Electrospray ionization-quadrupole ion trap mass spectrometry (ESI-QITMS), either in positive- or in negative-ion mode, has been used to establish the chemical structures (chain length, degree of unsaturation, positional distribution) of the fatty acids attached to the primary (sn-1) and secondary (sn-2) hydroxyl groups of the glycerol moiety of natural monogalactosyl- (MGDG) and digalactosyldiacylglycerols (DGDG), isolated from the freshwater dinoflagellate Glenodinium sanguineum and from a marine diatom belonging to the genus Chaetoceros. Fragmentation by collision-induced dissociation of a single component in MGDG and DGDG mixtures, separated by high-performance liquid chromatography (HPLC) and detected on-line by tandem positive-ion ESI-MS, leads to a clear-cut determination of the positional distribution of the sn-glycerol-bound fatty acyl chains. Reversed-phase liquid chromatography allowed a partial resolution of the component mixture before ESI-MS/MS analysis. These results were validated by comparison with ESI-MS data obtained for the sn-2 lysoglyceroglycolipids synthesized via regiospecific enzymatic hydrolysis of the corresponding diacylglycerols by Rhizopus arrhizus lipase.

The depth-distribution of epilithic diatoms in a carbonate meromictic lake (south-eastern Alps), characterized by marked water-level fluctuations, was investigated. Fixed stations were placed along a depth-profile at intervals of 2-3 m and sampled throughout the year using scuba diving. Diatom analysis included quantification of living cells (biovolume calculations) and the estimation of fucoxanthin concentration, which, coupled with the analysis of digested material, permitted taxonomic determination at specific or subspecific level. Multivariate analyses indicated the following variables to be significant: water-level fluctuations, photosynthetically active radiation, silica and nitrates. Diatoms had distinct depth-distributions. Quantification of densities, biovolumes and Chl a, and physiological (senescence index, fucoxanthin), functional (photosynthetic efficiency), and community structure (diversity) parameters allowed the definition of three depth-distribution zones (shallow, mid-depth and deep). The different diatom communities in these zones were confirmed by ANOSIM (analysis of similarity). The shallow, mid-depth, and deep zone were characterized by disturbance due to water-level fluctuations, high stability with favourable growth conditions and severe light limitation, respectively. Community composition and diversity depth-distribution features remained relatively stable throughout the year, while marked changes in benthic diatom biovolumes were modulated by competition for light with phytoplankton. Fucoxanthin was strongly correlated with epilithic diatom biovolumes. The results indicate that depth-distribution patterns should be considered when performing lake diatom biodiversity inventories and integrity evaluations because water-level fluctuations are likely to increase in many lakes due to increased withdrawal of water and climate change in the future.

Ochrobactrum anthropi is a gram-negative bacillus recognized as a human opportunist pathogen isolated in clinical specimens and not of clinical significance. We report a new aspect of this bacterium, that it has been isolated from activated sludge. In fact, it is able to grow on atrazine (2-chloro-4-ethylamino-6-isopropyl-amines-triazine) by utilizing it as the only source of carbon. Our results show that atrazine (0.03 g/liter) causes a dramatical increase in the degree of saturation of membrane fatty acids. Analysis and identification of bacterial fatty acids were performed by gas chromatography and gas chromatography-mass spectrometry techniques.

In Lake Tovel, an oligotrophic and weakly stratified lake, the dinoflagellate Borghiella dodgei Moestrup, Hansen et Daugbjerg, showed a peculiar spatial-temporal pattern with highest abundances in the bottom of the shallow side bay (4 m) along with remarkable abundance variations fromyear to year. We investigated B. dodgei's growth in laboratory cultures and related results to their implication for bloom formation. B. dodgei was cultivated under different temperature, nutrient and light conditions. Growth rates, cell biovolume, cyst formation and pigment and mycosporine-like amino acids (MAAs) concentrations were determined. Experiments showed that this alga (i) had higher growth rates at low temperatures (\7°C) and high irradiance levels (*250 lmol m -2 s -1 ), (ii) produced higher yields with organic supplements such as peptone, (iii) did not grow in the dark even with organic supplements, (iv) survived for long periods without a light source, (v) synthesised MAAs, (vi) showed an increase in cell volume with nutrient shortage and increasing temperatures ([7°C) and (vii) had high encystment rates with temperatures [7°C. These laboratory fingerprints allowed us to construct a theoretical model defining the species' niche. Borghiella needed a mixture of low temperatures, high irradiance levels and sufficient quantities of dissolved organic nitrogen to form blooms. Such a strict combination was probably a transient situation and occurred in oligotrophic Lake Tovel only in early summers followed by heavy spring rains.

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