Mass mortality events linked to marine heatwaves could become the new norm in the Mediterranean Sea
According to the work, that has also involved experts from the Centre d'Estudis Avançat de Blanes (CEAB), the Institut Mediterrani d'Estudis Avançats (IMEDEA), the Instituto Español de Oceanografía (IEO), the Universitat de Barcelona (UB), the Universidad de Alicante (UA), the Universidad de Sevilla (US) and the Museo del Mar de Ceuta, as well as other international centers, populations of some 50 species (including corals, sponges and macroalgae, among others) were affected by these events along thousands of kilometers of Mediterranean coasts, from the Alboran Sea to the Near Eastern coasts.
"Specifically, the impacts of mortalities were observed between the surface and 45 meters' depth, where the recorded marine heat waves were exceptional, affecting more than 90% of the Mediterranean surface and reaching temperatures of more than 26ºC," explains the ICM-CSIC researcher Joaquim Garrabou, one of the authors of the study.
Key species, the most affected
Some of the most affected species are key to maintaining the functioning and biodiversity of the main coastal habitats.
This is the first study to assess the effects of mass mortalities on a Mediterranean scale over five consecutive years.
"Unfortunately, the results of the work show that the Mediterranean Sea is experiencing an acceleration of ecological impacts associated with climate change, posing an unprecedented threat to the health and functioning of its ecosystems," regret Cristina Linares and Bernat Hereu, from the Faculty of Biology and the Biodiversity Research Institute (IRBio) of the UB.
From the exception to the norm
The climate crisis is severely affecting marine ecosystems around the world and the Mediterranean is no exception.
"Given this scenario, it is essential to know the relationship between the different biological responses of marine biodiversity and different levels of heat exposure," points out the US professor Free Espinosa. For their part, David Díaz and Emma Cebrián, researchers at the IEO and the CEAB, respectively, explain that "the high variability of observed responses among species and populations at very different spatial and temporal scales has undermined our ability to explore this relationship."
Now, thanks to the temporal and spatial resolution addressed, it has been possible to demonstrate that there is a significant positive relationship between the duration of heat waves and the incidence of mortality events.
"Mass mortality events in the Mediterranean are equivalent to the bleaching events also observed consecutively in the Great Barrier Reef, suggesting that these episodes are already the norm rather than the exception," highlights the UA professor Alfonso Ramos.
For all these reasons, the authors urge to strengthen coordination and cooperation at regional, national and international levels, as has been done in this work, in order to reach more effective management decisions to cope with the ongoing climate emergency.
Relentless marine heatwave in the Mediterranean.— Scott Duncan (@ScottDuncanWX) July 25, 2022
Record-breaking heat in Europe since the start of May has helped build an immense marine heatwave. Some places hitting more than 5°C warmer than average.
Prolonged & intense marine heatwaves are devastating for marine ecosystems. pic.twitter.com/AiBS9Pnlem
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