London: A new disease has emerged that alters the community of microbes found on corals, according to a study which suggests that tracking these changes may help in monitoring health across reefs. Researchers, including those from the University of Derby in the UK, surveyed coral reefs across the Indian and Pacific Oceans between 2011 and 2018 for signs of this new grey-patch disease, and found that it is currently restricted to Micronesia — a sub region in the western Pacific Ocean consisting of thousands of small islands.
The study, published in the journal Microbiome, noted that the disease is characterised by the growth of a thin grey layer of a type of bacteria called cyanobacteria. The bacteria form a mat, or a biofilm, that over grows the live coral tissue, the study said. The researchers tagged 12 Porites — a large species of coral — at Luminao reef in Guam — a US island territory in Micronesia.
They found that the disease had affected 18 different coral species, and was seen in nearly 22 per cent of the surveyed colonies. According to the researchers, the disease was slow to progress, and some coral tissue was able to grow back over the bacterial mat.
“Upon analysis of the coral samples, multiple microorganisms appeared to be involved in degrading the corals’ defences causing the onset of the disease,” said study lead author Michael Sweet from the University of Derby. “This supports recent findings that suggest we should shift from the one-pathogen-one-disease model, to exploring the importance of multiple pathogens in any given disease,” Sweet added. The researchers said the community of microbes, or the microbiome, living on the corals was significantly altered after the cyanobacterial infection.