Climate crisis drives Mediterranean coral populations to collapse
Marine heat waves are leading to the collapse these populations, reducing in some cases their biomass by 80 to 90%.
28/01/2022 A new study led by researchers from the project Coral Alert reveals hat marine heat waves associated with the climate crisis are leading to the collapse of coral populations in the Mediterranean, reducing their biomass by 80 to 90%. According to the work, Mediterranean coral populations, which are key to the functioning of coral reefs, one of the most emblematic habitats of this sea, may be unable to recover from the recurrent impact of these extreme events during which water temperatures reach very high levels for days or even weeks. This is the first study to assess the long-term resilience of populations of the two most emblematic coral species in the Mediterranean: the red gorgonian (Paramuricea clavata) and the red coral (Corallium rubrum), which provide essential complex habitats for a great diversity of associated fauna. Understanding their resilience to increasingly frequent and intense heat waves is therefore crucial. Mass mortality events Climate crisis is severely affecting marine ecosystems around the world, and the Mediterranean is not an exception. In particular, marine heat waves associated with this crisis are causing mass mortality events in all coastal ecosystems of this basin. Among the most affected species are Mediterranean corals. Although numerous studies have investigated the immediate impacts of marine heat waves on coral species, very little is known about their long-term resilience. The main reason for this is that, as these species are generally very long-lived (> 100 years in some cases) and have slow population dynamics, i.e. organisms with low growth and recruitment rates, long time series (decades) are needed to assess their resilience. To carry out the study, researchers analysed the results obtained in a long-term monitoring of different coral populations that were affected by a large mass mortality event caused by a heat wave in 2003 in the Scandola (Corsica, France) marine protected area. Specifically, data on the state of these populations (density, size structure and biomass) was collected over the following 15 years by researchers from the Medrecover research group, made up of experts from the ICM-CSIC and the UB, among other centres. Unfortunately, the results showed that, far from recovering, all populations analysed have tended to collapse since they were affected by the 2003 heat wave. In fact, after 15 years, these populations can be considered practically extinct from a functional point of view. "We have observed average biomass losses with respect to the initial biomass of around 80% for the red gorgonia populations, and up to 93% in the case of the red coral population studied", explains Daniel Gómez, researcher at the ICM-CSIC and one of the authors of the study. Joaquim Garrabou, also a researcher at the ICM-CSIC and another of the authors of the study, warns that "these data are very worrying for the conservation of these emblematic species, and indicate that the effects of the climate crisis are accelerating, with obvious consequences for underwater landscapes, where the loss of corals is equivalent to the loss of trees in forests". __ Read full press release here. Photo by Joana Colomer - CIB (see record)