Several sported long, fragile spines, which interlocked with those of their neighbours as they tumbled together. Their crystal surfaces reflected and refracted the light, creating flashes of green, red and blue in a golden setting. The general consensus now is that the spines make diatoms more likely to be caught by small currents, bringing them constantly into contact with fresh water and essential nutrients. Another theory is that protuberances and long chains defend diatoms against predators. Some diatom species produce highly potent toxins, which can kill shellfish and fish, and become concentrated along the food chain, eventually causing gastrointestinal and neurological illness in whales, porpoises, seabirds and humans.
Diatom blooms are impressive affairs.
Individual cells may grow and divide as often as once a day, until one or several of the key nutrients they need becomes depleted. This can trigger a population crash, and diatoms then rain out of the surface waters - a bizarre effect referred to as 'marine snow'. Not all diatoms live among the plankton. Some dwell in soils, growing when the earth is moist and tolerating drought for long periods of time. Others grow on the leaves of trees in the tropics and even on the feathers of seabirds.