Periodic Reporting for period 1 - RESTORE (Targeting a science-based approach to REd coral reSTORation in a climate change scEnario)
Reporting period: 2022-12-01 to 2024-11-30
Corals are priority targets of restoration efforts because they are ecosystem engineers that support high biodiversity and provide many ecosystem services. RESTORE dealt with the need to build the knowledge needed to advance science-based restoration of Mediterranean octocorals, particularly Corallium rubrum, the precious red coral, and Eunicella singularis, the white gorgonian. Both are species of great ecological value and priority for conservation under European legislations due to their vulnerability to anthropogenic impacts. RESTORE aimed at develop innovative nature-based restoration approaches harnessing ecological processes, thereby underpinning octocoral recruitment success and overcoming the limitations of the existing restoration methods (e.g. coral transplantation). Indeed, these approaches are rarely adapted to the biology of the organism being restored and are not based on the ecological processes fundamental to the reproduction and survival of the species. Nature-based approaches that take advantage of ecological processes (i.e. relying on sexually derived propagules and improved larval settlement to support coral recruitment and growth successes), are more promising for corals’ long-term recovery and for improving their resilience to climate change. RESTORE explored the potential to exploit positive species interactions - i.e. between coral larvae, coralline algae and their associated microbiome, which are recognized as potentially enabling factors to enhance coral larvae recruitment. The knowledge gained paves the path towards the development of low-cost and high-yield nature-based restoration protocols for these species. Mathematical spatial and predictive distribution models were also adopted to inform species conservation and restoration actions taking into account climate change. RESTORE delivered relevant outcomes to support restoration actions under the EU Biodiversity Strategy, Green Deal, and Nature Restoration Law.
In the framework of the RESTORE project, two crustose coralline algae (CCA) species observed to live associated with octocoral juveniles in the area of Banyuls-sur-Mer (France) were identified to be Macroblastum dendrospermum and Lithophyllum stictiforme through barcoding (Sanger) analysis. The 16S rDNA metabarcoding analysis of the bacteria communities associated with the two CCA species showed that the two algal species are characterized by species-specific bacterial assemblages. Despite this specificity, both CCA species predominantly host bacterial taxa that have been observed to characterize the microbial communities of many CCA species and to have a potential role in favouring tropical coral larvae settlement. Through an experimental test in aquaria and control conditions, the two CCA species and their bacteria were tested for their capability of promoting the settlement of larvae of the white gorgonian E. singularis, also after being subjected to climate change effects. Replicates of each CCA species were subjected to three different experimental conditions for two months: 1 - Control conditions. Normal conditions of pH (pHT≈8.1) and temperature (T≈16.1°C) for control CCA samples. Three bare rock fragments were also exposed to the control conditions and used as experimental control samples. 2 - Treatment 1 (T1). Acidified and warming conditions projected in the RCP8.5 scenario foreseen at the end of the 21st century with pH value corresponding to 7.70 and a temperature increase of 2.5°C; 3 - Treatment 2 (T2). same conditions of water acidification and warming followed by the reproduction of a heatwave phenomenon at 26°C foreseen in the area starting from 2050. At the end of the treatment period, part of the algae was sampled to explore potential changes in their bacterial community composition, algae exo-metabolites were sampled for metabolomic analysis, and the water conditions in each aquarium were restored to normal conditions. Octocoral larvae were then equally distributed in the aquaria and checked every day for two months to count the number of settlers.
Extracts of grounded CCA fragments were subsequently used to obtain purified bacterial strains that were identified by means of barcoding analysis of the 16S rDNA gene. Most of the bacterial strains were successfully identified. The capability of each strain to produce biofilm was assessed by crystal violet staining technique, and all bacterial strains were found to be biofilm producers. Biofilms were used in a second octocoral larval settlement test.
The RESTORE project also explored the effect of climate change on the presence and spatial distribution of the red coral C. rubrum in the Western Mediterranean by implementing predictive models of species distribution. Spatial data searching and gathering of coral presence and environmental parameters were carried out by using open-access data portals. The environmental parameters known to influence C. rubrum distribution and presence were selected. Environmental data were found in CMEMS and EMODnet data portals with 200 m spatial resolution. As for temperature, dissolved oxygen, and current velocity, data were also collected for climate change scenarios’ analysis starting from the IPCC scenario SSP5-8.5 predicted for 2100. The data were analyzed, processed, and used to build and test the performances of three species distribution models, GAM, Maxent, and Random Forest.
Extracts of grounded CCA fragments were subsequently used to obtain purified bacterial strains that were identified by means of barcoding analysis of the 16S rDNA gene. Most of the bacterial strains were successfully identified. The capability of each strain to produce biofilm was assessed by crystal violet staining technique, and all bacterial strains were found to be biofilm producers. Biofilms were used in a second octocoral larval settlement test.
The RESTORE project also explored the effect of climate change on the presence and spatial distribution of the red coral C. rubrum in the Western Mediterranean by implementing predictive models of species distribution. Spatial data searching and gathering of coral presence and environmental parameters were carried out by using open-access data portals. The environmental parameters known to influence C. rubrum distribution and presence were selected. Environmental data were found in CMEMS and EMODnet data portals with 200 m spatial resolution. As for temperature, dissolved oxygen, and current velocity, data were also collected for climate change scenarios’ analysis starting from the IPCC scenario SSP5-8.5 predicted for 2100. The data were analyzed, processed, and used to build and test the performances of three species distribution models, GAM, Maxent, and Random Forest.
The experimental results showed higher settlement rates of larvae of E. singularis on the two CCAs compared to control samples, especially on the algae previously subjected to warming and acidification conditions. Thanks to the analyses of the metabolomic profiles of CCAs’ exudates and of the bacterial diversity, it was possible to formulate the hypothesis of the facilitative role of certain exudates and of three bacterial taxa in larval settlement success. The use of bacterial biofilms in the subsequent experimental test showed that larvae settled in the presence of two biofilms, while in the presence of eight bacterial strains, half of the larvae died after about ten days of incubation. At this stage, further research and experimental studies are needed to develop and test restoration protocols based on the project results. Regarding species distribution model outputs, preliminary results showed a general rarefaction of C. rubrum populations presence in the Western Mediterranean Sea and their shift to greater depths by 2100 according to IPCC scenario SSP5-8.5.