Abstract
Oyster reefs are often touted for their contribution to water quality improvement, shoreline protection, and habitat creation, but few studies highlight another significant ecosystem service: organic carbon (OC) storage and cycling. Although oyster reefs may not fall within the definition of “blue carbon” as a vegetated coastal ecosystem, they may store as much carbon (C) as other well‐studied coastal C sinks (e.g., mangroves, salt marshes, and sea grasses), providing an additional justification for restoration activities. Leveraging ongoing Crassostrea virginica reef restoration in Mosquito Lagoon, Florida (USA), this study employed a Before‐After‐Control‐Impact sampling design to evaluate short‐term (1 yr) changes in sediment OC storage and flux, microbial activity, and microbial community composition on degraded, natural, and restored oyster reefs. Restored reefs exhibited the greatest change in OC cycling within the study year, with increases in dissolved OC (31%), particulate OC (97%), CO 2 flux (707%), and β‐glucosidase enzyme activity (467%), resulting in the highest total C and OC concentrations of the three reef types. Results demonstrate that sediment microbial community abundances are resilient and easily reinvigorated through reef restoration, while enzyme assays suggest sediment microbial activity on restored reefs may be limited by labile C availability. Overall, this study suggests restoration and oyster presence can rapidly enhance OC storage and can help offset the C flux from high calcification rates on young oyster reefs, providing an additional ecosystem service to support the importance of restoration activities.