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What’s wiping out the Caribbean corals?

by Angela Herring

Here’s what we know about white-​​band dis­ease: It has already killed up to 95 per­cent of the Caribbean’s reef-​​building elkhorn and staghorn corals, and it’s caused by an infec­tious bac­teria that seems to be trans­mitted through the water and by coral-​​eating snails.

Here’s what we don’t know: every­thing else.

But two student-​​researchers working in North­eastern asso­ciate pro­fessor of marine and envi­ron­mental sci­ence Steve Vollmer’s lab are trying to change that: Sarah Gignoux-​​Wolfsohn, a fourth-​​year doc­toral can­di­date, and under­grad­uate Felicia Aronson, S’16, an envi­ron­mental sci­ence major with a con­cen­tra­tion in marine sci­ence. Together, they are using the resources they raised from a crowd­funding sci­ence cam­paign to figure out what’s killing the Caribbean corals.

“Before this, we knew that white-​​band dis­ease was caused by a bac­teria, and we had a list of poten­tial pathogens,” said Gignoux-​​Wolfsohn, noting that these find­ings emerged from pre­vious research at Vollmer’s lab. The pathogen list was the product of a large-​​scale genetic sequencing analysis led by Gignoux-​​Wolfsohn. Now she and Aronson have launched a sys­tem­atic research pro­gram to sift through that list in the hopes of iden­ti­fying the culprit.

Working at the Smith­sonian Trop­ical Research Insti­tute in Bocas del Toro, Panama, Gignoux-​​Wolfsohn and Aronson spent the month of June per­forming a series of exper­i­ments in which they admin­is­tered var­ious antibi­otics to dis­eased coral slur­ries con­tained in bench-​​top aquar­iums. Antibi­otics kill dif­ferent bac­te­rial types, so when healthy corals con­tract the dis­ease despite treat­ment, the team is able to home in on the char­ac­ter­is­tics of the cul­prit bacteria.

They also per­formed an opposing exper­i­ment in which they exposed healthy corals to dis­ease slur­ries grown in dif­ferent envi­ron­mental con­di­tions that select for dif­ferent bac­teria to see if they con­tract dis­ease. “If we grow a spe­cific group of bac­teria and it still trans­mits the dis­ease, we know the pathogen is likely in this group,” Gignoux-​​Wolfsohn explained.

The student-​​researchers raised their funding goal of $3,180 in just three days through exper​i​ment​.com, marking the third fastest suc­cess story in the crowd­funding website’s his­tory. Upon reaching that goal, they extended their cam­paign to more than double the orig­inal amount, which they also raised in record time.

Backed by this finan­cial sup­port, Gignoux-​​Wolfsohn and Aronson brought bac­te­rial sam­ples back to Boston, where they will now begin per­forming exhaus­tive genetic analyses. “Right now is a really cool time to be addressing these issues because we have a lot of emerging genetic tech­niques that people are just starting to use to ask ques­tions about the micro­bi­ology of corals,” Aronson said.

They’re using those tools to under­stand how the dis­eased coral com­mu­nity is dif­ferent from the healthy com­mu­nity in ways that haven’t been pos­sible before. The approach is some­what novel in the field of marine ecology, Gignoux-​​Wolfsohn said, and it’s part of why she’s doing it. As an under­grad­uate at Wes­leyan Uni­ver­sity, she studied blood-​​vessel for­ma­tion using genetic-​​based tech­niques. “I wanted to take those skills and apply them to a more con­ser­va­tion and ecology based research pro­gram,” she explained.

Originally published in news@Northeastern on July 31, 2014.

College of Science