in the last 25 years, we've seen a big shihift from what we ththk of as coral reeeefs to algal meadowows. narrator: since 1974, phil dustan has documented the demise of the once vibrant coral reefs along the florida keys and the cariribbean islands.s. dustan us photographphy, transect measurements, a species checklist, and continuous water temperature monitoring. on bali's menjangan reef, dustan worked with coral reef sentist carol milner. milner: the biodiversity in this area of southeast asia, within the cocoral triangle, is the higighest in the world. we started this reef in 2011 and again in 2016 to make an objective, unbiased comparison of the reef at those times. we've used transects, so we lay a 50-meter tape measure, and every 50 centimeters, we record the substrate directly below-- whether it's live coral, whether it's dead coral; whether it's rock or sand, whether it's algae--to as much detail as we can. so for every tape measure we lay, we get a hundred points, and we can work out a percentage of coverage. we also go along one meter either side of that tape measure, so it's a