Doyle, Robert D. (Robert Donald)Scott, J. Thad (Jefferson Thad).Baylor University. Dept. of Biology.2007-08-212007-08-2120062005Scott JT, Doyle RD, Filstrup CT (2005) Periphyton nutrient limitation and N2 fixation potential along a wetland nutrient depletion gradient. Wetlands 25: 439-448Scott JT, Doyle RD (2006) Coupled photosynthesis and heterotrophic bacterial biomass production in a nutrient-limited wetland periphyton mat. Aquatic microbial ecology 45: 69-77http://hdl.handle.net/2104/5036Includes bibliographical references (p. 105-114).In this study, the factors influencing the development of a nutrient availability gradient in a wetland ecosystem and the subsequent controls to, and feedbacks from, the structure and function of the periphyton community were investigated. Field surveys, field experiments, and a laboratory experiments were conducted over a three year period in the Lake Waco Wetlands, a created wetland system near Waco, Texas. Results of these studies indicated that nitrogen (N) retention/removal always exceeded phosphorus (P) retention/removal along the flow path of water. Over 90% of nitrate (NO3-) entering the wetland was generally retained by the system and 50% of that retention was a result of influx into sediments. Intact sediment core experiments revealed that virtually all available NO3- in the sediments was denitrified. Inorganic P entering the wetland was less well retained (up to 50%), but the wetland was sometimes a source of P as well. The disproportionate loss of inorganic N resulted in a distinct gradient of nutrient availability where N was relatively more abundant near the inflow, but became decreasingly less abundant than P as distance from the inflow increased. Experimental N and P enrichments at the inflow often resulted in an increase in periphyton biomass accumulation. However, only N alone stimulated biomass accumulation in downstream areas. Floating periphyton mats, or "metaphyton", appeared to overcome N deficiency on a seasonal basis by fixing, and efficiently retaining, large quantities of atmospheric N2. In fact, average N-specific metaphyton production throughout the entire wetland was inversely correlated with average metaphyton phosphatase activity (r2 = 0.78; p = 0.0015). These results suggest that fixed N2 may supply a sufficient quantity of N to offset periphyton N limitation and initiate P limitation. The response to inorganic N additions is maintained because use of NO3--N is less energetically expensive to utilize than N2. Furthermore, results of laboratory experiments suggest that some mechanisms may exist by which bacteria and photoautotrophs compensate the supply of P and fixed N2, respectively, to one another within the community.xi, 114 p. : ill.48951 bytes1461637 bytesapplication/pdfapplication/pdfen-USBaylor University theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. Contact librarywebmaster@baylor.edu for inquiries about permission.Constructed wetlands --- Texas --- Waco - Case studies.Bacteria, Denitrifying.Water -- Purification -- Phosphate removal.ThesisWorldwide access