New approaches to assess the responses of phytoplankton to global change (PHYTOCHANGE)

The project investigated physiological reactions of 3 important phytoplankton groups (diatoms, coccolithophores, cyanobacteria) to environmental factors which are affected by global change (pCO2/pH, light, nutrients). Using an innovative combination of cutting-edge mass-spectrometric and fluorometric techniques, a suite of in vivo assays were applied in lab and field experiments to develop a process-based understanding of cellular responses. Specific biogeochemical issues were addressed since diatoms are the main drivers of vertical organic C fluxes, coccolithophores regulate ocean alkalinity through calcification, and N2-fixing cyanobacteria control availability of reactive N. These are relevant in different marine zones, from Southern Ocean to equatorial oligotrophic waters. Data has significantly improved understanding of key processes in phytoplankton and was exploited in multidisciplinary contexts ranging from molecular to ecological processes and, through cellular and ecosystem models, to predictions of marine biosphere responses to future global change.