What’s mud got to do with it?: Sediment internal nutrient supply and sequestration in Sandusky Bay

Session: Beyond the Edge of the Field: Mitigating the Impacts of Nutrient Pollution on HABs (3)

Lauren Kinsman-Costello, Kent State University, [email protected]
Bree Richardson, Kent State University, [email protected]
Laura Johnson, Heidelberg University, National Ctr for Water Quality Res., [email protected]
George Bullerjahn, Bowling Green State University, [email protected]

Abstract

Coastal bays provide ecosystem services, and often sit at a critical interface between watershed nutrient sources and water bodies vulnerable to Harmful Algal Blooms (HAB). Lake Erie’s Sandusky Bay (OH) consistently experiences severe HABs that threaten the well-being of surrounding communities. External nutrient loads unquestionably support HABs, but sediments may internally supply or sequester nutrients. Understanding sediment contribution to Sandusky Bay nutrient cycling is critical to implementing effective management and restoration. To support large-scale Sandusky Bay Initiative restoration, we measured sediment geochemistry, including comprehensive fractionation of phosphorus (P) forms, and experimentally estimated nutrient exchange rates between sediments and surface waters under environmentally relevant conditions. Sediment P content declined along the land-to-lake flowpath, with more P stored in sediments closest to the mouth of the Sandusky River, and declining total P at sites in the outer bay, closest to exchange with Lake Erie. Although distribution of P forms varied, all sediments had a high capacity to store P under high surface water P, oxic conditions. Some sediments, however, released P when conditions were anoxic and/or surface water P concentrations were lower. Continued understanding of sediment nutrient transformation, storage, and release mechanisms is critical for HAB mitigation efforts.