An Embedded Cytometer for Autonomous Platforms

University Of Washington, Seattle WA

Investigators

Abstract

The photosynthetic microbes – the phytoplankton – generate about 50% of the oxygen and organic matter produced on Earth each year and serve as the base of marine food webs. Flow cytometers are essential oceanographic instruments that rapidly and accurately measure the abundance, size and fluorescent characteristics of individual phytoplankton cells. For example, flow cytometry led to the discovery of Prochloroccocus, the most abundant photosynthetic organism on Earth. However, thirty-seven years after the first description of a flow cytometer designed specifically for the measurement of phytoplankton in the field, the complexity of flow cytometry, and the multi-parametric data it produces continues to be an obstacle to its evolution towards common use as an oceanographic field instrument. PipeCyte is a miniature, low-power flow cytometer instrument that was designed to perform autonomous measurements of 0.5-10 µm diameter phytoplankton while deployed on autonomous oceanographic measurement platforms. In this first deployment project, the PipeCyte instrument will be immersed at depths of up to 100 meters while tethered to a surface buoy. A surface buoy is a low-cost platform that is simple to deploy from a research vessel. In this project, several buoy deployed PipeCyte instruments will be released in the open ocean to perform measurements of the phytoplankton community at multiple depths. These measurements will provide an unprecedented view of the relation between environmental features and phytoplankton communities along the water column. A previously developed PipeCyte prototype will be iterated to reduce both size and power requirement through a redesign and repackaging of the custom acquisition and control circuitry. This new sub-20 watt PipeCyte V2 will be housed within a commercially available pressure housing. After instrument calibration in the lab using calibration microspheres and cultured phytoplankton, initial field testing of a float-tethered instrument will be performed in the Puget Sound. Automated data analysis methods previously developed in R for analysis of SeaFlow flow cytometer data will be ported to the PipeCyte Labview based control software so that the multi-parameter flow cytometer data can be reduced to phytoplankton population counts in realtime. This reduced data set along with GPS fix will be transmitted back to ship and shore by satellite modem. The proposed buoy-deployed instrument will be powered by four 100 W-hr lithium batteries to yield instrument on-time of approximately 50 hours per deployment. Final field testing to demonstrate proof-of-concept will occur in the sub-tropic Pacific Ocean where real-time counts of Prochlorococcus, Synechococcus and small eukaryotic phytoplankton will be broadcast to the ship. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.