A new study has shown that periphyton -- a community of algae, bacteria, and other natural material living on submerged surfaces -- is helping to transform mercury from a Superfund site into methylmercury, a more toxic form. The study, led by Dartmouth College Superfund Research Program (SRP) researchers, also found lower than anticipated levels of methylmercury in small fish located downstream from a former chemical plant, despite elevated levels of methylmercury in sediment, water, and periphyton.