A Multifaceted Approach to Assessing Climate Change Impacts on Mediterranean EcosystemsExtreme Events

Steeve Comeau^{1, 2}, Jeremy Carlot², Chloé Carbonne³, Frédéric Gazeau^{1, 2}, Melina Sinner^{1, 2}, Samir Alliouane^{1, 2}, Jean-Pierre Gattuso^{1, 2}, Nuria Teixido⁴

¹CNRS, France - ²Sorbonne Université, France - ³Bermudian Institute of Ocean Sciences, Bermuda - ⁴Stazione Zoologica Anton Dohrn, Italy

The Mediterranean Sea is experiencing significant ecological shifts due to global change, particularly through ocean warming and marine heatwaves. Here, we present the importance of long-term monitoring, field surveys and experimental studies to assess the future of Mediterranean ecosystems. Our long-term monitoring of environmental parameters, collected over 30 years in Villefranche-sur-Mer, France, reveal substantial warming of the Mediterranean Sea, alongside an increased frequency and duration of marine heatwaves, and a notable decrease in pH. These changes are likely to influence the resilience and recovery of marine species in response to these stressors. We then assessed the relationship between environmental changes in the Mediterranean Sea and the health of resident benthic communities, specifically focusing on trait groups identified as vulnerable to mass mortality events. Our results indicate significant alterations in ecological traits among benthic species, underscoring the cascading effects of prolonged thermal stress and highlighting 29 functional entities at risk of extreme mortality. Furthermore, we explored with experimental studies how marine heatwaves and warming could affect shallow and mesophotic Mediterranean corals. Our results complement the understanding of the ecological transformations occurring in the Mediterranean Sea and emphasize the importance of coupling long-term data, field survey and experimental work for predicting the future of marine ecosystems in a changing climate.