Assessing the Potential of Innovative Clay Designs for Enhancing Oyster Reef Restoration

The restoration of European flat oyster (Ostrea edulis) population is critical for biodiversity and ecosystem services recovery. This study evaluates the potential of innovative clay substrates, developed and patented by Oyster Heaven, as cost-effective and degradable alternatives for large-scale oyster reef restoration. Field trials conducted in an oyster aquaculture site and hatchery experiments under controlled conditions assessed the larvae settlement efficiency, microbial biofilm composition, and environmental influences. Results showed significantly lower larvae recruitment on clay prototypes and spat collectors used as control, in wild conditions, with environmental factors such as temperature and hypoxia playing a key role. In the hatchery, larvae preferred oyster shells (17,174 ± 659 spats/m²) over clay prototypes (2917 ± 111 spats/m²) and spat collectors (1451 ± 160 spats/m²). Microbial analysis revealed a shift towards Cyanobacteria and Woeseia species, with Pseudoalteromonadaceae, a genus previously linked to both stimulating and inhibiting larvae settlement, detected only on clay surfaces. Despite challenges, the clay prototypes demonstrated potential as sustainable substrates for restoration, particularly in managed “spats-on-reefs” strategies. This research highlights the importance of environmental monitoring, microbial interactions, and substrate optimization in enhancing restoration success for O. edulis populations. Further investigations are recommended to refine clay designs and assess their broader applicability under variable environmental conditions.