The Great Barrier Reef, the world’s largest coral reef system, is going through a tough time right now. Thanks to man-made climate change, and in part a particularly strong El Niño event, it is undergoing a bleaching event; the coral has become “stressed” and is shedding off its helpful photosynthetic algae, losing its beautiful color as a result. Unfortunately, a new study in the journal Frontiers in Microbiology has some more bad news: It also appears to be severely infected with a herpes-like virus.
Viruses have been found within coral colonies before, either taking advantage of the animal without negatively affecting it, or parasitically, although much about their role in these ecosystems remains unknown. With the Great Barrier Reef set to suffer irreversible damage by 2030 if current warming trends continue, assessing any negative impact viruses have on coral reefs is of paramount importance.
The research team examined samples of the coral Acropora aspera in both its natural habitat and in the laboratory, putting it through various stresses including high temperatures, intense UV light exposure, and simulations of heavy rainfall – all factors known to stress corals out and cause them to ultimately bleach.
Upon bleaching, the corals were found to contain high loads of virus-like particles (VLPs), non-infectious remnants of a viral infection. By looking at the shapes and sizes of these nanometer-sized particles, the team concluded that most of them resembled viruses belonging to several known families, including the herpesvirus, retrovirus and megavirus groups.
The herpes-like VLPs were particularly abundant. They appeared to be similar in size and shape to the herpes virus, but shared very little in common with its genome.
Bleached coral. Ethan Daniels/Shutterstock
As this outbreak seemed to occur during the bleaching event, this suggests that harsh environmental conditions make the coral more vulnerable to infection. In fact, the amount of VLPs found within the coral just three days after bleaching began was two to four times higher than has ever been recorded in corals.
“This is bad news,” said Rebecca Vega-Thurber, an assistant professor of microbiology at Oregon State University’s College of Science and corresponding author of the study, in a statement. “This bleaching event occurred in a very short period on a pristine reef. It may recover, but incidents like this are now happening more widely all around the world.”
None of the viruses could be definitively identified, meaning that they could be new species. Without knowing the exact role they play in coral reefs, the researchers cannot be certain as to how harmful these viruses may be, although they suspect that they could prove dangerous in particularly high concentrations.
The National Oceanic and Atmospheric Administration last year announced that, due to record sea temperatures, the world is in the throes of the third global coral bleaching event, with enormous swathes of coral reefs within the Pacific and Indian oceans severely affected. The fact that this may also be responsible for this newfound viral outbreak is simply a case of adding insult to injury.