Abundance and characteristics of polysaccharide and proteinaceous particles in Lake Kinneret

Two kinds of hitherto undetected transparent particles were studied in Lake Kinneret, Israel. By using the dyes Alcian blue and Coomassie blue we visualized particles with polysaccharide (transparent exopolymer particles [TEP]) or protein components (Coomassie blue stained particles [CSP]), respectively. A large proportion of TEP and CSP in this lake appeared to be derived from previously particulate, detrital material. Combining microscopic observation with image analysis, we quantified particle abundance, projected spherical encased volume (PSEV) and surface area (SA). Although highly variable in abundance and characteristics, both kinds of particles were ubiquitously present throughout the year. TEP abundance ranged from 4.4 x 10(2) to 2.5 x 10(4) particles ml(-1), with concentrations of PSEV from 80 to 5503 mm(3) l(-1) and SA from 897 to 15 073 mm(2) l(-1). CSP abundance varied from 1.4 x 10(2) to 1.2 x 10(4) particles ml(-1), with concentrations of PSEV from 8 to 5199 mm(3) l(-1) and SA from 200 to 14 514 mm(2) l(-1). CSP were generally about 3-fold fewer in abundance than TEP but the average PSEV and SA of CSP were usually greater than those of TEP. In contrast to TEP, significant linear correlations were found between CSP parameters (abundance, PSEV and SA concentrations) and either chlorophyll concentration or phytoplankton biomass measured at the same date. Higher densities (similar to3- to 10-fold) of attached bacteria were observed on CSP than on TER The PSEV concentrations of TEP and CSP in the lake water were much greater than the volume of ambient phytoplankton. Transparent particles may be important in a variety of ecosystem processes: in the formation of macroaggregates (lake snow), in the sedimentation or horizontal advection of materials, as specialized environments for microbial function leading to nutrient recyling, as a particulate food for micrograzers, and as sites for adsorption of trace metals. The high concentrations of TEP and CSP found in Lake Kinneret suggest that these particles together with their associated microflora play a critical and dynamic role in this lake ecosystem.