The world's largest marine reserve established at Hawaii
Using his Constitutional power to designate national monuments, President Obama has created the world's largest protected marine area at Papahanaumokuakea Marine National Monument by more than quadrupling its size from 138,900 to 582,578 square miles (1,510,000 square kilometers).
The coral reefs at Papahanaumokuakea Marine National Monument, established by President Bush in 2006, is home to many Hawaiian endemics. It is a UNESCO-designated World Heritage site.
In 2015, Palau declared 193,000 square miles of marine protected area (MPA). If this is sign of upcoming global MPA upsmanship, we welcome it! It's your turn, Australia. The Great Barrier Reef's MPA is only 133,300 square miles.