Coral reefs are found only in a band that extends along the equator, from about thirty degrees north to thirty degrees south latitude. At these latitudes, there’s not much mixing between the top and the bottom layers of the water column, and essential nutrients, like nitrogen and phosphorus, are in short supply. (The reason the water in the tropics is often so marvelously clear is that little can survive in it.) How reefs support so much diversity under such austere conditions has long puzzled scientists—a conundrum that’s become known as “Darwin’s paradox.” The best answer anyone has come up
...more
