Jean-Baptiste Lamarck was one of the earliest scientists to study corals in the 19th century. One of the mysteries that has endured since then is why some of them pulsate. This movement, in which their flowerlike heads open and close, requires a lot of energy, so there must be a good reason for it. In jellyfish, the only other creature that pulsates in the same way, it’s used for movement and catching prey, but corals do neither of those things.
Scientists using infrared cameras found that the corals pulsate 95 percent of the time, resting only for about half an hour in the afternoon. By using a special imaging device that allowed researchers to see the movement of water down to individual particles, scientists discovered that the movement stops waste water from building up around the corals. They also found that the oxygen levels in the water around corals were kept low by the movement, increasing the efficiency of photosynthesis in algae that the corals use for food.