Sun.

Maybe one of the more important things you'd see today:
http://www.thesolutionsjournal.com/node/237326

Sadly, in the past 30 years, 25-40 percent of all corals worldwide and 92 percent of the branching corals indigenous to Florida and the American Caribbean have perished due to climate change, pollution, ocean acidification, and disease.² With such disturbingly low numbers remaining, recovery without help from humans is extremely unlikely and probably would not occur in our lifetime.