We’re in the midst of the International Year of the Reef, but there’s little to celebrate: Nearly half of coral reefs in U.S. waters are in “poor” or “fair” condition, the National Oceanic and Atmospheric Administration reported at this week’s 11th International Coral Reef Symposium. Human activity messes with reefs in all sorts of ways, from ocean acidification (spurred by carbon-dioxide emissions) to fishing, boating, diving, marine debris, coastal development, pollution, erosion, and smothering seaweed grown for human consumption. Two coral species — elkhorn and staghorn — are listed as endangered. And loss of coral doesn’t just mean disappointed snorkelers: one-quarter of all marine species rely on coral in one way or another, and 40 percent of fish with commercial value breed in reefs.