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Surface Active Particles in a Phytoplankton Bloom

Present state of knowledge of abiotic particles produced during phytoplankton bloom experiments as well as in the upper ocean is mostly based on information gathered by staining techniques [1]. The most frequently followed microparticle class are transparent exopolymeric particles stainable by alcian blue (TEP). TEPs are described as gel particles in the size range from 3-5 &micro ; m to 100 &micro ; m [2]. Particles retained on filters are stained with alcian blue (cationic dye that stains anionic polysaccharides) at pH 2.5. Such procedure may produce structural artifacts including aggregation and rearrangements. In order to gain information on native structure of particles it is essential to develop methods and techniques with potential to analyze particles in their natural aquatic environment without separation (filtration, centrifugation) and to avoid drying process. The Adriatic Sea is mainly phosphorus (P) limited [3], and this was the basis of the design of mesocosm bloom experiment "Rovinj 2003" [4] to follow the dynamics of particle formation. We used a low (1 &micro ; M) and a high (6.3 &micro ; M) P addition, to attempt to achieve two different levels of biomass accumulation. At the same time, this was the unique opportunity to evaluate relation and relevance of presently available measurement techniques for monitoring marine particles. A more specific goal was to contrast particle formation in low P and high P nutrient enrichments using the advantages offered by electrochemical approach. [1] Passow U 2002 Progress in Oceanography 55: 287-333 and references therein. [2] Alldredge A L, Passow U, Logan B E 1993 Deep Sea Research Part I 40: 1131-1140. [3] Degobbis D 1990 Marine Chem 29: 235-25. [4] Žutić V, Svetličić V, Radić T, Malfatti F, Degobbis D, Azam F 2004 Periodicum biologorum 106: 1-6.

electrochemical detection of surface active particles; static mercury electrode; mesocosm experiment; phytoplankton bloom; northern Adriatic Sea

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