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

• Published in: Marine environmental research 2025-01, Vol.203, p.106822, Article 106822
• Main Authors: Sarda, Julia, Gori, Andrea, Doñate-Ordóñez, Ruth, Viladrich, Núria, Costantini, Federica, Garrabou, Joaquim, Linares, Cristina
• Format: Article
• Language: English
• Subjects: adults; Animals; Anthozoa - physiology; Climate Change; Coralligenous; demography; Eunicella; Extreme Heat; Mass mortalities; Mediterranean Sea; Octocorals; Reproduction; species; Sublethal effects; Symbiosis; viability
• ISSN: 0141-1136; 1879-0291; 1879-0291
• DOI: 10.1016/j.marenvres.2024.106822

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. [Display omitted] •The conservation status of Eunicella singularis has deteriorated in the recent years.•Marine heatwaves are affecting the demography and reproduction of E. singularis.•The percentage of non-reproducing colonies has severely increased in the recent years.•Females' reproduction is being more affected than in males.•The photosymbiotic unicellular dinoflagellate Philozoon sp. (Symbiodiniaceae) was identified in the gorgonian tissues.