Since coral reefs are a phenomena of tropical waters, wouldn't it make sense that increased water temperature would increase the area where coral growth is viable?
I think the comment about corals would make sense if both growth and death occurred at the same rate. But it doesn't. It takes coral and awful long time to establish itself and grow, but you can have a massive die-off in a single season. So we're starting to see some large die-offs in warmer waters. Maybe in a few hundred years it will balance out, but that's not really too comforting if you are dependent on fish now that lives off of the coral.