Introduction
The European native oyster (Ostrea edulis) is a keystone species once abundant across European seas, forming extensive biogenic reefs, but it is currently considered as threatened and/or declining due to overfishing, habitat degradation, pollution, and disease (OSPAR, 2013) .
Conservation and restoration efforts are now essential, not only to conserve the species but also to reinstate the ecosystem services oysters provide, such as enhancing biodiversity, improving water quality, and contributing to coastal resilience (Pogoda et al., 2020).
A critical component of effective restoration is understanding larval dispersal and recruitment, which informs the optimal placement and design of restoration sites and protected areas (Korringa , 1946). This study simulates larval dispersal and settlement potential of O. edulis to support targeted restoration strategies in Northern Ireland’s coastal marine area.
Modelling approach
We applied the OpenDrift particle-tracking framework (opendrift.github.io), using its LarvalFish module to simulate the dispersion of native oyster larvae in three Northern Ireland’s sea loughs: Belfast, Larne and Carlingford . Opendrift benefits from being highly customizable in terms of larval behaviour, agnostic with regard to the underlying hydrodynamic model and from allowing for a cross-domain/cross-model calculation of dispersion. It also allows for backward tracing of the dispersion paths, the introduction of pseudo-random stochastic variability and for a customizable coastline detection behaviour.
A Delft3D-Flow hydrodynamic model with a domain covering from the Larne to Carlingford Lough was used as the main source of time-varying 3-dimensional velocity fields for the Opendrift model.
A dedicated O. edulis larvae dispersion model was developed for the Opendrift platform (OedulisLarvaeDrift ) that implements the current state-of-the-art knowledge on the early life-cycle of the native oysters. In addition to the physical behaviour of neutrally-buoyant particle, the following high-level responses were included to simulate the growth, motility, mortality and settling of the O. edulis larvae:
As the a vailability of suitable settlement substrate is one of the main factors governing recruitment success of oyster populations (Rodriguez-Perez et al. 2021), our dispersal model integrates benthic habitat maps to evaluate the settlement success in the three loughs.
Larval sampling was conducted early in the seedling collection season to calibrate the horizontal distribution of hatched larvae to be used as the initial distribution for particle tracking. A sensitivity analysi s explored how variation in uncertain parameters—such as pediveliger stage duration, swimming speed, and survival rates—affected dispersal and settlement outcomes.
References
OSPAR. (2013). OSPAR Recommendation 2013/4 on furthering the protection and conservation of Ostrea edulis in Region II of the OSPAR maritime area and Ostrea edulis beds in Regions II, III and IV of the OSPAR maritime area.
Pogoda, B., Boudry , P., Bromley, C., Cameron, T.C., Colsoul , B., Donnan, D. et al. (2020a). NORA moving forward: developing an oyster restoration network in Europe to support the Berlin oyster recommendation. Aquatic Conservation: Marine and Freshwater Ecosystems , 30(11), 2031–2037. https://doi.org/10.1002/aqc.3447
Korringa , P. (1946 ) A Revival of Natural Oyster Beds? Nature 158 , 586–587. https://doi.org/10.1038/158586d0
Rodriguez-Perez A, James MA, Sanderson WG (2021) A small step or a giant leap: Accounting for settlement delay and dispersal in restoration planning. PLoS ONE 16(8): e0256369. https://doi.org/10.1371/journal.pone.0256369
Acknowledgments/Funding
Funding for this research was provided by the Department of Agriculture, Environment and Rural Affairs (DAERA) under the Environment Fund 2023–28. Northern Ireland Water financial support made the development of the Delft3D c oastal domain possible.