recreational area, which has raised concern for the lake's water quality. Citizens and local government believe the lake suffers harm from increased loads of nutrients, including phosphorus and nitrogen, from septic systems, fertilizers, and runoff from roads. The most obvious change has been the introduction of zebra mussels. Zebra mussels, which have no known predators in U.S. waters, threaten the existence of native clams and result in more vegetation growing on the bottom of the lake. Residents at Higgins Lake have begun actively lobbying for laws to enforce cleaning of boats before they can be put into the lake, as well as programs to try to combat other foreign pests and intruders to preserve the lake's natural ecology. Gallery See also List of lakes in Michigan References External links Higgins Lake/Roscommon Chamber of Commerce Lakes of Michigan Bodies of water of Roscommon County, Michigan Tourist attractions in Roscommon County, Michigan