TALLAHASSEE, Fla. – A first of its kind assessment of coral reefs in U.S. waters is again sounding the alarm over the continued decline of these sensitive underwater ecosystems, which scientists deem essential to the health of the world's oceans amid the environmental effects posed by human activity and climate change.The report, released Tuesday by the National Oceanic and Atmospheric Administration and the University of Maryland, took stock of the health of coral reefs under U.S.