Understanding the influence of swarming timing on the dispersal of Ostrea edulis larvae in the Northern Adriatic Sea

Abstract

Background Ostrea edulis, the European Oyster, is a key habitat engineering species, considered “functionally extinct” in much of its native range, however the presence of population patches, large enough to allow the recruitment of juveniles, is likely, at least in the Northern Adriatic Sea. In order to decide which areas to protect or enhance with substratum suitable for settlement, it is necessary to understand larval dispersal dynamics. The main research question was to understand how the settlement areas depends on the timing of swarming and on larvae emission location. Methods Larval dispersal modelling tools already exist, and for the purpose of this study the use of an open-source phyton model code ‘Opendrift’, parametrised for O. edulis larvae with specific parameters related to growth and speed of vertical movement, based on existing literature data. Necessary forcing functions (currents, temperature) were taken from Copernicus, and gridded bathymetry data was downloaded from GEBCO repository. Results The results of this preliminary model-based study showed that the settling areas depend on the timing of the emission periods, given that different emissions can lead to different time spent as plankton maturing to settlement, therefore potentially reaching further. Initial seeding location can also matter, due to differences in currents that could be encountered. Conclusions Some experimental validation should follow this modelling approach, including genetic analyses to verify sources, this setup using an open data and an open access existing modelling framework to predict larval settlement is promising in enabling the upscaling and application for restoration and conservation purposes in other areas.