The swirling patterns moving around these coral polyps may look like fireworks streaking across a long-exposure photograph, but they are the result of a cunning technique that uses false colours to help compress time and movement into a single picture.
The image shows two Pocillopora damicornis polyps roughly 3 millimetres apart, coloured pink. To reveal how the corals’ wafting cilia beat the water into a vortex, the team tracked particles in the water by video and super-imposed successive frames to highlight the flow (gold). About 90 minutes later, the coral polyps have changed position (shown in purple), altering the water flow (cyan), “but the vortex stayed roughly the same,” says Massachusetts Institute of Technology environmental engineer, Vicente Fernandez, part of the research team that produced the image. The spacing between points in the vortex tracks even reveals the speed of the particles
Vicente added “Up close you can see the steps of individual particles, see where the flow is strongest.”
He says that the team drew inspiration from the palette used by Andy Warhol in his Flowers prints, which feature vivid, strongly contrasting colours.
The vortex helps draw nutrients toward the coral and sweep away waste products, says Fernandez’s colleague, Orr Shapiro, an ecologist at the Weizmann Institute of Science in Rehovot, Israel.
“Everywhere I look at corals now I find these vortical swirls,” he adds.
“This was a unanimous winner,” says judge Alisa Zapp Machalek. “It’s a striking image—but it also represents an aspect of nature that, to our knowledge, had never been captured before.”
The image was a winner in the 2013 International Science and Engineering Visualization Challenge and currently features on the cover of Science magazine.