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Diatoms are major contributors to global carbon fixation and constitute a significant portion of biofilms found in lotic ecosystems. Despite their widespread abundance and the fact that extensive studies have been performed on morphological features of frustules, molecular tools for the identification of diatoms are not commonly available. This study focuses on the development of oligonucleotide probes for the detection of diatom species relevant to water quality assessment. The selected panel of diatoms covers all the species found in water of varying quality from the rivers of central-East Apennine (Italy). Small subunit rRNA-targeted probes were applied to a microarray platform as well as to a new technique termed Primer-Probe, with the aim of obtaining a molecular tool suitable for accurate identification of both single and mixed species diatom populations. The Primer-Probe technique together with dot-blot assays proved to be ideal for the preliminary screening of a large set of DNA oligonucleotides designed by ARB software. It was shown that microarrays, as a promising technology for rapid and simultaneous detection of a wide range of species-specific genetic markers, can be adapted to monitor changes within a diatom community. It is suggested that microarrays will provide a molecular basis for microbial identification to support standard microscopy techniques used by ecologists and environmental scientists for monitoring water quality. [ABSTRACT FROM AUTHOR]

Physical constrains such as water discharge, suspended solids and turbidity act as dominant factors in driving the planktonic diatom assemblages of the River Adige (North-Eastern Italy). Two sampling stations, characterised by different hydromorphological features (Cortina all’Adige and Boara Pisani, with torrential and more potamal characteristics, respectively) were sampled fortnightly following an integrated approach encompassing physical, chemical and biological measurements and aiming at identifying the dominant factors controlling the temporal development of the community. A morpho-functional approach was used to classify the diatom assemblages where Morpho-Functional Diatom Groups (MFDG) were defined for diatom genera, according to their morphology, habitat selection and modality of adhesion to river substrate. In the two sampling points, algal growth was never limited by nutrients or zooplankton. The irregular development of MFDG was determined by the stochastic hydrological events and changes in variables related to water discharge (suspended solids and light attenuation). Tychoplanktonic, benthic and drifted taxa (such as Diatoma spp., Encyonema spp., Navicula spp. and Nitzschia spp.) were dominant in the torrential station (Cortina all’Adige), while the contribution of euplanktonic unicellular centric taxa (such as Cyclotella spp., and Stephanodiscus spp.) was higher in the potamal station (Boara Pisani). [ABSTRACT FROM AUTHOR]