TRAVERSE CITY, Mich. (AP) — Oceangoing cargo ships will be required to zap their ballast water with ultraviolet light, chemicals or other treatments before dumping it in U.S. waters under a regulation the Coast Guard announced Friday to prevent species invasions that damage the environment and cause billions in economic losses.

The long-awaited rule comes more than two decades after environmental groups began pushing for a crackdown on ballast water, which provides stability in rough seas but often harbors stowaway species from abroad. When the soupy mixtures of water and sediment are discharged in U.S. ports, the newcomers can spread rapidly, starve out native competitors and spread diseases.

Zebra and quagga mussels that hitched a ride to the Great Lakes from Europe in the 1980s have clogged water intake pipes, requiring expensive repairs, and are blamed for a Lake Huron salmon collapse and botulism that killed thousands of shore birds. Other invaders that arrived in ballast tanks include Asian clams in San Francisco Bay, Japanese shore crabs along the Atlantic coast and spotted jellyfish in the Gulf of Mexico.

“Once fully implemented, this ballast water discharge standard will significantly reduce the risk of an introduction of aquatic nuisance species into the Great Lakes,” said Rear Adm. Michael Parks, commander of the Coast Guard’s Cleveland district.

Under existing rules, shippers must exchange ballast at sea or flush the tanks with salt water if empty. But the Coast Guard acknowledged some organisms could survive in puddles of water and mud. For the first time, the new policy requires onboard treatment of ballast water to kill as many fish, mussels and even tiny microbes as possible.

“It’s a major milestone and a starting point, but it’s not nearly as strong as it should be,” said Jennifer Nalbone of Great Lakes United, a U.S.-Canadian advocacy group.

The rule limits numbers of living organisms in particular volumes of water. Ships would have to install equipment to meet standards developed by the International Maritime Organization, an arm of the United Nations. Environmental groups contend the limits should be 100 or even 1,000 times tougher, but industry groups say no existing technology can do that.

A tentative version of the Coast Guard rule issued in 2009 called for starting with the international standard, then making it 1,000 times stronger by 2016. But the final regulation drops the second level in favor of more research.

The Coast Guard said it made the change after an Environmental Protection Agency study questioned the reliability of more stringent standards. EPA has proposed a separate ship discharge policy based on the international limits.

In a written statement, the Coast Guard said it “fully intends to issue a later rule that will establish a more stringent phase-two discharge standard.”

Thom Cmar, an attorney with the Natural Resources Defense Council, said the delay was a step backward.

“For them to say they’ll get back in a couple of years with an analysis of whether a stronger standard is achievable is cold comfort after it’s taken so long to finish this round of rulemaking,” he said.

Cmar also criticized a decision to exempt ships that remain within the Great Lakes from the ballast standards. Environmentalists contend those ships carry invasive species around the lakes even if they weren’t responsible for bringing them to the U.S. The Coast Guard said research is needed into whether existing ballast technology would work on vessels that never travel the oceans.

Shipping interests were unhappy the Coast Guard dropped an earlier provision exempting vessels fitted with ballast treatment systems from having to modify them if standards are toughened in the future.

But completion of the rule is mostly good news for ship owners who have delayed installing equipment until they knew what would be required, said Steve Fisher, executive director of the American Great Lakes Ports Association.

“This will create a huge international demand for ballast water treatment equipment,” Fisher said. “Companies that manufacture it will be able to justify spending the money for mass production. The most viable and cost-effective systems will float to the top.”

Posted 3/20/3012