An Imaging Flow CytoBot (IFCB) is a rugged and waterproof flow cytometer which additionally captures high resolution images (~3.4 pixels/micron) of individual particles that pass through its fluidics. IFCBs are designed for long-term unattended deployments to monitor the phytoplankton community composition. To prevent fouling, the IFCB is equipped with biocides to flush the sheath fluid and sample tubing daily. The IFCB works by drawing in 5 milliliters of water, and all particles in that parcel of water are hydrodynamically focused to pass through a flow cell in single file. These cells are then exposed to a pulse of light that causes pigmented cells (e.g. chlorophyll) to fluoresce, which enables us to separate phytoplankton from non-pigmented cells. Phytoplankton cells are counted and high-resolution images are captured and stored using microsecond flash lamp pulses.
PhytoChop houses an autonomous nutrient sampler ‘NuLab’ from Green Eyes Environmental Observing Systems. This unit consists of three measuring chambers that measure ammonium, nitrate/nitrite, and soluble reactive phosphate. The NuLab performs online colorimetric wet chemistry assays using standard methods. The round dials shown in the photo are connected to a variety of reagents, standards, waste, and sample inlets. Not shown in this picture is a small Rasberry Pi microcomputer that reads in the data and stores it in the cloud. The NuLab is currently programmed to sample every 2 hours.
The LabSTAF is is a 4th generation active fluorometer from Chelsea Technologies that is used to measure the biomass and photosynthetic rates of the phytoplankton community. This specific instrument possesses seven excitation wavelengths (centered at 452, 471, 505, 517, 534, 594, and 624 nm) that provide an independent assessment of the photosynthetic physiology and biomass of different pigment groups, for example phycocyanin-rich cyanobacteria that are excited by yellow light (594 nm), versus peridinin-rich dinoflagellates that are excited by blue light (490 nm). Alongside the IFCB that gives us a good metric of what is in the water, this instrument provides an additional measurement of biomass and diversity, and critically yields important metrics of phytoplankton metabolism.