Dr. Reinfelder’s research addresses the biogeochemical cycling of major and trace elements in marine and terrestrial aquatic ecosystems including the accumulation, limitation, and trophic transfer of elements in aquatic food webs, cycling and air-sea and land-air exchange of mercury in terrestrial, estuarine, and oceanic waters, subsurface biogeochemistry of sulfur-bearing minerals and associated trace elements, and the physiological ecology of carbon assimilation in marine phytoplankton. John teaches a graduate course in aquatic chemistry, an undergraduate course in environmental chemistry, and a freshman seminar on estuaries.