Characterisation of fine particles by flow cytometry in estuarine and coastal Arctic waters

The chemical and biological nature of suspended pico- (<2 μm) and nano- (2–10 μm) particles was studied by flow cytometry in the Lena River delta and Laptev Sea, Russia, during September 1991. Forward and wide-angle light scatter, natural fluorescence of phytoplankton, and induced fluorescence of organic molecules were used to characterise natural suspended particles. Organic and inorganic particles were identified by staining with specific fluorochromes: FITC for proteins, Con A-FITC for glucose/mannose, and PNA for galactose. Living and nonliving organic particles were distinguished by analysing simultaneously natural red fluorescence (chlorophyll) and organic staining. The upper Lena River and its delta were characterised by a high concentration of total particles (18.5±4.9×105 per cm3), mostly inorganic (13.6±5.4×105 per cm3). In the coastal and open waters of the Laptev Sea, organic particles dominated. Generally, the most important fraction of small organic particles were nonliving (organic detritus, TEP, and organic coatings) characterised by the presence of proteins and polysaccharides. The phytoplanktonic cells were characterised by a high fraction of picoplankton (1000–50 000 cells per cm3) dominated by Synechococcus sp. and small picoeukaryotes.