Michigan loses new request in Great Lakes carp case

* High court won't order closing of two Chicago-area locks

* New request made after carp DNA found in Lake Michigan

* Federal government opposed Michigan's new motion

By James Vicini

WASHINGTON, March 22 (Reuters) - The U.S. Supreme Court on Monday rejected another request by the state of Michigan for an order to close two Chicago-area waterway locks to keep Asian carp from invading the Great Lakes.

The high court turned down Michigan's initial request on Jan. 19 but the state filed a new motion after the discovery of carp DNA in water samples taken from the Calumet Harbor on Lake Michigan, at the mouth of the Calumet River.

Two species of Asian carp -- the voracious Bighead and Silver carp, which can grow to 5 feet (1.5 meters) and 100 pounds (45 kg) -- are considered a threat to the lakes' $7 billion fisheries. Scientists fear they would consume plankton and other small life forms, crowding out other species of fish.

The federal government, the state of Illinois and Chicago's sewer authority opposed Michigan's initial request on the grounds that closing the locks could cause massive flooding and hurt shippers by preventing the continued navigation of vessels on the Chicago waterway system.

In its second request Michigan said the locks would be temporarily closed except in cases to protect public health and safety, such as preventing flooding or allowing the passage of vessels for emergency purposes.

The state's preliminary injunction request also sought other steps, including a new temporary barrier to block fish from entering the Little Calumet River and measures to capture, kill or curtail the movement of Asian carp in the waterway.

U.S. Solicitor General Elena Kagan opposed the request, telling the Supreme Court an injunction could "substantially affect the regional and national economies and greatly disrupt transportation systems on both land and water on which those economies rely."

The court denied the state's motion in a one-sentence order. Michigan still has pending before the Supreme Court a separate request to reopen cases dating to the 1920s about water flows involving the Chicago River and Lake Michigan.

Three environmental groups and the state of Indiana are urging the court to take up that case. The environmentalists say the carp, which have come to dominate sections of the Mississippi and its tributaries, could potentially devastate a $7 billion fishery in the Great Lakes and severely impact the lakes, which hold one-fifth of the world's fresh water. (Additional reporting by Andrew Stern in Chicago; editing by Bill Trott)