Recurrent marine heatwaves compromise the reproduction success and long-term viability of shallow populations of the Mediterranean gorgonian Eunicella singularis

12 pages, 9 figures, 2 tables, supplementary data https://doi.org/10.1016/j.marenvres.2024.106822.-- Data availability: Data will be made available on request

Mediterranean gorgonians are being threatened by the impact of recurrent extreme climatic events, such as marine heatwaves (MHWs). The white gorgonian Eunicella singularis was suggested to be the most resistant gorgonian species in the NW Mediterranean, mainly due to the presence of symbiotic algae. However, a substantial shift in the conservation condition of the species has been observed in the recent years. The aim of this study is to evaluate the lethal and sublethal effects of recent MHWs on the populations of E. singularis. Our results show that recurrent MHWs have impacted both the demography and reproduction of the species between 2002 and 2020, driving mortalities up to 36%, an increase in the percentages of non-reproducing adult colonies (11–58%), and a significant decrease in the recruitment rates. Although E. singularis is a highly dynamic species in comparison with other temperate gorgonians, the present study suggests that the persistence of this species may be severely compromised under recurrent MHWs, at least at shallowest depths

This research has been partially supported by the HEATMED project (RTI2018-095346-BI00) funded by MICIU/AEI/10.13039/501100011033, the CORFUN project (TED2021-131622B-I00) funded by MICIU/AEI/10.13039/501100011033 and the European Union NextGenerationEU/PRTR, and the UndResCoral project (PID2022-137539OB-C21) funded by MICIU/AEI/10.13039/501100011033 and by FEDER, UE. JS was supported by an FI Joan Oró 2023 grant (2023 FI-1 00260) from the Ministry of Research and Universities of the "Generalitat de Catalunya" and a PREDOC-UB 2022 grant from the University of Barcelona. CL gratefully acknowledges the financial support by ICREA under the ICREA Academia Program. JG acknowledges the Severo Ochoa Centre of Excellence grant (CEX2019-000928-S) funded by MICIU/AEI/10.13039/501100011033. The authors are part of the Marine Conservation Research Group – MedRecover (2021 SGR01073) from the Generalitat de Catalunya. And AG, NV and FC are part of the COST ACTION Marine Animal Forests of the World (MAF-WORLD, CA20102) supported by COST (European Cooperation in Science and Technology)

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