Introduction
The Mediterranean Sea is suffering from multiple pressures affecting severely its biodiversity. The region is warming faster than any other sea, causing marine heat waves and ecosystem degradation (Klaoudatos et al., 2024). Phenomena such as ‘tropicalisation’ and ‘meridionalisation ’ are altering the distribution of species, benefiting warm species and displacing native ones. Corals and gorgonians forests are suffering from bleaching and mortality (Ghanem et al., 2021; Kersting et al., 2023) . In Spain, the Plan Complementario de I+D+I en Ciencias Marinas ThinkInAzul (Government of Spain, 2012) has been promoted and one of its objectives is the monitoring of the marine environment. Fish monitoring is crucial, and methods such as the Underwater Visual Census (UVC) have been improved (Azzurro et al., 2022), but it is necessary to standardize the use of sustainable techniques to assess the health of the marine ecosystem.
Materials and methods
A protocol for monitoring impacts of climate change was standardize d by Izquierdo-Muñoz , et al. (2024) and has been implemented for 2-years monitoring of benthic biocenosis and singular species in 4 stations (Oropesa, Pobla de Farnals , Albufera and Calp) along the coast of the Valencian Community, Western Mediterranean Sea . The monitoring protocol was established by conducting Underwater Visual Census (UVC) at rocky bottom locations, coupled with sensible sessile species monitoring (e.g., hard and soft corals) covering a 250 m2 of sampled area in each census under the criteria of presence of the species selected of interest by ThinkInAzul .
Results
A total of 4887 specimens were sighted in the UVC surveys . Differences in the fish composition of the rocky bottom communities show significant differences in relation to season of the year.
Environmental deterioration recorded in the 2084 coral colonies observed in the surveys show mostly healthy specimens with little deterioration. Seasonal variations in the colonies examined showed not significant differences for most of the sample areas.
Discussion and conclusion
The protocol for monitoring impacts of climate change has been applied for a period of 2-years to establish a baseline for comparison in future surveys . The results show indicators of resilience so far to the impacts of marine warming as observed in the low levels of coral bleaching and the dominance of Coris julis over Thalassoma pavo. A shift in proportions between the two species is expected, reducing the abundance of C. julis and increasing T. pavo, linked to the increase in temperature (Azzurro et al., 2022). F uture surveys will provide an early warning system thanks this bioindicators that will allow the detection of climate change trends and its adaptation to other areas of the Mediterranean, with variation and criteria and community species . It is therefore essential to continue the challenges of ThinkInAzul to understand the trends of change in the Mediterranean Sea.
Acknowledgements
This study forms part of the ThinkInAzul programme and was supported by MICIU with funding from European Union NextGenerationEU (PRTR-C17.I1) and by Generalitat Valenciana (GVA-THINKINAZUL/2021/033; Principal Investigator: J. Tena-Medialdea, IMEDMAR-UCV).
We are grateful to Azul Marino Foundation to the support in the fieldworks in Oropesa (Castelló, Spain).
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