Exploring the response of a key Mediterranean gorgonian to heat stress across biological and spatial scales

14 pages, 5 figures, 2 tables, supplementary information https://doi.org/10.1038/s41598-022-25565-9.-- Data availability: The datasets used and/or analyzed during the current study available from the corresponding author on reasonable request

Understanding the factors and processes that shape intra-specific sensitivity to heat stress is fundamental to better predicting the vulnerability of benthic species to climate change. Here, we investigate the response of a habitat-forming Mediterranean octocoral, the red gorgonian Paramuricea clavata (Risso, 1826) to thermal stress at multiple biological and geographical scales. Samples from eleven P. clavata populations inhabiting four localities separated by hundreds to more than 1500 km of coast and with contrasting thermal histories were exposed to a critical temperature threshold (25 °C) in a common garden experiment in aquaria. Ten of the 11 populations lacked thermotolerance to the experimental conditions provided (25 days at 25 °C), with 100% or almost 100% colony mortality by the end of the experiment. Furthermore, we found no significant association between local average thermal regimes nor recent thermal history (i.e., local water temperatures in the 3 months prior to the experiment) and population thermotolerance. Overall, our results suggest that local adaptation and/or acclimation to warmer conditions have a limited role in the response of P. clavata to thermal stress. The study also confirms the sensitivity of this species to warm temperatures across its distributional range and questions its adaptive capacity under ocean warming conditions. However, important inter-individual variation in thermotolerance was found within populations, particularly those exposed to the most severe prior marine heatwaves. These observations suggest that P. clavata could harbor adaptive potential to future warming acting on standing genetic variation (i.e., divergent selection) and/or environmentally-induced phenotypic variation (i.e., intra- and/or intergenerational plasticity)

This work was financially supported by the European Union's Horizon 2020 research and innovation programme [grants 689518—MERCES and SEP-210597628—FutureMARES], by MCIU/AEI/FEDER [RTI2018-095346-B-I00; HEATMED] and by the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S). This research has also been funded by the Interreg Med Programme (grants 5216|5MED18_3.2_M23_007 and 1MED15_3.2_M2_337), 85% co-funded by the European Regional Development Fund. D.G-G. was supported by an FPU grant [FPU15/05457]. C.L acknowledges the support by ICREA Academia. G. P., D.P., M.C., E.A. S. and J-B. L. were funded by FCT—Foundation for Science and Technology, through UIDB/04326/2020, UIDP/04326/2020, LA/P/0101/2020, DivRestore/0013/2020. D.G-G, C.L, P.L-S, J-B. L and J.G. are part of the Marine Conservation research group [2017 SGR 1521]. M.C. was supported by a postdoctoral fellowship of project HABMAR (Grant No. MAR-01.04.02-FEAMP-0018) co-financed by the European Maritime and Fisheries Fund of the Operational Program MAR 2020 for Portugal

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