title: Laboratory-determined phosphorus flux from lake sediments as a measure of internal phosphorus loading.
abstract: Eutrophication is a water quality issue in lakes worldwide, and there is a critical need to identify and control nutrient sources. Internal phosphorus (P) loading from lake sediments can account for a substantial portion of the total P load in eutrophic, and some mesotrophic, lakes. Laboratory determination of P release rates from sediment cores is one approach for determining the role of internal P loading and guiding management decisions. Two principal alternatives to experimental determination of sediment P release exist for estimating internal load: in situ measurements of changes in hypolimnetic P over time and P mass balance. The experimental approach using laboratory-based sediment incubations to quantify internal P load is a direct method, making it a valuable tool for lake management and restoration. Laboratory incubations of sediment cores can help determine the relative importance of internal vs. external P loads, as well as be used to answer a variety of lake management and research questions. We illustrate the use of sediment core incubations to assess the effectiveness of an aluminum sulfate (alum) treatment for reducing sediment P release. Other research questions that can be investigated using this approach include the effects of sediment resuspension and bioturbation on P release. The approach also has limitations. Assumptions must be made with respect to: extrapolating results from sediment cores to the entire lake; deciding over what time periods to measure nutrient release; and addressing possible core tube artifacts. A comprehensive dissolved oxygen monitoring strategy to assess temporal and spatial redox status in the lake provides greater confidence in annual P loads estimated from sediment core incubations.
authors.affiliation: Annis Water Resources Institute, Grand Valley State University; ogdahlm@gvsu.edu.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Ogdahl
authors.affiliation: Annis Water Resources Institute, Grand Valley State University.
authors.forename: Alan D
authors.initials: AD
authors.lastname: Steinman
authors.affiliation: Annis Water Resources Institute, Grand Valley State University.
authors.forename: Maggie E
authors.initials: ME
authors.lastname: Weinert
mesh_terms: D000534:Alum Compounds / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry*; D060106:Lakes; D010758:Phosphorus / Q000032:analysis*
chemical_list: D000534:Alum Compounds; D010758:Phosphorus; C041524:aluminum sulfate