The bioluminescence people find so attractive is a defence mechanism

ONE OF NATURE’S most beautiful phenomena is the nocturnal bioluminescence visible in the world’s oceans, particularly on shores where waves are breaking and in the wakes of moving objects such as swimmers and ships. This ghostly light is produced by single-celled planktonic creatures called dinoflagellates. Ironically, dinoflagellates are also responsible for one of nature’s nastiest phenomena—red tides. These are water-discolouring, toxin-generating blooms of the organisms. The toxins kill fish and other large wildlife. And they accumulate in filter-feeding bivalve molluscs of the sort that end up on dinner tables, to the serious detriment of the diner.Toxin-generation is clearly defensive. The purpose of bioluminescence is less clear. But many of those who think about such matters suspect that it, too, has a defensive purpose. And work just published in by Erik Selander and Andrew Prevett of Gothenburg University, in Sweden, confirms that hypothesis.