Cold-water Coral Microbiome and Environmental Microbial Communities in a Remote NE Atlantic Submarine Canyon Setting: Microbial Diversity, Coral Health and Prospects

In the Porcupine Bank Canyon, Lophelia pertusa and Madrepora oculata are the main framework-forming corals producing three dimensional structures which provide a home for a range of benthic fauna and microbial communities. To understand the roles and functions that microbes perform in coral health in the Porcupine Bank Canyon, three groups of samples (corals, sediment and water) were collected between 600–800 m depth. DNA was extracted from these samples and metabarcoding was performed on the V3-V4 region of the 16S RNA gene using Illumina technology. The coral microbiome showed greater microbial diversity than both the surrounding sediment and water communities. The genera Pseudomonas , Pseudoalteramonas and Photobacterium were the bacterial communities conserved at 100% coverage of coral samples whereas at the order-level classification Clostridiales, Bacteroidales, Flavobacteriales, Rhodobacterales and Rickettsiales were in high abundance in all the coral samples. A disproportionate distribution of probiotic and pathogenic bacterial groups at the different levels of classification was observed on the corals. Corals do not appear, at present, to be stressed by climate induced changing environmental conditions in the upper Porcupine Bank Canyon. Overall, the corals in the Porcupine Bank Canyon are in a healthy state despite the detection of pathogenic bacterial groups. However, the current trend of climate change and subsequent deep-sea warming could shift the bacterial composition towards a more dominant pathogenic bacterial community, with serious implications for coral health and stability of this important ecosystem.