Understanding processes involved in the mobilization and transformation of phosphorus (P) in the soil-water continuum requires novel approaches that can that go beyond operationally defined methods and can connect sources, chemical reactivity, and pathways of transformation. We apply HPIC, NMR, and stable isotope methods along with enzymatic assays and molecular microbiological methods and compare results from field transect and controlled experiments to identify dominant sources and processes involved in P cycling in the continuum. Series of studies undertaken in an agriculture-runoff dominated catchment suggest that phytate is the dominant source of organic P. Abundance of bacteria capable of phytate degradation and expression of phytase gene indicate that the presence of phytate promotes the proliferation of phytate-degrading microorganisms. Laboratory incubation studies reveal that different enzymes generate largely distinct sets of isomers and phosphate moieties in phytate are isotopically identical- proving a new tool to track the sources of P in downstream waters. Based on isotope composition and fingerprinting elements at source sites, agricultural field soils, streambank materials, and sediments are found to contribute downstream P but at variable proportions. While greater scrutiny is required to connect results from different methods and generalize for the field conditions, our results, nonetheless, provide an improved understanding of the sources and biogeochemical processes impacting downstream water quality and point towards particular sources as major culprits for water quality.

Linking sources and transformation of phosphorus in the soil-water continuum in the estuarine environment

255th National Meeting (2018)

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