His research involves biogeochemistry of trace elements in natural waters, weathering and other controls on river composition, estuarine chemistry, and global carbon systems. At present, most work in his lab involves trace element studies. However, over the years Dr. Shiller has worked in many different areas of geochemistry ranging from sediment studies to radionuclide studies to studies of the oceanic carbon dioxide system. Dr. Shiller's current research involves trace elements in both rivers and the open ocean. Surprisingly little is known about the concentrations of many dissolved trace elements in natural waters and what processes control those concentrations. His work has examined the mechanisms of seasonal concentration variations in the Mississippi and Yukon Rivers, distributions of trace elements on the Louisiana Shelf, and trace element distributions in the open ocean.