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Coral bleaching and disease have made headlines for decades- and with good reason. FIU researchers have proposed an idea on the topic that will open the floodgates for questions that, until now, have not been explored.

Our very own Marine Sciences Program Ph.D. Candidate, Daniel Merselis, and his team tracked 152 individual corals through the 2014 coral bleaching event in a coral restoration nursery. They found a highly significant negative correlation between coral bleaching and disease- contradicting what scientists have observed until now.

Working under FIU Tropics’ Dr. Rodriguez- Lanetty, Merselis proposed a hypothesis for the mechanism behind his surprising results, suggesting that bleaching-resistant corals may be at greater risk of tissue loss disease.

“We suggest that it might be possible for coral bleaching, by temporarily removing these extremely helpful foreign microbes, to actually free up the immune system to work at full strength,” explains Merselis.

Coral bleaching results from the breakdown of the relationship between a genus of dinoflagellates, referred to as Symbiodinium, and reef-building corals. Coral bleaching is linked to increased water temperature. Similarly, coral tissue-loss disease outbreaks are linked to thermal stress and poor water quality, and often follow bleaching events. Despite this trend, scientists have struggled to determine whether this relationship between bleaching and disease is causal or correlational.

Across populations, when Symbiodinium is removed from corals as a result of bleaching events, an increase in disease follows. Merselis’ study however, had one key difference: they studied individuals. In studying individual corals and recording data at multiple time points of the study, the team discovered the exact opposite- bleached corals maintain their immunological integrity and therefore experience less disease, while bleach resistant corals are immunologically suppressed.

“Coral reefs provide a home to more than 25% of all marine species and they’re vital to South Florida’s economy, but we’re losing them rapidly as our oceans continue to warm. By identifying vulnerabilities and strengths of many [coral] strains, our work suggests that selective breeding of these corals could both bolster strengths exhibited by the more resistant strains and rescue valuable genetic information from the “weaker” strains,” urges Merselis.

It is the hope of Merselis and his team that their study will lead to new, innovative research that will offer hope for coral reefs

Read the full study to learn more.