engleski

Influence of Microphytoplankton Composition on TEP Formation

Phytoplankton excretes diverse polymers into the surrounding medium, both in typical and stressed conditions, with polysaccharides as the largest fraction. By aggregation of acidic polysaccharidic polymers micrometer Transparent Exopolymer Particles (TEP) may be formed, which are exceptionally important in aggregation processes in seawater. Numerous experiments have shown that phytoplankton is the most important source of excreted polymers required for TEP formation although comprehensive studies of the relationship between TEP and phytoplankton in real ecosystems are rare, without almost any attempt at interpreting the role of species composition in TEP formation. Considering statistically significant correlations between TEP and phytoplankton biomass found in the northern Adriatic, additional analysis of the interaction of microphytoplankton composition and TEP along the Rovinj-Po river delta profile during a five-year period was carried out. The aim was to establish whether there exist species which are more important for TEP formation than others, due to differing capabilities of excreting TEP precursors. Results for the ten most often blooming species are shown, of which Skeletonema costatum, Chaetoceros sp. and Pseudonitzschia delicatissima are usually most related to high TEP concentrations. While none of these species causes intensive TEP formation during each bloom, Skeletonema costatum however induces TEP formation more often than other species. It is interesting that Chaetoceros sp. cells were mainly solitary, indicating the different physiological potential of solitary and chain cells of this genus for excreting organic matter suitable for TEP formation. Furthermore, among analysed species, Cylindrotheca closterium, Asterionellopsis glacialis, Pseudonitzschia seriata and Nitzschia longissima f. tenuirostris were those least correlated with TEP formation.

TEP; Microphytoplankton; Northern Adriatic

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