Microscopic pathogens have been causing mass coral die-offs around the world. But now researchers are using high-speed video to spy on the behavior of killer microbes and potentially learn how to better manage coral disease.
For the past two decades corals have been dying from infections, ocean pollution and increasing temperatures. Without a way to see corals at a microscopic level, no one knows exactly how they get sick, which microbes help them stay healthy, or what we can do about it.
Corals are "complex beasts" with lots of algae, bacteria and viruses hanging around them, said Garren, the marine microbiologist at MIT performing the research. Most ocean microbes won't even grow in a petri dish, so she's gone way beyond traditional lab techniques to observe live corals and their associated bugs.
To learn if a bacterium that turns up near dead corals makes it to the animal's surface, Garren used a type of biomedical imaging that can pick up different-sized microbes and the coral's complex structure. After exposing live corals to the bacterium in the lab, a laser scanning confocal microscope
let her see bacteria marked with a blue dye settled among the naturally florescent green coral polyps.
The bacterium, Vibrio coralliilyticus, is related to the pathogen that causes cholera. It bleaches corals and can make their cells explode. Until now, most people assumed the bacterium just floated around and landed on corals by chance. Instead of aimless drifting, bacteria speed toward coral mucus at 100 body lengths per second. The photo to the right shows the bacteria as green specks.
Garren is now working out exactly what attracts the microbes to the coral's mucous cocktail and whether different temperature and nutrient conditions change the bacterias response. She hopes to discover what climate change and coastal pollution look like in the ocean's microscopic world, and ultimately how to manage it.