2017-11-24 09:07:04
Trilobites: ‘Crazy Jigsaw Puzzles’ Improve Our Views of Coral Reefs

09:07, November 24 67 0

A century ago, if you wanted to document ocean life, you’d throw on a 60-pound glass helmet, dive in and sketch whatever passed by with a lead pencil on a zinc tablet. Today most scientists studying corals still dive with an hour’s worth of oxygen and a plastic piece of paper, using their personal judgments to jot down all they can before the air runs out.

But over the last few years, technology has catapulted oceanography into a new era of discovery. Now a scientist can carry along a camera in a waterproof box, take thousands of photographs an hour and upload those images to computers too fast to exist a decade ago. Powerful software then stitches together the photos and identifies unique features, creating billions of reference points that help to calculate the location of corals in 3D space.

“It’s like doing one of the most crazy jigsaw puzzles you can ever imagine,” said Stuart Sandin, a coral reef ecologist at Scripps Institution of Oceanography at the University of California, San Diego. He and his colleagues have just analyzed some of the first of these 3D photomosaics in a study published last month in the journal, Coral Reefs.

With the help of computer scientists and engineers at their university, Dr. Sandin and his team created their digital maps using more than 39,000 photos of about 44,000 coral colonies living on reefs at Palmyra Atoll near Hawaii. In analyzing digital reconstructions of about 1,000 square feet each, they discovered for the first time that rather than distributing themselves randomly wherever larvae happened to fall, coral follow somewhat of a pattern. Corals of every species and type, especially those that have similar forms and structures, cluster together across the reef. And some types are more clustered than others.

Perhaps the most clustered corals were those with a particular body type that more easily breaks apart with waves or other disturbances and then regrows, like staghorn coral. These corals grow up from the bottom of the reef and stretch out like antlers. They form colonies, “but you can break off one of those antlers and put it somewhere else, and it will grow.”

The scientists think breaking and clustering is how forms of coral such as these hold onto space and survive on a highly competitive reef. They believe it’s a sign of health in this protected atoll, where bleaching, overfishing and disease are not really threats.

To confirm this hypothesis, the research team will compare their reconstructions of the Palmyra Atoll to 99 other reefs in varying states of health in locations across the globe as part of a collaborative, worldwide experiment called the 100 Island Challenge. It aims to create baseline maps and track how reefs are changing over time.

“The 800-pound gorilla is that the climate is changing,” and the prevailing story is that it affects corals disproportionately, Dr. Sandin said. But some corals are doing well and others are recovering. He wants to know where they are and how they’re doing it.

He hopes new data will change public perception that only bad things happen to corals.

The researchers’ finding that corals grow in clusters also has practical applications for conservationists planting corals for new colonies: It’s probably best to plant them in patches.

With time reduced and accuracy improved by technological advances, “It’s an exciting time to see the way that we can explore the ocean,” Dr. Sandin said.