Two more great white sharks have been tagged off Chatham Harbor, prompting the closing of Lighthouse Beach and several other beaches, the Chatham harbormaster said Thursday. Personnel from the Division of Marine Fisheries used harpoon-tagging technique to tag the sharks from their fishing vessel Thursday. They tagged one 18-foot-shark in the morning and a 16-foot shark in the afternoon, said Greg Skomal, the state’s shark specialist. In addition to Lighthouse Beach, all eastern-facing ocean beaches remain closed from the Orleans-Chatham line to Nauset Beach until further notice. All other public beaches remain open to swimming. Swimmers are encouraged to be aware of their surroundings and not swim within 300 feet of seals and report any shark sightings to the harbormaster’s office, at 508-945-5185. On Aug. 31, two great white sharks, roughly 14 and 16 feet in length, were tagged 100 yards off Orleans. There have been 15 sharks tagged so far this season, Skomal said.