Coupling autofluorescence imaging of freshwater samples containing cyanobacteria with R-MHD microfluidic pumping toward investigation of harmful algal blooms.

by Rathke, Nicholas; Boyd, Erin E.; Muldoon, Timothy; Fritsch, Ingrid

Redox-MHDs (R-MHD) microfluidic pumping is a convenient method for facilitating the flow of a variety of electrolyte-contg. fluids. It requires a magnetic field and two electrodes modified by a conducting polymer such as poly(3,4-ethylenedioxythiophene) (PEDOT). The MHD force allows for a high degree of control over the speed and direction of the fluid for a variety of applications. One problem that will be addressed is the use of R-MHD in imaging, identification, and enumeration of the various cyanobacterial species responsible for harmful algal blooms (HABs). HABs arise from factors such as eutrophication of water bodies, elevated temps., and intense sunlight that can result in dramatic increases in local cyanobacterial populations. This is problematic, as several species of cyanobacteria are known to release toxins into the water system, and the concns. of these toxins can reach dangerous levels during an HAB. This creates several issues, as the afflicted water can no longer be used as a source of drinking water, for recreation, and any fish from that area could be unsafe to eat. This work aims to accomplish two goals, the first of which is to demonstrate that despite the relatively low electrolyte concn. in freshwater (aprox. <4 mM NaCl), R-MHD is capable of producing sufficient flow speeds and a well-defined flow profile for quantification of cyanobacteria. Addnl., it establishes configurations with which R-MHD platform can be interfaced with a fluorescence microscope and camera that take advantage of the autofluorescing chlorophyll and phycocyanin found in abundance in cyanobacteria to collect high resoln. images of the cyanobacteria responsible for the HAB, in a compact, easily transported unit. This information can be used to create a distributed sensing network that could function as an early warning system for HABs.