(MN) Pioneer Press - Eight Minnesota environmental and conservation organizations are urging the U.S. Coast Guard to adopt tougher ballast-water standards for ships on the Great Lakes to stop the introduction and spread of harmful invasive aquatic species.

In a letter to the Coast Guard this week, the groups said the first step of a proposed rule is too weak and takes too long to put into place. They said that it must be effective in killing even small organisms in the ships’ ballast water and that the deadlines should be moved up. More