FIESTA

The ocean is constantly stirred by currents that swirl and mix seawater creating fronts, filaments and eddies. These dynamic structures are known as ‘fine scales’, and feature spatiotemporal scales of 1-100 km and days-weeks. Fine scales alter biogeochemical gradients affecting phytoplankton productivity and carbon export, but their role in nitrogen cycling is unknown. The greatest source of bioavailable nitrogen in the ocean is nitrogen fixation performed by microbes called ‘diazotrophs’. Understanding the role of fine scales on diazotroph activity and distribution requires dynamic sampling approaches at high-resolution. FIESTA will implement parallel measurements of nitrogen fixation rates, diazotroph abundance and diversity at an unprecedented resolution, >50 times higher than current measurements. This will allow more accurate quantification of nitrogen inputs to the dynamic ocean, which is key to constrain its current and future role in CO2 withdrawal and climate change.