COURTESY MICHAEL STAT / HAWAII INSTITUTE OF MARINE BIOLOGY
Diseased table coral sits in waters off the Northwest Hawaiian Islands. UH researchers have found that a variety of algae could weaken coral.
Algae type linked to sick coral
The UH researchers' discovery could help determine whether coral is in danger
Corals in the Northwestern Hawaiian Islands may be susceptible to disease because of a microscopic partner that was thought to be beneficial, University of Hawaii researchers have found.
A particular single-celled algae called dinoflagellate that lives inside the tissue of coral appears to be harming its host, said Michael Stat, assistant researcher in the Hawaii Institute for Marine Biology.
"The relationship between these dinoflagellates and corals has long been considered mutually beneficial, with the dinoflagellates supplying the coral with food via photosynthesis in return for recycled nutrients and shelter," he said.
However, his study, with researchers Ruth Gates and Emily Morris, suggests a type of dinoflagellate doesn't produce enough carbon as a food source for the coral, he said in an interview.
Gates, in a news release, said the discovery will contribute to the conservation and protection of corals. "Just as we have tests for human diseases ... we now have the ability to screen corals for disease susceptibility."
The study was published in a recent edition of the journal Proceedings of the National Academy of Sciences.
Stat said the incidence of coral disease is increasing at French Frigate Shoals in the Papahanaumokuakea Marine National Monument and corals with the same algae in the Florida Keys have been devastated by disease.
A certain type of algae called "clade A" doesn't produce as much food for the coral as other types of dinoflagellates, Stat said. "I think some are more opportunist symbionts (organisms that live in a state of symbiosis). Maybe they are used to living in an ocean environment and keeping all the best food to themselves. They're not sharing."
Through genetic analyses, the researchers were able to identify the type of dinoflagellate in each coral sampled at French Frigate Shoals.
They found healthy coral had one type of dinoflagellate and diseased corals associate with another type that isn't providing any nutrition for the corals, Gates said. As a result, she said, the corals may be starving, making them more susceptible to disease.
In laboratory experiments looking at the amount of carbon produced and released by different coral dinoflagellates, the researchers found the algae in healthy coral produced large amounts of carbon that it released into the outside environment, making it available to the coral as a source of food.
But dinoflagellates in diseased coral produced a small amount of carbon and didn't release any to the outside environment for the coral, they said.