Shifts in the coral microbiome in response to 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.
• Format: Text
• Language: English
• Published: American Society for Microbiology 2023
• Subjects: Microbial Ecology; Ocean acidification
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10686059/; http://www.ncbi.nlm.nih.gov/pubmed/37916820; 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. IMPORTANCE: Marine hypoxia is a threat for corals but has remained understudied in tropical regions where coral reefs are abundant. Though microbial symbioses can alleviate the effects of ecological stress, we do not yet understand the taxonomic or functional response of the coral microbiome to hypoxia. In this study, we experimentally lowered oxygen levels around Siderastrea ...