Cruise: Gradients 2, MGL1704 Project Name: Simons Foundation, Gradient NPSG Dataset Description: The Imaging FlowCytoBot (IFCB) is an in situ automated imaging flow cytometer that generates images of particles suspended in seawater, in this case from the underway uncontaminated seawater system aboard the R/V Langseth (intake 5m). The IFCB uses a recycled sheath fluid (0.2 µm filtered seawater) to align and drive particles individually towards a light source (red laser, 4.5 mW) in order to detect and identify single or colonial cells using a combination of optical properties (red fluorescence and light scattering intensities) and high resolution images (3.2 pixels per micron) by a mounted camera. Both optical properties are used to trigger targeted image acquisition of suspended particles in the size range <4 to 100 μm. The instrument continuously samples (few seconds) from ~5 ml aliquots from the intake, and processes all particles contained in that volume for the next 20 mins. Images corresponding to the "Sample" variable are available on the cruise's dashboard (http://ifcb-data.soest.hawaii.edu/IFCB_NPTZ). This dataset is for the abundance of imaged cells by genus. For each sample, the total number of cells classified to the genus-level by a random forest algorithm (Sosik and Olson, 2007 doi:10.4319/lom.2007.5.204) is counted and divided by the corresponding volume analyzed (~5 mL). Note that we used all the images collected during Gradients 2.0 to train the random forest algorithm and that classification is therefore highly accurate for this dataset. Using 7 µm calibration beads, we estimated that the error of cell concentration due to cell detection during sample acquisition averages 11 ± 10 %, independently of concentrations in the range 1-10000 cell/mL.