The US navy set off a massive explosion last week, detonating a 40,000lb blast as part of a test to determine whether its newest aircraft carrier, the USS Gerald Ford, is ready for war. The test, known as a full ship shock trial, is just the first of three planned blasts over the coming months.
But the amount of explosive used – 40,000 lbs – is enough to have outsized effects on any marine life in the area, said Michael Jasny, who directs the Natural Resources Defense Council’s Marine Mammal Protection Project, working on the law and policy of ocean noise pollution.
Ordinarily, the navy uses much smaller detonations in sinking exercises, just a fraction of this size, he says.
“The navy’s own modeling indicates that some smaller species of marine mammals would be expected to die within 1-2km of the blast, and that some marine mammal species would suffer injury including hearing loss out to 10km of the blast. That gives some sense of the power of the explosives we are talking about,” Jasny said.
It’s difficult to monitor marine mammals even in the best of conditions, as they spend most of their lives underwater – but the navy doesn’t use trained biologists to do the monitoring, so it’s hard to say what the true impacts will be.
“This is unfortunately a black box of an exercise,” Jasny said. “We don’t know how conscientiously the blast site was chosen, and we don’t know how effective the monitoring was before the detonation, so it’s hard to put a great deal of faith in the safety of marine life.”
The area is home to populations of dolphin and small whales at this time of year, and Jasny says that’s worrisome because as a general rule, smaller animals are more vulnerable to blast injury.
“A large whale might need to be within a few hundred meters of the blast to die, while a small mammal could be a couple of kilometers away,” he said, adding that even if the animals survive, loss of hearing is a significant problem for mammals who make their living in the ocean, as they use their hearing to find food and find each other.
Images and video footage from the most recent blast showed a gigantic plume of water shoot from the ocean as a result of the test, and the US Geological Survey said the explosion, which took place in the Atlantic Ocean about 100 miles off Palm Coast, Florida, registered as a 3.9 magnitude earthquake on the coastline.
A spokesperson for the USS Gerald Ford, a nuclear-powered carrier, told Defense News that the test took place “within a narrow schedule that complies with environmental mitigation requirements, respecting known migration patterns of marine life in the test area”.
These blasts are just the tip of the iceberg for navy activity – while these are huge explosions, each year the navy will detonate thousands of explosives in its more heavily-used ranges off the south-eastern coast of the US, or off of southern California.
“None of those are of the power used in a shock trial, but many of them, hundreds of them, are of a power sufficient to kill marine mammals,” Jasny said.