FN Archimer Export Format PT J TI Unveiling microbiome changes in Mediterranean octocorals during the 2022 marine heatwaves: quantifying key bacterial symbionts and potential pathogens BT AF Prioux, Camille Tignat‑Perrier, Romie GERVAIS, Ophelie Estaque, Tristan SCHULL, Quentin Reynaud, Stéphanie Béraud, Eric Mérigot, Bastien Beauvieux, Anaïs Marcus, Maria-Isabelle Richaume, Justine Bianchimani, Olivier Cheminée, Adrien Allemand, Denis Ferrier‑Pagès, Christine AS 1:1,2,3;2:2,3;3:2,3;4:4;5:5;6:3;7:3;8:6;9:6;10:3;11:4;12:4;13:4;14:3;15:3; FF 1:;2:;3:;4:;5:PDG-RBE-MARBEC-LHM;6:;7:;8:;9:;10:;11:;12:;13:;14:;15:; C1 Collège Doctoral, Sorbonne Université, Paris, France Unité de Recherche sur la Biologie des Coraux Précieux CSM - CHANEL, Centre Scientifique de Monaco, 8 Quai Antoine 1er, Monaco, MC-98000 Monaco, Principality of Monaco Centre Scientifique de Monaco, 8 Quai Antoine 1er, Monaco, MC 98000, Principality of Monaco Septentrion Environnement, Campus Nature Provence, Marseille, 13008, France MARBEC, Univ. Montpellier, CNRS, IFREMER, IRD, Sète, France MARBEC, Univ. Montpellier, CNRS, IFREMER, IRD, Sète, France C2 UNIV SORBONNE, FRANCE CHANEL, MONACO CENTRE SCIENT MONACO, MONACO SEPTENTRION ENVIRONNEMENT, FRANCE IFREMER, FRANCE UNIV MONTPELLIER, FRANCE SI SETE SE PDG-RBE-MARBEC-LHM UM MARBEC IN WOS Ifremer UMR WOS Cotutelle UMR DOAJ copubli-france copubli-univ-france copubli-int-hors-europe IF 15.5 TC 2 UR https://archimer.ifremer.fr/doc/00865/97648/106541.pdf https://archimer.ifremer.fr/doc/00865/97648/106542.docx https://archimer.ifremer.fr/doc/00865/97648/106543.xlsx https://archimer.ifremer.fr/doc/00865/97648/106544.fasta https://archimer.ifremer.fr/doc/00865/97648/106545.fas https://archimer.ifremer.fr/doc/00865/97648/106546.fas LA English DT Article DE ;Corallium rubrum;Paramuricea clavata;Marine heatwaves;Climate change;Bacterial communities;Holobiont;Endozoicomonas;Spirochaetaceae;Gene expression;16S rRNA gene sequencing;qPCR AB Background Climate change has accelerated the occurrence and severity of heatwaves in the Mediterranean Sea and poses a significant threat to the octocoral species that form the foundation of marine animal forests (MAFs). As coral health intricately relies on the symbiotic relationships established between corals and microbial communities, our goal was to gain a deeper understanding of the role of bacteria in the observed tissue loss of key octocoral species following the unprecedented heatwaves in 2022. Results Using amplicon sequencing and taxon-specific qPCR analyses, we unexpectedly found that the absolute abundance of the major bacterial symbionts, Spirochaetaceae (C. rubrum) and Endozoicomonas (P. clavata), remained, in most cases, unchanged between colonies with 0% and 90% tissue loss. These results suggest that the impairment of coral health was not due to the loss of the main bacterial symbionts. However, we observed a significant increase in the total abundance of bacterial opportunists, including putative pathogens such as Vibrio, which was not evident when only their relative abundance was considered. In addition, there was no clear relation between bacterial symbiont loss and the intensity of thermal stress, suggesting that factors other than temperature may have influenced the differential response of octocoral microbiomes at different sampling sites. Conclusions Our results indicate that tissue loss in octocorals is not directly caused by the decline of the main bacterial symbionts but by the proliferation of opportunistic and pathogenic bacteria. Our findings thus underscore the significance of considering both relative and absolute quantification approaches when evaluating the impact of stressors on coral microbiome as the relative quantification does not accurately depict the actual changes in the microbiome. Consequently, this research enhances our comprehension of the intricate interplay between host organisms, their microbiomes, and environmental stressors, while offering valuable insights into the ecological implications of heatwaves on marine animal forests. PY 2023 PD DEC SO Microbiome SN 2049-2618 PU BioMed Central VL 11 IS 1 UT 001114357100001 DI 10.1186/s40168-023-01711-x ID 97648 ER EF