Transparent exopolymer particles (TEP) and coomassie stainable particles (CSP): comparing their origin and behavior using flowcam visualization and imaging

The discovery of transparent gel-like particles, such as polysaccharide-containing TEP and protein-containing CSP has changed our conception of particle-organism interaction and raised questions about the origin, composition, and role of gel particles in aquatic systems. Using standard staining methods and a new FlowCAM 3D visualization and imaging technique, we studied whether TEP and CSP are sub-units of the same particle, are distinct particles with different characteristics and behaviors, or both. In a mesocosm, phytoplankton produced both TEP and CSP; however, maximum abundances occured at different phases in the bloom. In the Sargasso Sea, depth profiles of TEP and CSP were different; both were most abundant in the upper 100 m, but CSP followed fluorescence and total particle concentration while TEP decreased with depth. Visual examination using FlowCAM of stained and unstained TEP and CSP from seawater, freshwater, and algal cultures, showed that TEP and CSP have different shapes, sizes and particle-association behaviors. We conclude that TEP and CSP are distinct particles, produced by different species at different growth phases, and their significance to aggregation changes depending on the community composition