ACCLIMATION CAPACITY OF A CORAL-ALGAL SYMBIOTIC PARTNERSHIP TO LONG-TERM WARMING AND ACIDIFICATION
Elucidating the responses of symbiotic partners to environmental stressors is becoming increasingly important as climate change disrupts biotic interactions worldwide. We exposed the Caribbean coral Siderastrea siderea and its Clade C symbiont to temperature and pCO2 treatments for 95 days and quantified the transcriptomic responses of each partner using RNAseq. Both elevated temperature and pCO2 elicited strong but divergent responses of the host's transcriptome. High temperatures disrupted molecular homeostasis and substantially reduced calcification rates. Conversely, elevated pCO2 enhanced host transcription of genes associated with respiration and hydrogen ion transport, with only minimal effects on calcification rates—underscoring the role of proton transport in calcification maintenance under elevated pCO2, while also suggesting costs associated with this acclimation. Contrary to the host, the symbiont's transcriptome exhibited little change in response to elevated pCO2. Instead, population-specific transcriptomic responses were observed across fore-reef and near-shore environments—consistent with observed differences in symbiont photosynthetic efficiency across these two reefs. We conclude that host transcriptomic plasticity promotes acclimation to ocean acidification, but not necessarily warming. Given the host's strong transcriptomic responses to acidification and warming, coupled with the symbiont's lack of response, we hypothesize that hosts actively buffer their symbiont's environment.
Davies, S. W., University of North Carolina at Chapel Hill, USA, firstname.lastname@example.org
Marchetti, A., University of North Carolina at Chapel Hill, USA, email@example.com
Ries, J., Northeastern University, USA, firstname.lastname@example.org
Castillo, K. D., University of North Carolina at Chapel Hill, USA, email@example.com
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