CHICAGO (Reuters) - Ships entering the Great Lakes should be made to kill all the creatures that hitch a ride in their ballast tanks, environmental groups said on Tuesday, challenging as too lax a proposed government standard to combat invasive species.
Zebra mussels, spiny water fleas, round gobies and other invaders brought into the lakes in ships' ballast water have damaged the Great Lakes' $7 billion fishery and allowed algae - some that produce toxins that foul the world's largest body of fresh surface water - to flourish.
Researchers at the University of Notre Dame put the annual cost of dealing with invasive species such as clearing mussels from clogged water intakes at $200 million. The mussels and other invaders have filtered out plankton at the base of the food web, hurting lake fish species and allowing more sunlight to fuel algae growth.
Environmental groups said they may go to court for a fourth time since the 1990s to get the U.S. Environmental Protection Agency to tighten its restrictions on ballast discharge.
EPA is under court order to rewrite its 2008 ballast tank rule this year, with the rule to take effect in 2013. The agency has proposed adopting steps on ballast tanks that are recommended by the United Nations' International Maritime Organization, which call for some treatment of discharged water.
"The EPA's new proposed permit isn't tough enough to prevent the next harmful invader from slipping into our waters," said Thom Cmar of the Natural Resources Defense Council.
Several technologies exist to treat ballast water, which Cmar said are similar to municipal wastewater treatment that cleans water with chemicals, ultraviolet light, or filtration systems. He said it would cost less than $1 million to outfit a typical cargo vessel.
The current EPA standard requires ocean-going ships bound for the Great Lakes to exchange their ballast water with salt water while at sea -- dubbed "swish and spit" -- that is supposed to kill freshwater species in the tanks. But muck and pockets of fresh water in the tanks can harbor invaders, Cmar said.
The groups urged zero tolerance for invasive species in ballast water to be discharged in the Great Lakes. They also want ballast treatment for ships that never leave the lakes but can spread already established invasive species.
Cmar said regulators need to apply a different standard for invasive species than they do for pollution. Reducing, but not eliminating, species could still prove disastrous if surviving creatures find each other and propagate.
A recent scientific survey in Duluth, Minnesota's harbor on Lake Superior found eight new invasive species, Marc Smith of the National Wildlife Federation said. But there is no active ongoing search for new invaders in the Great Lakes, the environmental groups said.
There is a considerable federal effort under way to keep out invasive Asian Carp that are working their way up to the lakes from the Mississippi River basin.
(Reporting by Andrew Stern; Editing by Jackie Frank)