups present within the soil, but also the "bioavailability" of phosphorus from identified pools. This, coupled with investigations of carbon forms present within archived samples (via solid state 13C NMR), will yield critical information on the sequestration of phosphorus in relation to various wetland parameters. Although definitive conclusions must await the completion of all analyses and appropriate multivariate statistical analysis, a number of tentative results can be seen; in particular that, to date, inositol phosphates (a major component of upland systems) have yet to be identified within sampled wetlands, and that the use of exchange membranes offers a robust and defendable analogue to bioavailability, which, in concert
with NMR, provides a means of establishing the biological relevance of identified organic phosphorus forms.
Impacts
Often wetlands are viewed as sinks for phosphorus, because of their capacity to transform inorganic phosphate into organic phosphorus pools. However, this does not guarantee acceptable water quality. The critical question is not just how much phosphorus is stored in a wetland, but what is its relative bioavailability, stability, and long-term influence on surface water quality. Results of this project will determine the stability of organic P in a range of wetlands.
Publications
- Turner B. L, S.Newman, K. R.Reddy. 2006. Overestimation of organic phosphorus in wetland soils by alkaline extraction and molybdate colorimetry ENVIRONMENTAL SCIENCE & TECHNOLOGY 40 (10): 3349-3354.
- Turner, B. L., S. Neweman, and J. M. Newman. 2006. Organic phosphorus sequestration in subtropical treatment wetlands. Environ. Sci. Technol. 40:727-733.
- Inglett PW, and K. R. Reddy. 2006. Investigating the use of macrophyte stable C and N isotopic ratios as indicators of wetland eutrophication: Patterns in the P-affected Everglades . LIMNOLOGY AND OCEANOGRAPHY 51 (5): 2380-2387.
- Corstanje R, and K. R. Reddy. 2006. Microbial indicators of nutrient enrichment: A mesocosm study . SOIL SCIENCE SOCIETY OF AMERICA JOURNAL 70 (5): 1652-1661.
- Sharma K, Inglett PW, Reddy KR, Ogram AV. 2005. Microscopic examination of photoautotrophic and phosphatase-producing organisms in phosphorus-limited Everglades periphyton mats. LIMNOLOGY AND OCEANOGRAPHY 50 (6): 2057-2062.
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Progress 10/01/04 to 09/30/05
Outputs
Information on the long-term stability of sequestered phosphorus in wetlands clearly represents a fundamental knowledge gap in our understanding of wetland ecosystems, which undermines our ability to predict their long-term effectiveness in remediating diffuse pollution. We propose to address this by investigating the organic phosphorus and carbon composition of a wide range of wetland soils using state-of-the-art NMR spectroscopy. Through this organic matter fingerprinting, we will test the hypothesis that the long-term sequestration of organic phosphorus in wetlands depends on changes in nutrient status and hydrological regime. Specifically, we will address the following key research questions: (1) Which forms of phosphorus exist in wetland soils?, (2) What is the long-term stability of these compounds?, (3) How is stable organic phosphorus linked to organic matter structures?, and (4) How is phosphorus sequestration and retention influenced by changes in nutrient
status and hydrological regime?. For natural wetlands within or adjacent to agricultural watersheds, the wetland sites slected include riparian wetlands, bottomland hardwood forested wetlands, prairie potholes, isolated wetlands, and coastal wetlands. Up to 10 sites are selected from different states, including Alaska, California, Florida, Georgia, North Carolina, New York, Indiana, Iowa, and Louisiana. Criteria for selection of natural wetland sites will be based on soil characteristics, vegetation, water quality data, and position on the landscape (i.e., access to the site). Constructed wetlands selected include up to 5 sites used for several years to treat various agricultural effluents, including swine lagoon effluents (North Carolina), poultry effluents (Arkansas), dairy effluents (Florida), agricultural drainage effluents (Florida), municipal effluents (Michigan). Criteria for selection of constructed wetland sites will be based on the history of phosphorus loading and the
availability of long-term water quality data. Soil samples will characterized for various organic P forms using traditional chemical fractionation schemes and P-31 NMR techniques.
Impacts
Often wetlands are viewed as sinks for phosphorus, because of their capacity to transform inorganic phosphate into organic phosphorus pools. However, this does not guarantee acceptable water quality. The critical question is not just how much phosphorus is stored in a wetland, but what is its relative bioavailability, stability, and long-term influence on surface water quality. Results of this project will determine the stability of organic P in a range of wetlands.
Publications
- Turner, B. L and S. Newman. 2005. Phosphorus cycling in wetland soils: The importance of phosphate diesters. J. Environ. Quality. 34:1921-1929.
- Turner, B. L., S. Newman, and J. M. Newman. 2005. Organic phosphorus sequestration in subtropical wetlands. Environ. Sci. Technol. (in press).
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