Phosphate is strongly sorbed to nanoparticulate iron and manganese oxides in freshwater lake sediments, often controlling the availability of inorganic and organic phosphorus to microorganisms in the water column.  In a shallow freshwater system in northern Lake Champlain, we have established that these oxide minerals are sensitive to changing redox chemistry near the sediment water interface (SWI) over both seasonal and diel time frames (Smith et al., 2011).  Recent mesocosm experiments have shown that changes to the redox environment at the SWI over very short time intervals (minutes to hours) can change the degree and direction of phosphate flux across the SWI. Field evidence and modeling has additionally shown that cyanobacterial blooms themselves stimulate the most reducing conditions at the SWI, setting up a positive feedback loop that may be integral to the propagation and sustenance of the blooms, if not the triggering mechanism that starts harmful algal bloom activity.

Dynamic redox oscillations in freshwater lake sediments driving phosphate flux through iron and manganese oxide transformations

245th National Meeting (2013)

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