Improved Understanding of a Valuable Ecosystem Service: Analysis of 15 Years of Oyster-Mediated Denitrification Experiments

Oysters are vital to fisheries, shoreline stabilization, and water quality. By enhancing sediment denitrification, the microbial conversion of bioavailable nitrogen into inert dinitrogen gas (N2), oysters reduce eutrophication and harmful algal blooms. With ~90% of natural reefs depleted globally, restoration and aquaculture are promising nature-based solutions. Yet, regional-scale assessments of oyster-mediated denitrification (OMD) remain limited. This study leverages 15 years of experiments quantifying summertime OMD in oyster reef and adjacent flat habitats across coastal North Carolina. OMD was assessed across management contexts (natural, restored, culture) and environmental conditions (tidal position, sediment characteristics, watershed nitrogen loading). Regionally, reefs exhibited higher OMD than flats. OMD was similar among reef types, though restored and culture reefs demonstrated higher denitrification efficiencies than natural reefs. At the sub-watershed scale, OMD was strongly associated with anthropogenic nitrogen loading. This study establishes reef restoration and aquaculture as effective nature-based solutions for maintaining water quality and coastal resilience.