Edward Willett

Disease-Hunting Scientist: Dr. Laurie Richardson and black-band disease in coral

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My newest book, Disease-Hunting Scientist (Enslow Publishers) has now been officially released, and so this week I’m giving you a column-sized version of another of the lengthy chapters devoted to individual scientists in the book.

Dr. Laurie Richardson, Professor of Biology at Florida International University in Miami, is researching black-band disease in coral reefs—which means she spends a lot of each summer scuba-diving, often for hours a day.

At 287,231 square kilometers, coral reefs are less than a tenth of a percent of the total ocean floor. But they support more than a million species of marine life. They are also dying, from pollution, overfishing—and black-band disease, among others.

Dr. Richardson started her career researching “microbial mats,” communities of microbes that live in the sulfur-rich water of hot springs. She then worked in Wisconsin on a NASA project that used satellite data in the study of aquatic ecosystems. That led to three years at NASA’s Ames Research Centre in California learning remote sensing and image processing, which in turn landed her in Florida with a NASA-funded grant to work on algal pigments and remote sensing.

One day, while she was diving for fun on a coral reef, somebody showed her an example of black-band disease-and she immediately recognized it as similar to the microbial communities she’d studied in hot-spring outflows.

She looked in the scientific literature, and no one else had made that connection. And that was how the research she’s now been doing for more than 15 years began.

Like most scientists, Richardson spends most of her time writing papers and proposals, teaching, or in her laboratory, but about ten percent of the time, mostly in the summer, you can find her diving with graduate students, undergraduate students, and research collaborators, collecting samples and monitoring the progress of disease on the reef.

Coral samples are taken with numbered, sterilized syringes. The divers record on underwater slates the number of the syringe, what the sample is, and a description of the diseased coral. Evenings of the ten-day-long diving expeditions are typically spent transcribing information from the underwater slates into a database or field notebook.

Most of the time the diving itself is fun. But not always. On one occasion, Richardson suffered the bends (an extremely painful condition caused by bubbles of dissolved nitrogen forming in the bloodstream as the diver surfaces). On another, a sudden strong underwater surge reduced visibility to nothing and threatened to sweep her and her students away from the boat into the Gulf Stream.

Corals consist of an extremely thin layer of living tissue (often less than a millimeter thick) over a rock-like skeleton of calcium carbonate. A lot of bacteria live in association with the coral’s surface and can cause a really nasty infection in any cut. Fortunately, Richardson has avoided that particular hazard so far.

As for black-band disease, Richardson says it’s now like a jigsaw puzzle that is maybe seven-eighths of the way filled in. “Anything we figure out now is one more piece of the puzzle, so that is really exciting.”

She’s figured out that as the disease-causing community of bacteria (dominated by blue-green algae) first grows, it consumes the available oxygen, opening the door for another group of bacteria that thrive in an oxygen-free environment, instead using sulfate dissolved in the water. Those bacteria produce sulfide gas as waste, killing coral tissue, which is then devoured by additional bacteria.

Contributing to the problem: a warming ocean. Corals like warm water, but not too warm. For microorganisms, on the other hand, the warmer, the better. As a result, the growth of bacteria and blue-green algae “takes off like a rocket” at the same time that the corals they are living on become stressed. The result is disease.

Richardson’s work may also shed light on human diseases, because many human diseases are also caused by a community of bacteria. In fact, her current funding is from the National Institutes of Health.

And finally, it’s a wonderful teaching model. “I’m a biology professor, and my students are learning all about ecology and physiology and microbiology and molecular genetics while they’re out there in this incredible environment working on the reef.”

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