Population collapse of habitat-forming species in the Mediterranean: a long-term study of gorgonian populations affected by recurrent marine heatwaves

D. Gómez-Gras , C. Linares , A. López-Sanz , R. Amate , J. Ledoux , N. Bensoussan (1) , P. Drap (2) , O. Bianchimani , C. Marschal (3) , O. Torrents (4) , F. Zuberer (5) , E. Cebrian (6, 7, 8) , N. Teixidó (9) , M. Zabala (10) , S. Kipson , D. Kersting , I. Montero-Serra (11) , M. Pagès-Escolà , A. Medrano , M. Frleta-Valić , D. Dimarchopoulou , P. López-Sendino , J. Garrabou

1 IPSO FACTO [Marseille]
2 LIS - Laboratoire d'Informatique et des Systèmes (LIS) (Marseille, Toulon)
3 IMBE - Institut méditerranéen de biodiversité et d'écologie marine et continentale
4 DIMAR - Diversité, évolution et écologie fonctionnelle marine
5 AMU - Aix Marseille Université
6 CEAB - Centre d'Estudis Avançats de Blanes
7 UdG - Universitat de Girona
8 Institute of Aquatic Ecology
9 LOV - Laboratoire d'océanographie de Villefranche
10 IMB-CNM - Instituto de Microelectrònica de Barcelona
11 UAB - Universitat Autònoma de Barcelona = Autonomous University of Barcelona = Universidad Autónoma de Barcelona

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.

Domaines: Sciences de l'environnement

D. Gómez-Gras, C. Linares, A. López-Sanz, R. Amate, J. Ledoux, et al.. Population collapse of habitat-forming species in the Mediterranean: a long-term study of gorgonian populations affected by recurrent marine heatwaves. Proceedings of the Royal Society B: Biological Sciences, 2021, 288 (1965), pp.20212384. ⟨10.1098/rspb.2021.2384⟩. ⟨hal-03954499⟩