Great Lakes invasive species risk increased by US Bill
The Vessel Incidental Discharge Act, a proposed addition to the U.S. defence bill, risks making the Great Lakes highly vulnerable to aquatic invasive species.
The act proposes to exempt ballast water discharges from the federal Clean Water Act. It also would prevent states from adopting new laws to restrict ballast water discharges and enforcing current laws without Coast Guard approval and exempts ships travelling only within the Great Lakes.
Ballast water, taken on board when the ship is travelling light, is discharged near port when cargo is loaded. It is a primary means of transport whereby fish, plants, bacteria and viruses are introduced into areas where they are not indigenous. Aggressive growth of transported species into milder areas can displace local species and grow explosivley, as with Asian Green Mussels which have colonised and blocked water outlets near power stations in the US East Coast. Ballast water discharge is believed to have introduced zebra mussels to the Great Lakes.
Current regulations require ships to exchange ballast water well outside port, to limit the potential spread of invasive species, and new International Maritime Organisation (IMO) regulations are increasing the precautions required. Both the EPA and the IMO are requiring oceangoing ships to exchange ballast water at sea and to install on-board water treatment systems, but the new Act would appear to render their rules meaningless.
Zebra mussel colonies in the Great Lakes have become established in Lake Michigan, Green Bay, the Mississippi River and inland lakes.