Particle paths are shown in gold and green; coral polyps are pink and purple Vicente Fernandez

You are looking at a sea of small-scale activity surrounding a reef-building coral. The intricate, swirling patterns in the water are made by cilia: hair-like appendages which move in unison as the corals breathe, feed and clean themselves. To understand how corals engineer their environment, researchers from MIT's Environmental Microfluidics Group and the Weizmann Institute of Science in Israel examined the cilia-filled valley between two 3mm-wide cauliflower coral polyps under a microscope; they then added powdered food to the water to see how the cilia affect its flow. “This project helps us understand how corals might respond to changes in their environment,” says engineer Vicente Fernandez, a postdoctoral associate at the MIT lab. "It demonstrates that these vortices are not ephemeral and can substantially affect the coral environment."

The researchers examined how flow patterns change at 90-minute intervals, then condensed the data into a single time-lapse image. The original stills were shot in greyscale, with artificial colour added for contrast. “We were hoping to give a perspective into the life of coral,” says Fernandez, “and to reward close scrutiny, so the scientific facet of the image remained prominent.”