Sea Urchin Reef Concert

Auckland University marine biologists Craig Radford and Andrew Jeffs have discovered that sea urchins are behind loud noises emanating from underwater around New Zealand reefs. The 20- to 30-decibel sound is caused by the spiny sea creatures’ teeth scraping on reefs as the hungry starfish relatives feed on algae and invertebrates. Radford said urchins had long been suspected of creating the din, but it took a series of experiments to confirm it. “We put some urchins in a tank and got them feeding on algae, then we recorded them. The noise they were producing caused spikes at certain frequencies,” he said. Coastal noise of similar frequency and bandwidth has been recorded near the Bahamas; San Diego, California; and Australia. Chris Tindle, a physicist at the University of Auckland, said the urchins made more noise on dark nights around the new moon.