Combined responses of primary coral polyps and their algal endosymbionts to decreasing seawater pH

With coral reefs declining globally, resilience of these ecosystems hinges
on successful coral recruitment. However, knowledge of the acclimatory
and/or adaptive potential in response to environmental challenges such as
ocean acidification (OA) in earliest life stages is limited. Our
combination of physiological measurements, microscopy, computed tomography
techniques and gene expression analysis allowed us to thoroughly elucidate
the mechanisms underlying the response of early life stages of corals,
together with their algal partners, to the projected decline in oceanic
pH. We observed extensive physiological, morphological and transcriptional
changes in surviving recruits, and the transition to a
less-skeleton/more-tissue phenotype. We found that decreased pH conditions
stimulate photosynthesis and endosymbiont growth, and gene expression
potentially linked to photosynthates translocation. Our unique holistic
study discloses the previously unseen intricate net of interacting
mechanisms that regulate the performance of these organisms in response to
OA.