KEY WEST, FLA. – Since the 1970s, Billy Causey has observed ominous signs of change in the coral reefs of the Florida Keys. As southeast regional director for the National Marine Sanctuary Program of the National Oceanic and Atmospheric Administration, Causey has a front-row seat.

He has spent decades diving on Florida’s coast, where he has witnessed effects of warming waters and ocean acidification on reef ecosystems. (Click below to see a three-minute video interview with Causey.)

“I think in our lifetime, we’re going to have to be prepared to see corals change,” Causey said. “The fact that corals are telling us ‘Change is coming’ is something we need to be paying attention to.”

At his seaside office in Key West, Sara Peach talked with Causey about how corals are changing … and why most tourists do not notice the difference.

Editor’s Note: This video essay is one part in a continuing Yale Forum series on climate change impacts on oceans and ocean ecosystems. The September  27, 2009, update to The Yale Forum includes freelancer Mark Schrope’s update on ocean acidification research and monitoring.  His earlier piece on the state of coral reefs is available here. An earlier piece focusing on the basic chemistry of ocean acidification, posted in June 2008, was written by Marah Hardt and Carl Safina.

Sara Peach is a multi-media environmental journalist living in Carrboro, North Carolina.