One key to a better understanding of the biology, optics and geochemistry of the oceans is more detailed knowledge of the composition and characteristics of the suspended particles.  At present, analysis of microscopic particles requires bottle sampling from a ship, which limits the resolution and duration of many studies.  We propose to develop an instrument to analyze the optical properties (light scattering and fluorescence) of individual microscopic particles in situ and unattended, using established techniques of flow cytometry; the instrument will be designed for eventual moored operation.  Developments allowing this instrument to now be practical include low-power-consumption solid state lasers providing enough power to allow fluorescence measurements of single phytoplankton cells, and artificial neural network systems to cope with the large amounts of data from multiparameter analyses of individual particles.  To increase reliability, we propose to use a simple ducted flow to replace the mechanically complex hydrodynamic sample stream focussing of conventional flow cytometers.  To use this simple flow system will require that we be able to recognize and reject signals from particles passing through the edges of the excitation spot; this can be achieved by measuring light scattering from two orthogonal beams (from IR diode lasers) which define the sensing region.

Funds provided by NSF grants OCE-9416551 and 9907002, DOE grant DE-FG02-95-ER61982, and ONR grant N00014-93-1-1171.
 

Figures from the poster presentation at the 1999 ASLO Meeting in Santa Fe, NM