An NCCOS- and RESTORE-funded study characterized the microbiomes (a collection of microbes) of four octocoral species, i.e. soft corals and sea fans, from low-light (mesophotic) to deep-sea habitats in the northern Gulf of Mexico and found that each octocoral species microbiome was unique. NCCOS scientists discovered that an average coral colony has at least 40 to 70 types of bacteria and microeukaryotes (a type of plankton) living on and in it. Of these microbes, only 9 were abundant and common while the rest were rare. This type of information will be useful in developing restoration plans associated with the Deepwater Horizon Spill.
For most coral species, the full extent of microbiome variability is unknown across their ranges , especially for corals living in deep waters which span greater ranges. The project sampled two mesophotic coral species (Muricea pendula and Swiftia exserta) and two deep-sea coral species (Callogorgia delta and Paramuricea biscaya) with collection depths ranging from 53 to 2224 meters. Coral-associated microbiomes varied greatly between colonies and localities. Depth and geographic location significantly affected diversity, microbial community composition, and the relative abundance of individual microbes. Depth was the strongest environmental factor determining microbiome structure within species. Differences in host genetics, bottom temperature, and surface primary productivity could explain a large part of the microbiome variation associated with depth and geographic location.
Altogether, this work demonstrates that the microbiomes of corals in deep waters vary substantially across their ranges in accordance with depth and other environmental conditions. It reveals that the influence of depth on the ecology of mesophotic and deep-sea corals extends to their microbiomes, which may have functional consequences. This work identifies the distributions of coral-associated microbes, which can help inform restoration plans in the Gulf of Mexico for benthic habitats impacted by the Deepwater Horizon oil spill. For example, a restoration plan could use this information to avoid inadvertently transmitting parasites to new sites through transplants or avoid rearing infected and non-infected corals together in aquaria.
This study is the result of projects funded by NCCOS and the RESTORE program.