Short-term hydro-sediment dynamics govern reef restoration success in temperate marginal seas

Temperate marginal seas once hosted extensive flat oyster reefs that sustained biodiversity and ecosystem functioning but have lost more than 97% of their extent. Restoring these habitats remains limited by the lack of a quantitative understanding of the physical boundaries for reef persistence. Here, we addressed this gap through a pioneering restoration experiment in the 32-m-deep North Sea, combining in situ and mesocosm studies to identify critical thresholds. We found that the establishment of reintroduced oysters is governed by distinct dislodgement and burial thresholds, with short-term hydro-sediment dynamics outweighing long-term water quality as the primary drivers of restoration outcomes. Building on these thresholds, we assessed restoration feasibility across European marginal seas, revealing spatially explicit opportunities and informing risk-based strategy design. This study underscores the need to incorporate short-term hydro-sediment disturbances into climate-resilient restoration planning for European marginal seas and provides a transferable approach for advancing restoration across other marginal seas globally.