One of the biggest threats to aquatic ecosystems in the United States--and to the Great Lake's in particular--is the introduction of foreign species (everything ranging from plants, to fish, to microscopic organisms) into our waters by transoceanic ships. These vessels take on huge quantities of water to adjust their trim and increase their stability in open ocean. When they get to a port in the United States, that water (and all the critters still living in it) is then flushed so the ship can take on cargo. 
The result has been an explosion in the introduction of invasive species into the Great Lakes and other coastal regions. According to a report by the Environmental Protection Agency, the introduction of the zebra mussel alone has caused an estimated $5 billion dollars in damages to water pipes and other hard surfaces in the Great Lakes. And the San Francisco Bay-Delta ecosystem has been invaded by 230 non-native species. More than 10,000 species may be transported across the world's oceans in the ballast water of ships each day.
Which is why it was good news when the Congress started to seriously consider establishing tough national standard for the treatment of ballast water discharges in the United States. Unfortunately, like most things in Congress, there's a catch. Pressed hard by the shipping industry, committees in both the House and Senate have passed bills that not only establish a minimum treatment standard for ballast water, but would short circuit other efforts to regulate ballast water--specifically regulations just now being drafted by the Environmental Protection Agency as well as all state laws (California and Michigan have them on the books already) that also seek to deal with the problem of ballast water.
Luckily, Senator Barbara Boxer, chair of the Senate's Environment and Public Works Committee, and other legislators have made clear that they're not going to stand idly by while the Clean Water Act and state law is gutted. We'll be supporting her efforts not only to establish strong minimum treatment standards, but also to protect our bedrock environmental laws in the process.