Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and the reactions that govern the composition and functioning of the Earth system. We are developing a predictive understanding of human-environment interactions for the future. Part of our research is focused on the human impact of inorganic and organic nutrient inputs to aquatic environments, especially the Baltic Sea. Particular emphasis is placed on the scientific basis of how we should understand the causes of the lack of oxygen in the bottom of the Baltic Sea and how we can best tackle this big problem and solve it as quickly as possible. We use paleoecological techniques and analysis of monitoring data to help understand long-term trends in aquatic ecosystems. In addition, we are making novel connections between the carbon and silicon cycles over the Phanerozoic to join two of Earth’s main biogeochemical cycles through Earth’s history. Within this research theme we are particularly interested in weathering and the linkages between the silica cycle and CO2 concentrations in the atmosphere and the ocean. We are making significant advances in our understanding of the controls of long-term climate variations through the study of interactions between the globally important biogeochemical nutrient (N, P and Si) cycles and the carbon biogeochemical cycle.