The goal of this program is to fabricate a small, submersible, robust, microflow cytometer uFC for quantitative detection of phytoplankton. In situ detection of phytoplankton is a niche market directed at climate and environmental research. This market is growing. There are more than 200 underwater gliders currently deployed for scientific research. Our uFC will ultimately be a common option on these underwater platforms. In order to achieve significant penetration of this market, the equipment price needs to be reasonable and its operation/deployment simple. We are well positioned to meet these requirements. There are significantly larger research markets for our uFC. For example NOAA has deployed ARGO, a global array of 3,000 free-drifting profiling floats that measure the temperature and salinity of the upper 2000 m of the ocean. These buoys could be equipped with our uFC. Additional units could be deployed onboard seagoing cargo ships to monitor the open ocean. The Navy has interest in better methods of detecting phytoplankton blooms, as they can interfere with submarine navigation or detection, and they are also interested in water quality issues associated with coastal assets. There are major commercial developments to pursue the use algae as a biofuel source. This emerging industry will need a means to monitor algae growth, which could be served by a variant of our uFC. There are also proposed water standards that call for algae monitoring. Scientists employ satellite-based sensors to measure the amount and distribution of chlorophyll a, an indicator of phytoplankton biomass in the ocean. For example NASA's Aqua satellite is monitoring red-light fluorescence emitted by phytoplankton. Red-light fluorescence reveals insights about the physiology of marine plants and the efficiency of photosynthesis, as changes in fluorescence emission reflect the amount of light and nutrients available for growth. The instruments onboard these satellites must be calibrated, and the algorithms applied to the collected raw data need to be validated. Therefore it is important to have sea-based instrumentations to provide an independent verification and confirm the validity of the data collected using spaced-based platforms. These validation instruments are typically deployed on buoys in coastal zones and research vessels out in the open ocean. Current sensors for at-sea applications are expensive, physically large, and have considerable consumable needs. Our proposed low-cost sensor will allow for more extensive deployment of units and allow for more extensive verification and calibration of satellite data, thus enhancing NASA's Earth science research capabilities. It will be extremely robust and capable of operating in an autonomous or semi-autonomous basis for extended periods. In addition, should there be a mission to Europa, this technology may be of use on such a mission under that moon's ice field.