Warming temperatures and ocean acidification are significant threats to coral reefs, but a new study by Mote Marine Laboratory researchers last month provides something of a silver lining. Researchers found that ocean acidification could actually help slow the progression of a disease that kills corals.
The study was published in June in the Public Library of Science Journal One (PLOS ONE). It explores the effects of ocean acidification, or decreasing pH levels, on the harmful growth of black band disease on hard corals. Black Band is a bacterium that affects more than 40 coral species worldwide.
It can move across a reef, simultaneously killing and consuming healthy coral tissue at a rate of several centimeters a day. Erinn Muller, Ph.D., is the lead author of the report and Manager of Mote’s Coral Health and Disease Research Program. She said black band can kill off several hundred year-old corals in just a matter of weeks given that some coral species like brain and boulder corals only grow at a rate of a few millimeters per year. Muller said researchers went into the study thinking that since ocean acidification is harmful to coral, it would make it more susceptible to black band disease, but that was not the case.
“What we saw really surprised us. It actually reduced the progression rates, albeit only by about 25 percent. So, this disease is still progressing quite rapidly, but it was negatively impacted by low pH,” said Muller.
“So that just gives us insight into the complexity within some of these disease ecologies and how the environment may surprise us in the way that it interact with the pathogenicity of it.”
Muller points out though, that the prevalence of black band disease increases in warmer waters, and since warming ocean temperatures and ocean acidification occur in the natural environment simultaneously, that could lessen the impact of the study’s research findings.
“We have to take this kind of glimmer of hope with a grain of salt because as much as we would love to see reduced virulence of this disease, the way things are changing, it’s probably going to have minimal impact ecologically within our oceans,” said Muller.
Dr. Muller says this finding can provide insights into research she and other scientists are doing in the field to investigate possible methods for controlling the spread of black band on wild corals. “This is the first study that has looked at ocean acidification on a hard coral disease and I’m sure that we’re going to have many more of these projects to come in the future to see how well we can predict coral disease dynamics changing in this changing world.”
Muller said that overall, coral diseases remain a relatively underexplored field of research. “Coral diseases themselves are still quite a bit of a black box and we’re just trying to even tease apart the major players that could be contributing to some of this mortality,” said Muller.
“Are they bacteria? Are they viruses? Are they fungi? A lot of the times we still don’t know because the marine environment is so dynamic and difficult to work with in a clinical sense,”
In addition to Mote research staff, this study was supported by researchers with the University of South Carolina, and students from the University of Rhode Island, the University of New Hampshire, the University of Hawaii and Unity College in Maine.