engleski

From microparticles to giant gels of Northern Adriatic

Abiotic transformation of organic matter in the aquatic environments such as seawater depends more on the interfacial properties of organic matter than on its chemical composition. These properties, purely understood so far, can be measured by a direct application of the electrochemical adhesion sensor which we have developed based on our fundamental studies in the fields of surface electrochemistry and biophysics. Newly postulated biophysical processes of biopolymer selforganization into microparticles and mechanism of sol-gel phase transitions are held responsible for transformation of dissolved biopolymers and microparticles to macroscopic phases. The macroscopic gel phase appears, episodically in Northern Adriatic, as large aggregates within the water column or covering tens of square kilometers of sea surface. Current views leave no doubt on phytoplankton production and bacterial transformation of polysaccharides as main constituents of the gel matrix. The phenomenon has so far been specific for Northern Adriatic but with the global climatic changes and increasing nutrient load it could be anticipated to spread over other coastal seas of Mediterranean. There is by now accumulated evidence ranging from satellite observations to microbiological studies on sudden and dramatic changes of dispersed state (microparticles) to macroscopic gel-phase. We introduce a simple electrochemical technique to detect microparticle precursors and to follow the transition to the gel phase. When micrparticles attain critical concentration Nc (our present estimate centers around Nc  5x107 L-1) the large-scale phase transition from the dispersed to gel state takes place. AFM is introduced to image 3-D structure of the gel matrix and biopolymer molecules.

microparticles; marine gel; self-organization of marine biopolymers

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