Drivers of legacy phosphorus release and sequestration in sediment-water systems: insights from environmental monitoring and experimental manipulation of redox front dynamics
Abstract
Linkages between sediment-water interface (SWI) geochemistry, redox dynamics, and legacy phosphorus behavior are critical to understanding and managing eutrophication and cyanobacteria blooms in shallow lakes, where benthic fluxes can be dominant micro and macronutrient sources in the euphotic zone. At shallow eutrophic sites in Vermont's Lake Champlain, we have demonstrated that the release and sequestration of legacy phosphorus, as well as associated algal dynamics, are often driven by fluctuations in the position of the redox front relative to the SWI. However, this varies in both time and space. Here, through analysis of time series water column and sediment chemistry, coupled with experimental manipulation of SWI redox conditions in mesocosm experiments, we explore the relationship between environmental drivers(e.g. water column stability, riverine input, seasonality, biological production, ice cover), SWI redox front position, and the chemical partitioning of legacy P in sediment and overlying bottom water. Our comprehensive analysis demonstrates that partitioning and release or sequestration of legacy P in these sediment-water systems is highly dynamic and sensitive to an array of chemical, physical, and biological drivers of geochemical conditions across the SWI. Furthermore, linkages between the redox driven cycling of Fe and legacy P mobility and speciation are similarly variable. Lake management initiatives aimed at reducing phosphorus loading from legacy sediment pools or suppressing consequent potentially harmful cyanobacteria blooms must therefore consider dynamic and potentially site specific combinations of internal and external processes impacting the SWI geochemistry. Such dynamics in turn drive sediment legacy P concentration, composition, and mobility. Furthermore, models that seek to project changes in the behavior and distribution of legacy phosphorus must also capture such dynamics using appropriate geochemical monitoring data.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H33J2055S
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1831 Groundwater quality;
- HYDROLOGY;
- 1834 Human impacts;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY