Erik Björn, Umeå University (IMAGE) Umea University Caption Erik Björn is injecting small amounts of isotopically enriched mercury to the sediments for the mesocosm experiment. By adding stable (not radioactive) isotopes of mercury the scientists could trace how methylmercury was formed and accumulated in plankton in the mesocosm systems. Credit Sofi Jonsson Usage Restrictions This photo may only be used in contexts related to this news release. Please give credit to the photographer. 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.