Coral reefs, deep gardens, and rolling rocks
A purple rhodolith from Fiji. Three ways to build a reef Check out this knobbly pinkish lump about the size of a golf ball, and another one over here about the size of my fist. It feels like a rock and looks like one. But it is alive. It has been growing, very slowly, for decades or even centuries, and while you were holding it, you may have disturbed a dozen small animals living in its cracks and tunnels. You picked up a rhodolith, and if you really found one on a beach, you would probably not even notice it. Some of the most important habitats in the ocean are built by organisms that turn seawater into stone. They pull calcium and carbonate from the water, lay down a hard skeleton, and leave behind structures that other organisms use for feeding, hiding, and raising young. These are ecosystem engineers that build reefs. A reef: a bright, shallow tropical coral reef full of fish. Familiar, but that is only one way to build a reef. Herein, I want to look at three: tropical coral ...