Coral reefs can resemble underwater monuments, with strong towers and meandering walls that stand firm against the tides. But a new study says that if global warming causes ocean water to become more acidic those elaborate structures may crumble because the cement-like binding agent that holds the reefs together won't be able to form in those inhospitable waters. Most of the world's coral reefs aren't yet showing signs of this degradation, as ocean pH is slow to change and reefs form slowly. But researchers got a chance to peer into the possible future in