The deep vault: a temporary refuge for temperate gorgonian forests facing marine heat waves

9 pages, 4 figures, 1 table

Climate change poses a significant threat to coastal areas, marked by the increasing intensity and frequency of marine heat waves observed in various ecosystems around the world. Over the last 25 years, a vast number of Mediterranean populations of the red gorgonian Paramuricea clavata have been impacted by marine heatwaves. The last mass mortality occurred during the summer of 2022 in the Western Mediterranean Sea, affecting mostly shallow populations (down to 30 m depth). Here we provide an assessment of the health status of mesophotic P. clavata populations down to 90 m depth to investigate a depth refuge hypothesis. Results show that the impact of marine heat waves decreases with depth, with a significant drop in mortality below 40 m depth. These observations support the hypothesis of a depth refuge from marine heat waves that may allow, at least temporarily, the maintenance of P. clavata in the Western Mediterranean Sea. The present study strongly advocates for further investigations and monitoring of the mesophotic zone to chart potential areas that could serve as deep refuge for gorgonians

L. Bramanti was funded by “BNP PARIBAS climate change and biodiversity initiative” through the DEEPLIFE project; E. Manea was funded by the Marie Curie Actions through the project RESTORE (project number 101062275); B. Giordano was funded by the Doctorate School of the University of Cagliari; T. Estaque, J. Richaume and O. Bianchimani were funded by OFB (Office français de la Biodiversité); B. Mérigot and Q. Schull were supported by the LabEx CeMEB for the DEEP HEART project; J. Garrabou acknowledges the support of the Severo Ochoa Centre of Excellence, Grant/Award Number: CEX2019-000928-S, European Union Horizon 2020 research and innovation programme (Futuremares SEP-210597628) and TED2021-131622B-I00 CORFUN project

Peer reviewed