Shifts in the coral microbiome in response to $\textit{in situ}$ experimental deoxygenation

• Published in: Applied and Environmental Microbiology
• Main Authors: Howard, Rachel D., Schul, Monica D., Rodriguez Bravo, Lucia M., Altieri, Andrew H., Meyer, Julie L.
• Other Authors: Red Sea Research Center (RSRC), Department of Soil, Water, and Ecosystem Sciences, University of Florida, Gainesville, Florida, USA, Smithsonian Tropical Research Institute, Balboa, Ancon, Panama, Department of Environmental Engineering Sciences, University of Florida, Gainesville, Florida, USA
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: American Society for Microbiology 2023
• Subjects: Ocean acidification
• Online Access: http://hdl.handle.net/10754/695395; https://doi.org/10.1128/aem.00577-23

Global climate change impacts marine ecosystems through rising surface temperatures, ocean acidification, and deoxygenation. While the response of the coral holobiont to the first two effects has been relatively well studied, less is known about the response of the coral microbiome to deoxygenation. In this study, we investigated the response of the microbiome to hypoxia in two coral species that differ in their tolerance to hypoxia. We conducted in situ oxygen manipulations on a coral reef in Bahía Almirante on the Caribbean coast of Panama, which has previously experienced documented episodes of hypoxia. Naïve coral colonies (previously unexposed to hypoxia) of Siderastrea siderea and Agaricia lamarcki were transplanted to a reef and either enclosed in chambers that created hypoxic conditions or left at ambient oxygen levels. We collected samples of surface mucus and tissue after 48 hours of exposure and characterized the microbiome by sequencing 16S rRNA genes. We found that the microbiomes of the two coral species were distinct from one another and remained so after exhibiting similar shifts in microbiome composition in response to hypoxia. There was an increase in both abundance and number of taxa of anaerobic microbes after exposure to hypoxia. Some of these taxa may play beneficial roles in the coral holobiont by detoxifying the surrounding environment during hypoxic stress or may represent opportunists exploiting host stress. This work describes the first characterization of the coral microbiome under hypoxia and is an initial step toward identifying potential beneficial bacteria for corals facing this environmental stressor. We thank the team at the Smithsonian Tropical Research Institute in Bocas del Toro, Panama, for their assistance in field monitoring and work. This research was supported by the University of Florida start-up funds to A.H.A. and J.L.M. and NSF grant OCE-2048914 to A.H.A. and J.L.M.