Abstract
During the massive mucllage event in the northern Adriatic Sea in July 1991 samples of macroaggregate were fixed in different ways: with formaldehyde, deep frozen and freeze-dried. Conventional microscopy (light and epifluorescence) revealed different autotrophic species embedded in gelatinous matl-ix. Cyanobacteria and heterotrophic bacteria were also identified. Scanning confocal laser microscopy (SCLMI and fluorescent molec~~ la r p obes (the lectins concanavalin A and UEA-I) showed wall-free cytoplasm and particulate polysacchar~des leaklng from the envelopes of broken cells in the matrix. The extensive cell lysis was supported by the observation of cytoplasn1-free cytoskeletons, stained by the molecular probe phalloidin High concentrations of triglycerides (30Y0 of total lipids) and free fatty aclds (22'2%) along with very low concentrations of phospholipids ( 2 % ) also indicated massive cell degradation in freeze-dried material. The mucllage observations were compared with those of a natural plankton community grown under hlgh nutrlent conditions using the same techniques. Free polysaccharides were observed as globular flocs (marine snow) during in situ enrichment experiments and inti-acellular polysaccharides as carbon storage materials In autotrophic organisms. No strings, filaments, layers, cell lysis or lipid classes indicating strong cell biodeterioration were observed in a 1 mo controlled experiment during an algal bloom.
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