MEMPHIS, Tenn.—River traffic has reopened on the Mississippi River near Memphis, Tennessee, three days after it was closed when a crack was discovered in the Interstate 40 bridge that connects Tennessee and Arkansas, the U.S. Coast Guard said Friday. The Arkansas Department of Transportation, meanwhile, said a video taken by an inspector two years ago found “significant rust and the beginning of a crack” in the same area as the fracture that prompted the bridge’s shutdown this week. More than 60 tugboats hauling more than 1,000 barges were in line Friday to cross under the Hernando De Soto Bridge, the Coast Guard said. Economic development officials had been concerned that an extended closure of river traffic could hurt the region’s economy and have ripple effects on the nation’s supply chain. The bridge itself will remain closed to vehicles indefinitely, with road traffic rerouted to Interstate 55 and the 71-year-old Memphis …