Fear of litterbugs prompted officials to make several islands in Biscayne Bay off limits during the Fourth of July holiday. City of Miami officials said Osprey, Morningside, Willis and Pace Picnic Islands will remain closed to boaters. They’ve been off limits since the Memorial Day weekend after piles of discarded trash were found there. The city said there will be a zero-tolerance policy for trespassers. Miami Beach is also closing Flagler Monument Island for the holiday for the same reason, starting Thursday. It will reopen Monday.