TRAVERSE CITY, Mich. (AP) >> A marine vessel may have caused a leak of coolant fluid from submerged electric cables into the waterway that connects Lake Huron and Lake Michigan, the U.S. Coast Guard said Friday.About 600 gallons (2,270 liters) of a synthetic mineral oil used for insulation escaped into the Straits of Mackinac earlier this week after two power cables owned by American Transmission Co.