A submersible imaging-in-flow instrument to monitor nano- and microplankton

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The proposed work builds on the "FlowCytobot", a submersible flow cytometer developed by the PIs to observe phytoplankton and microzooplankton in the size range 10-100 m. This gap contains phytoplankton (including many diatoms and dinoflagellates) that can bloom in coastal waters, and microzooplanton such as protozoa that are critical to the diets of copepods and larval fish, so it is important that we monitor the organisms in this size range. The goal of this proposal, is to complete development and testing of a submersible imaging flow cytometer designed to characterize these large phytoplankton and microzooplanktonic organisms. The new instrument is a modified version of FlowCytobot that uses a combination of flow cytometric and video technology to capture high resolution (1 m) images of organisms for identification and to measure chlorophyll fluorescence associated with each image. Images will be classified by software based on a support vector machine approach, while the measurements of chlorophyll fluorescence will allow us to discriminate heterotrophic from phototrophic cells in taxa (such as dinoflagellates) that contain both kinds of members. Quantification of chlorophyll fluorescence in large phytoplankton cells will also enable patterns in bulk chlorophyll data to be better interpreted.Construction of a working version of Imaging FlowCytobot is nearly completed. The new instrument retains the anti-fouling and performance-monitoring capabilities of the original FlowCytobot; it operates autonomously but is remotely programmable and samples continuously; data will be transferred via Ethernet and fiber optic cables to a remote computer for analysis. The next steps in development involve field testing at WHOI and MVCO, optimizing the instrument on the basis of results from this testing, and refining the analysis and control software.