Researchers are combing the coast of several New England states in search of non-native species that pose a threat to public health, shellfish and structures like docks and piers. The one-day sweep in New Hampshire on Monday is part of a six-day effort to collect and catalog marine organisms from Maine’s mid-coast to Cape Cod and Rhode Island. UNH zoology professor Larry Harris says without such a survey, researchers wouldn’t have been able to identify a type of red alga that is fouling beaches and causing problems for the tourism industry. The project is organized by Massachusetts Office of Coastal Zone Management and the Massachusetts Institute of Technology Sea Grant. New Hampshire’s team will start at the UNH Coastal Marine Lab in New Castle before traveling to Hampton.