CO2 fixation of dominant bacterial and eukaryotic groups for cruise AMT20 (JC053)

This dataset consists of 100 measurements of group-specific carbon fixation collected during the Atlantic Meridional Transect programme cruise 20 (AMT20, JC053) between 14th October and 21st November 2010. The cruise track between UK and Chile passed through both North and South Atlantic gyres. Pre-dawn seawater samples were collected from 20 m depth and occasionally a second depth at the bottom of the thermocline in 20 L Niskin bottles attached to a standard conductivity-temperature-depth profiler. Seawater samples were spiked with trace metal-clean ¹⁴C radiolabelled sodium bicarbonate (DHI, Denmark). Samples were then incubated at ambient temperatures in a 6 L water tank illuminated by a warm white light-emitting diode array adjusted to a constant output of 500 µmol photons m^-2 s^-1 for 10h. Subsequently, different phytoplankton populations (namely <i>Prochlorococcus</i> and <i>Synechococcus</i> cyanobacteria as well as small (approx. 2&amp;micron;m) and large (approx. 3.1&amp;micron;m) plastidic protists) were sorted according to light-scattering properties (90° or side light scatter, SSC), relative concentration of SYBR Green I stain per particle (green fluorescence; FL1, 530 ± 30 nm), phycoerythrin-content (orange fluorescence; FL2, 580 ± 30 nm) and chlorophyll content (red fluorescence; FL3, &gt;650 nm) using a FACSort instrument (Becton Dickinson, UK). Radio-assaying of samples was carried out using an ultra-low-level liquid scintillation counter (1220 Quantulus, Wallac).