Two AV-8B Harrier involved in the Talisman Sabre joint military exercise in Queensland's Shoalwater Bay dropped a jettison box after a live-fire mission was canceled after several attempts to drop the bombs on a range on a nearby island.
The U.S. Navy said it was looking into how it could retrieve the bombs. Pilots on the Marine planes chose a spot far away from the reefs to jettison the bombs, 50 to 60 meters down, which was deep enough so they would not be disturbed by passing ships.
"The jettison box was selected in a deep channel away from the reef to minimize the possibility of reef damage," a Navy official said. "However the inert and unexploded ordnance is inside the Great Barrier Reef World Heritage area."
"The Navy knows full well how environmentally sensitive the Great Barrier Reef is, and will do everything to make this right," the official said
Two of the bombs were explosive but disarmed before they were dropped. The others were inert, the Navy said, and none of the bombs exploded and posed no threat to the public or the reef.
The Great Barrier Reef is home to 400 types of coral, 1,500 species of fish and 4,000 kinds of mollusks, some of which are threatened by extinction.
Australian lawmakers reacted with outrage over the news.
"I think it's outrageous that we're letting the US military drop bombs on the World Heritage Great Barrier Reef," said Greens Senator Larissa Waters. "I mean, have we gone completely mad? Is this how we look after our World Heritage area now? Letting a foreign power drop bombs on it?"
About 28,000 American and Australian military forces are involved in the Talisman Sabre exercise, going from July 15 to August 5.