Excessive Loading of Sediment and Nutrients Verification Monitoring in St Louis River Bays


Diatom-inferred (DI) total phosphorus concentrations (TP) from sediment core analyses (Alexson 2016) indicated that TP in sheltered SLRE bays exceed the TP goal for the SLRE (30 ug/l). The three sheltered bays sampled were North Bay (MN), Pokegama Bay (WI), and Allouez Bay(WI). Efforts to remove the beneficial use impairment (BUI) for nutrients and sediment for the SLRE will require a further assessment of these bays, and may require the development of site specific goals. Both water quality and biological community data will be useful for identifying site specific goals. There is currently limited data available for the two Wisconsin bays. Three bays in Wisconsin are proposed for additional monitoring – Pokegama, Allouez, and Kimball’s Bay. Monitoring of Kimball’s Bay will provide data on this sheltered bay and may allow useful comparisons to the other two bays being monitored.

Study Design

Proposed Work: Summarized monitoring components include: - Water column nutrient, suspended solids, chlorophyll, and algal species (May-Oct). - Water column profile data (D.O., pH, temp, cond., turbidity) - Near-bottom TP, DP, and NH3 samples to assess sediment nutrient release (upper Pokegama Bay has been observed to have low D.O. concentrations at times) - Sediment analysis – particle size, solids, nutrients - Biological community assessment – fish, benthic macroinvertebrates, near-shore macroinvertebrates (recent macrophytes surveys are available for Allouez Bay (2008) and Pokegama Bay (2009) - Tributary stream monitoring for TP, TKN, NH3, NO3+2, TSS, Fe, and BOD (May-Oct); plus field parameters (D.O., pH, temp, cond., turbidity) ; Pokegama River flow data from USGS will be used to examine load distribution.

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