Dartmouth Superfund Mercury Site (IMAGE) Dartmouth College Caption Methylmercury is a highly toxic form of mercury and the form that most easily passes up the food chain where it can reach high concentrations in predator fish. Credit USGS Usage Restrictions Credit USGS License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.