Even the depths of the oceans can't escape the harmful effects of global warming and that includes corals, researchers have found. Corals play an important role in the marine life, providing food and shelter for fish. Sea sponges contain anti-cancer agents among the corals. By the end of this century, as more carbon dioxide is released and the oceans become more acidic, only 30 percent of those waters are expected to still be supersaturated. Many of the deep-sea coral reefs were undiscovered until the past 15 to 25 years. More carbon dioxide leads to a reduced supply of calcium compounds used by corals and other marine creatures to build their shells.