Oyster reefs are increasingly used to protect estuarine shorelines from erosion. These reefs can grow vertically over time, helping them keep pace with sea-level rise and maintain their ability to reduce wave energy. However, reefs can also grow laterally, potentially expanding their protective benefits along the shoreline. Most restoration projects build reefs parallel to the shoreline, but natural reefs often grow in long, narrow shapes that extend outward, perpendicular to shorelines and tidal flow. The processes behind this natural growth pattern are not well understood.

To explore how natural reefs grow, we studied three fringing oyster reefs in North Carolina U.S.A. using sediment cores, shell and sediment analysis, and radiocarbon dating. We found that reefs typically began growing in the intertidal zone and expanded outward, with the edges often starting subtidally and accreting upward. Each reef responded differently to environmental stress. One degraded due to increased mud from land use changes, another remained productive thanks to strong tidal flushing, and a third recovered from repeated storm impacts.

These findings show that natural reefs can expand and persist under various conditions but are sensitive to excess fine sediment. Understanding these dynamics can guide more resilient and effective reef restoration designs.