15 January 2019
A coral disease alert system
Published online 6 November 2018
Chemicals that diffuse from coral surfaces into the surrounding seawater could be used as indicators of coral health.
Changes in the chemicals released by microbes present on coral surfaces could be indicative of disease, according to a study conducted in the United Arab Emirates.
Corals are immobile organisms that must be able to quickly adapt to changes in their environment in order to survive. One of the ways they do this is by covering their surface with a mucus layer that harbours a diverse microbial community.
“The chemicals on the coral surface can act as anti-bacterials, to fend off harmful microbes, or they can be chemo-attractive, luring beneficial microbes,” explains marine microbiologist Shady Amin at New York University Abu Dhabi.
Changes in temperature, light or salinity can trigger a change in the chemical composition of the mucus and a shift in the residing microorganisms. This is likely to influence the recruitment of beneficial microorganisms and could increase the corals’ susceptibility to infection.
“The aim of our research is to characterize how corals respond to their environment in order to better predict the mechanisms that lead to coral disease, a major cause of coral population decline worldwide,” says Amin.
Previous research showed dramatic changes in the chemical profile surrounding the surfaces of infected corals. Amin and his team analysed water samples taken at various distances from two different species of coral colonies in the Arabian Gulf. They found that these colonies produce a cloud of molecules that is distinctly different from the surrounding seawater and can be detected up to five centimetres away from their surfaces.
They identified six potential coral disease indicators, which could inform scientists about the health state of corals. Further characterising these chemical signatures could help predict coral disease before it happens, prompting intervention. “Our findings suggest that by identifying candidate biomarkers of coral diseases we can, in theory, develop an early warning system that can be used for monitoring efforts,” Amin says.
Manuel Aranda, a coral reef genomics expert at the Red Sea Research Center of Saudi Arabia’s King Abdullah University of Science and Technology, is excited about the implications of this method for exploring other aspects of coral biology. “By using the techniques described in this study we will be able to gain in-depth knowledge of the chemically mediated communication between corals and their symbiotic microbial communities,” explains Aranda, who was not involved in the study. “This will open a whole new world of things we can look at and provide new insights into the dynamics of coral microbial communities,” he adds.
Amin and colleagues are planning on expanding their work to include other coral species in a wider range of geographic locations.
Ochsenkühn, M. A. et al. Coral metabolite gradients affect microbial community structures and act as a disease cue. Commun. Biol. 1, 184 (2018).