Marine biology: animal, mineral, plant?

Corals may resemble beautiful marine plants, but, explains Dr Brian Roy Rosen, they are stinging walls of death for small organisms

The Biologist Vol 62(3) p12-15

How to categorise corals has teased enquiring minds for thousands of years. They have stony, mineral skeletons of calcium carbonate, in effect limestone, and are technically animals. But underwater they resemble shrubs or even flowers, and the cells of many species contain algal symbionts, which make them dependent on light, like plants. This is why they grow in elaborate plant-like shapes to maximise light capture.

Coral reefs are home to almost a quarter of all living marine species, and more than 500 million people depend on them for food, coastal protection and tourism. Yet global warming, pollution, overfishing and possibly ocean acidification are killing coral reefs. One in four of the world's coral reefs are dead and many more are threatened.

Apart from specialists, few people in Britain understand coral or its importance, so it is timely that this summer there is an unprecedented exhibition at the Natural History Museum in London called Coral Reefs: Secret Cities of the Sea.

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