Marine biogeochemistry focuses on the role of the marine system in the global cycles of climatically active trace gases, including sulphur gases, nitrous oxide and methane, parameterisation of air-sea gas exchange and the understanding of large scale oceanographic processes through the use of purposefully released tracers, the role of the bacterioneuston in air-sea trace gas exchange and the reactivity and photochemistry of chromophoric dissolved organic matter in freshwater and marine environments and implications for global biogeochemistry.