“Tropical waters tend to be low in nutrients, like nitrogen and phosphorus, which are crucial to most forms of life. This has to do with what’s called the thermal structure of the water column, and it’s why tropical waters are often so beautifully clear. As a consequence, the seas in the tropics should be barren—the aqueous equivalents of deserts. Reefs are thus not just underwater rain forests; they are rain forests in a marine Sahara.”
“The first person to be perplexed by this incongruity was Darwin, and it has since become known as “Darwin’s paradox.” [The paradox] has never been entirely resolved, but one key to the puzzle seems to be recycling. Reefs—or, really, reef creatures—have developed a fantastically efficient system by which nutrients are passed from one class of organisms to another, as a giant bazaar. Corals are the main players in this complex system of exchange, and, at the same time, they provide the platform that makes the trading possible. Without them, there’s just more watery desert.” —The Sixth Extinction
Water Literacy Primer 