The cycling of elements within the surface oceans and coastal seas has important effects upon marine productivity, atmospheric chemistry and for life on land. These areas are also thought to play a major role in climate regulation via the uptake and release of climatically active gases, such as carbon dioxide (CO2). However, the roles of these chemical and biological processes, as well as the processes performed by the microbial community, are not well quantified or understood and therefore, the way in which they will respond to global change is a major question for science and society. All of the processes that occur in the ocean will be directly or indirectly affected by ocean acidification; the lowering of seawater pH due to human activities, such as the burning of fossil fuels. Uncertainties remain about how any future changes in pH will impact upon element cycling and how this will affect the goods and services provided by the ocean. Increasing fundamental understanding of the ocean, and the invisible processes taking place within, creates a more informed and evidence based foundation for analysing, predicting and responding to the effects of ocean acidification, climate change and developing sustainable marine management strategies. PML has a long and internationally recognised track record in biogeochemical cycling research, which requires an interdisciplinary approach to study the interface of biology, chemistry and physics. Key research areas: a) air-sea gas exchange; b) oxygenated volatile organic compounds (OVOCs); c) dimethyl sulphide (DMS); d) nitrogen cycling; e) ocean acidification; f) primary production; g) microbes and viruses.