Nutrient pollution in coastal ecosystems causes habitat degradation termed eutrophication. Nutrients fuel water column algal blooms which sink to the sediments, decompose, and recycle nutrients back to the water column where they enhance further algal blooms. Continued recycling of nutrients between sediments and overlying water supports chronic eutrophication. The proposed research investigates how microscopic sediment-dwelling algae might attenuate this recycling. The investigators hypothesize that sediment microalgae regulate water quality by intercepting (capping) sediment-water nutrient exchange. The proposal investigates how the cap functions, its efficiency, what causes the cap to fail in eutrophied systems, and how it can be restored. Investigators propose a unique suite of chemical tracers applied in field and laboratory experiments to answer these questions. The work focuses on pristine and eutrophied Mid-Atlantic habitats. This research will provide a better understanding of coastal ecosystem function, and improve predictions of habitat response to human perturbation and/or restoration efforts. Work of this nature is essential for identifying habitats susceptible to human disturbance, and establishing regulatory targets for nutrient loading. Broader impacts of the work include extensive educational components and public outreach. Investigators will mentor high school and undergraduate students, train graduate students, and provide opportunities for traditionally underrepresented groups. The research integrates participation of citizen groups, and creates a public forum for disseminating information. In total, this effort facilitates enhanced stewardship of coastal resources.