Field experimentation started in September 2021 and lasted until October 2023, and included monitoring of the oysters, environmental data collection, spat collectors deployment and collection with analyses in the laboratory of recruitment and associated biodiversity, routine cleaning of grow-out gear. The experimental design was an essential aspect, and collaborations and networking with external parties were necessary activities for planning. The Native Oyster Restoration Alliance (NORA) helped with sourcing oysters, in accordance with restoration principles. The collaboration with marine ecologists at Ca' Foscari - DAIS was very productive, facilitating the field surveys and supporting both the chemical analysis and the characterization of the phytoplanktonic community. The activities carried out in the field supported the modelling work. The data collected were also shared with aquaculture operators and stimulated further research questions.
In terms of the modelling activities that went hand in hand with the field sampling, a bioenergetic model to predict growth of mussels and oysters considering the growth of shell tissue, somatic tissue and gonads was parametrised, with data from the literature and included the fine tuning of a parameter related to feeding capacity of the organism (maximum clearance rate), which was found to have a large variability in the literature. To achieve this goal, growth data from other regional zones were taken from the literature to calibrate this parameter in order to enable the application of the model beyond the study area, linking the maximum clearance rate to the energetic content of the food available in the region.
This model was then coupled with a water chemistry model, to allow the quantification of carbon fluxes associated with processes linked to growth and energy. This was not explicitly foreseen in the Annex but was considered to be a necessary piece towards the SO4 and quantification of ecosystem functioning. This was done both for the mussels and the oysters. Simulations for mussels were then done for the whole Mediterranean basin (having focused the work on the Mediterranean mussel, Mytilus galloprovincialis), in areas where aquaculture is known to take place. This work was published in AMBIO (Bertolini et al, 2023 – see dissemination paragraph). The oysters module simulations were done to simulate reef restoration with one cohort of adults for 7 macro-sites across the whole latitudinal range of the species (from Turkey to Norway, three in the Mediterranean, four in the Atlantic) and to provide some tools for restoration and accounting of ecosystem services beyond our case study area and understand the influence of environmental variables. Furthermore, having developed the models for both species, it would be possible to use them in tandem to quantify carbon in the case of the coupled cultured systems. The work on carbon fluxes was improved thanks to discussions with international groups of researchers working on carbon balances associated with shell processes (forming, dissolving), specifically improving the understanding of the current scientific debates in which calcification is at times considered a sink and other times considered a source, and in this work calcification was considered as a net source of CO2 in the atmosphere due to its effects on water carbonate. This work was presented at two conferences and is currently being prepared for submission to a peer-reviewed journal. Simulations made use of open access satellite data, applying the learning from the courses taken in WP2 and maximising knowledge transfer from the research group.
Larval dispersal was also investigated using modelling. This model was primarily applied to the northern Adriatic Sea, where reproductive adult oysters were assumed to be present on wrecks (as per SCUBA divers personal communications) and a specific sampling campaign should be developed in the future to validate the results, but some observations and personal discussions with stakeholders point to the presence of oyster spat in areas identified as potential settling zones with the model. The results were presented in a paper submitted to Open Research Europe, which is currently undergoing peer-review. In the Venice lagoon, difficulties on applying the model arose from the impossibility of obtaining current measurements from satellite (not available); therefore, the model was run with an old current model available from a previous project for the year 2019. Settlement experiments were conducted to investigate effects of timing and depth, which were considered two essential factors according also to the literature review conducted at the very beginning of the project. The results highlighted the preference for deeper areas for Ostrea edulis compared to the non-native Crassostrea gigas which tended to settle in the shallower collectors, giving rise to novel hypothesis regarding niche segregation of these two species. Biodiversity associated with culturing gear and specifically with the collectors has also been monitored and investigated to understand potential associations and interferences such as competition.
