pH up-regulation as a potential mechanism for the cold-water coral Lophelia pertusa to sustain growth in aragonite undersaturated conditions

[摘要] Cold-water corals are important habitat formers in deep-water ecosystems andat high latitudes. Ocean acidification and the resulting change in aragonitesaturation are expected to affect these habitats and impact coral growth.Counter to expectations, the deep water coral Lophelia pertusa hasbeen found to be able to sustain growth even in undersaturated conditions.However, it is important to know whether such undersaturation modifies theskeleton and thus its ecosystem functioning. Here we used SynchrotronX-Ray Tomography and Raman spectroscopy to examine changes in skeletonmorphology and fibre orientation. We combined the morphological assessmentwith boron isotope analysis to determine if changes in growth are related tochanges in control of calcification pH. We compared the isotopic compositionand structure formed in their natural environment to material grown inculture at lower pH conditions. Skeletal morphology is highly variable butshows no distinctive differences between natural and low pH conditions. Ramaninvestigations found no difference in macromorphological skeletal arrangementof early mineralization zones and secondary thickening between thetreatments. The δ¹¹B analyses show that L. pertusaup-regulates the internal calcifying fluid pH (pH_cf) duringcalcification compared to ambient seawater pH and maintains a similar elevatedpH_cf at increased pCO₂ conditions. We suggest that as longas the energy is available to sustain the up-regulation, i.e. individuals arewell fed, there is no detrimental effect to the skeletal morphology.

[学科分类] 地球化学与岩石