2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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5/26/2021 | 8:30 AM - 10:30 AM | DOES CHANGING LAND COVER ALTER N:P:SI RATIOS AND RISK FOR CYANOBACTERIAL BLOOMS IN STREAMS DRAINING INTENSIVE AGRICULTURE? | Virtual Platform

DOES CHANGING LAND COVER ALTER N:P:SI RATIOS AND RISK FOR CYANOBACTERIAL BLOOMS IN STREAMS DRAINING INTENSIVE AGRICULTURE?

Agricultural streams often have a stoichiometric imbalance among nitrogen (N), phosphorus (P), and silicon (Si) which can contribute to the development of harmful algae blooms (HABs). Planting winter cover crops can retain N and P on the landscape, yet their effect on Si concentrations and stoichiometry is unknown. We analyzed three years of biweekly concentrations and loads of dissolved N, P, and Si in subsurface tile drains and stream water in two agricultural watersheds in northern Indiana. There was no significant difference in tile drain Si concentrations between fields with and without cover crops, although there were distinct seasonal patterns. Average tile drain Si concentrations (as SiO2) ranged between 7-12 mg/L with a mean value of 9 mg/L during the period of record. Comparatively, inorganic N and P concentrations varied over multiple orders of magnitude. To assess the risk of HAB formation, we calculated a stoichiometric index to quantify potential for non-siliceous algal growth facilitated by excess N and P relative to Si. Results show low potential for HABs during summer despite frequent summer HABs in surface waters, suggesting stoichiometric imbalances are not the sole driver of summer HABs.

Biogeochemistry
Nutrients
Conservation

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Presenters/Authors

Lienne Sethna (), Indiana University, lsethna@iu.edu;