engleski

Electrochemical evidence of muco-polysaccharides formation: The role of anoxic microzones

The appearance of mucilages in the Adriatic as well as more frequently in other coastal waters around Europe are basis of many laboratory and field studies with the aim of finding out the origin and causes of this phenomenon. A novel definition consider mucilage aggregate like an anomalous accumulation of organic matter produced by several marine organisms depending on the peculiar climatic conditions which are known to support the mucilage formation1. Namely, conditions such as hot springs and summers, following mild winters with reduced rates of marine current and wave motion resulting in anoxic conditions along the water column was observed during the last appearance of the mucilages in the Adriatic Sea2. In the field studies diatoms are found to be the major producers of mucilagionus material. Diatoms are known to produce copius amounts of colloidal mucus and other exopolymeric material3. This colloidal mucus by processes of aggregation, coagulation and flocculation are transfering from particle size to form microaggregate which may grow futher and under particular conditions lead to various structers of macroaggregates (macroflakes, strings, clouds, gelatins). The basis of this study is hypothesis of possible very important role of sulfur species in the formation and stability of mucus aggregates in the Adriatic Sea4. We have investigated the influence of anoxic conditions on the muco-polysaharides transformation in already formed phytoplankton aggregates of benthic diatoms. The samples were incubated in the time period of 1 month with 10-4 and 10-3 M concentrations of sulfide. In the same samples by using electrochemical methods interaction between sulfide and molecule of polysacharides as well as formation of high molecular sulfopolysacharides have been observed in relatively short time (10 days) and at room temperature. Interaction of sulfide and organic matter become also visible through change in a physico-chemical properties of present organic matter by following changes in surfactant activity. Concentration of surface active substances (SAS, eq. to conc. of Triton-X-100) in untreated sample was 0.35 mg/L in aggregate and 0.59 mg/L in ambiental water while in sample treated with sulfide SAS have been increased several times, up to 20 mg/L. In the ambiental water of the same treated samples huge increase in concentration of DOC have been recorded (from 7.17 mg/L in untreated and up to 40 mg/L in sulfide treated samples). Observed results are in agreement with hypothesis which predict that mucus material in the seawater originated not only from cell secretion but also from intracellular carbon storage material from lysed cells5. The major idea is that intracellular particulate polysaccharides when released from cells after interaction with sulfide could wind up in layers and filaments to form gel-like compounds. References 1. M.Mecozzi, R.Acquistucci, V.Di Nato, E.Pietrantonio, M.Amici, D.Cardavilli, Chemosphere 44 (2001) 709. 2. D.Degobbis, R.Precali, I.Ivančić, N.Smodlaka, D.Fuks, S.Kvedar, Int.J.Environ.Pollut., 13 (2000) 495. 3. T.Kiorbe, J.L.S. Hansen, J.Plankton Res., 8 (1993) 475. 4. I.Ciglenečki, B.Ćosović, V.Vojvodić, M.Plavšić, K.Furić, A.Minacci, F.Baldi, Mar.Chem. 71 (2000) 233 5. F.Baldi, A. Minacci, A.Saliot, L.Mejanelle, P.Mozetić, V.Turk, A.Malej, Mar.Ecol.Prog.Sci., 153 (1997) 45.

voltammetry; reduced sulfur species; mucilage formation; benthic diatoms; Adriatic Sea

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