Controls of Suspended Sediment Concentration, Nutrient Content, and Transport in a Subtropical Wetland
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Redistribution of largely organic sediment from low elevation sloughs to higher elevation ridges is a leading hypothesis for the formation and maintenance of the native ridge and slough landscape pattern found in peat wetlands of the Florida Everglades. We tested this redistribution hypothesis by measuring the concentration and characteristics of suspended sediment and its associated nutrients in the flowpaths of adjacent ridge and slough plant communities. Over two wet seasons we found no sustained differences in suspended sediment mass concentrations, particle-associated P and N concentrations, or sizes of suspended particles between ridge and slough sites. Discharge of suspended sediment, particulate nutrients, and solutes were nearly double in the slough flowpath compared to the ridge flowpath due solely to deeper and faster water flow in sloughs. Spatial and temporal variations in suspended sediment were not related to water velocity, consistent with a hypothesis that the critical sheer stress causing entrainment is not commonly exceeded in the present-day managed Everglades. The uniformity in the concentrations and characteristics of suspended sediment at our research site suggests that sediment and particulate nutrient redistribution between ridges and sloughs does not occur, or rarely occurs, in the modern Everglades.
KeywordsEntrainment Everglades Nitrogen Particle Phosphorus
We thank Dan Nowacki, Jennifer O’Reilly, Ami Riscassi, Joel Detty, and Leanna Westfall for their assistance with field and laboratory work, and Forrest Dierberg, Kurt Kowalski, and anonymous reviewers for their valuable comments on an earlier draft of this manuscript. This work was funded by the Everglades Priority Ecosystem Science Program and National Research Program of the USGS and a Canon National Parks Science Scholarship to LGL. Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government.
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