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How a stream periphyton metabarcoding nutrient change-point study has informed TMDL development in a Southwestern Ohio watershed
Citation:
Nietch, C., P. Gledhill, N. Smucker, Matthew Heberling, E. Pilgrim, L. Yuan, AND R. Mitchell. How a stream periphyton metabarcoding nutrient change-point study has informed TMDL development in a Southwestern Ohio watershed. 2022 Joint Aquatic Sciences Meeting, Grand Rapids, MI, May 14 - 20, 2022.
Impact/Purpose:
The purpose of this presentation is to demonstrate how better linkages between nutrients and sensitive biotic endpoints can be coupled with solutions driven monitoring and modeling approaches for nutrient reduction planning in small watersheds with impaired streams.
Description:
Linkages between aquatic life impairment and excess nutrients are often difficult to establish to a degree necessary to rationalize concentration and loading targets for reduction and restoration efforts. Data from strategic stream monitoring in the East Fork of the Little Miami River Watershed in Southwest Ohio were used to select sites representing a broad range of nitrogen and phosphorus concentrations. These sites informed the design of a DNA metabarcoding study that characterized spatial and temporal differences in stream periphyton using diatom rbcL and bacterial 16S sequencing. The published study results identified assemblage change points and characterized the relative importance of nitrogen and phosphorus in the system. These nutrient-biota relationships corroborated nutrient targets established using a reference condition approach from the strategic monitoring. Both lines of evidence were used to help rationalize excess nutrients as the source of stream impairment in a loading analysis plan written as a requirement of Ohio’s total maximum daily load (TMDL) program. The targets are now being combined with the application of the Soil and Water Assessment Tool (SWAT) model to develop conceptual near-field nitrogen and phosphorus TMDLs for the subwatersheds whose streams were classified as non-attaining for fish and/or benthic macroinvertebrates in the State’s bioassessment survey. The SWAT output is conditioned to set load allocations and reduction requirements for each subwatershed. The overall effort demonstrates how better linkages between nutrients and sensitive biotic endpoints can be coupled with solutions driven monitoring and modeling approaches for nutrient reduction planning in small watersheds with impaired streams.
