Population collapse of habitat-forming species in the Mediterranean: a long-term study of gorgonian populations affected by recurrent marine heatwaves
10 pages, 4 figures, supplemental material https://royalsocietypublishing.org/doi/suppl/10.1098/rspb.2021.2384.-- Data accessibility: All data and code supporting the results are available from the Dryad Digital Repository: https://doi.org/10.5061/dryad.18931zczk ; Understanding the resilience of temperate reefs to climate change requires exploring the recovery capacity of their habitat-forming species from recurrent marine heatwaves (MHWs). Here, we show that, in a Mediterranean highly enforced marine protected area established more than 40 years ago, habitat-forming octocoral populations that were first affected by a severe MHW in 2003 have not recovered after 15 years. Contrarily, they have followed collapse trajectories that have brought them to the brink of local ecological extinction. Since 2003, impacted populations of the red gorgonian Paramuricea clavata (Risso, 1826) and the red coral Corallium rubrum (Linnaeus, 1758) have followed different trends in terms of size structure, but a similar progressive reduction in density and biomass. Concurrently, recurrent MHWs were observed in the area during the 2003–2018 study period, which may have hindered populations recovery. The studied octocorals play a unique habitat-forming role in the coralligenous assemblages (i.e. reefs endemic to the Mediterranean Sea home to approximately 10% of its species). Therefore, our results underpin the great risk that recurrent MHWs pose for the long-term integrity and functioning of these emblematic temperate reefs ; We acknowledge the 'Severo Ochoa Centre of Excellence' (CEX2019–000928-S) funding, the MCIU/AEI/FEDER [HEATMED; RTI2018-095346-B-I00], Interreg-Med Programme (5216 | 5MED18_3.2_M23_007 and 1MED15_3.2_M2_337), Foundation Prince Albert II Monaco [MIMOSA], the TOTAL-Foundation [Perfect] and the European Union's Horizon 2020 research and innovation programme (grant nos. 689518 and SEP-210597628). D.G.-G. is supported by a FPU15/05457 grant. C.L. acknowledges the support of ICREA. J.B.L is supported by the strategic Funding [UIDB/04423/2020 and UIDP/04423/2020]. N.T. received funding by the French National Research Agency-Make Our Planet Great Again [4Oceans-MOPGA and ANR-17-MPGA-0001]. D.K.K. is supported by a IJCI-2017-31457. D.G.-G., C.L., J.B.L., E.C., P.L.-S., D.K.K. and J.G. are part of the Medrecover group [2017 SGR 1521] ; Peer reviewed
