Near‐future ocean acidification causes differences in microbial associations within diverse coral reef taxa

• Published in: Environmental Microbiology Reports
• Main Authors: Webster, N. S., Negri, A. P., Flores, F., Humphrey, C., Soo, R., Botté, E. S., Vogel, N., Uthicke, S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2012
• Subjects: Ocean acidification
• Online Access: http://dx.doi.org/10.1111/1758-2229.12006; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2F1758-2229.12006; http://onlinelibrary.wiley.com/wol1/doi/10.1111/1758-2229.12006/fullpdf

Summary Microorganisms form symbiotic partnerships with a diverse range of marine organisms and can be critical to the health and survival of their hosts. Despite the importance of these relationships, the sensitivity of symbiotic microbes to ocean acidification ( OA ) is largely unknown and this needs to be redressed to adequately predict marine ecosystem resilience in a changing climate. We adopted a profiling approach to explore the sensitivity of microbes associated with coral reef biofilms and representatives of three ecologically important calcifying invertebrate phyla [corals, foraminifera and crustose coralline algae ( CCA )] to OA . The experimental design for this study comprised four pHs consistent with current IPCC predictions for the next few centuries ( pH NIST 8.1, 7.9, 7.7, 7.5); these pH / p CO 2 conditions were produced in flow‐through aquaria using CO 2 bubbling. All reduced pH /increased p CO 2 treatments caused clear differences in the microbial communities associated with coral, foraminifera, CCA and reef biofilms over 6 weeks, while no visible signs of host stress were detected over this period. The microbial communities of coral, foraminifera, CCA and biofilms were significantly different between pH 8.1 ( p CO 2 = 464 μatm) and pH 7.9 ( p CO 2 = 822 μatm), a concentration likely to be exceeded by the end of the present century. This trend continued at lower pHs /higher p CO 2 . 16 S rRNA gene sequencing revealed variable and species‐specific changes in the microbial communities with no microbial taxa consistently present or absent from specific pH treatments. The high sensitivity of coral, foraminifera, CCA and biofilm microbes to OA conditions projected to occur by 2100 is a concern for reef ecosystems and highlights the need for urgent research to assess the implications of microbial shifts for host health and coral reef processes.