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Phytoplankton abundance and seasonality in the northeastern Adriatic Sea were directly related to the annual regime of the Po River discharge in the period , there was a shift in the timing of the annual Po River maximum discharge and of phytoplankton maxima from spring to autumn. In addition, the eastern coastal area was greatly influenced by oligotrophic karstic rivers and the Eastern Adriatic Current. Dominant phytoplankton taxa were defined on the basis of abundance and frequency of appearance. Such an approach may help in the comparison of phytoplankton communities within different environments. The dominant taxa were the diatoms Cerataulina pelagica, Chaetoceros socialis, Chaetoceros vixvisibilis and Pseudo-nitzschia spp., which appeared at maximum abundances )10 6 cells l -1 in more than 20% of samples. Among other phytoplankton, the most common was the coccolithophorid Emiliania huxleyi (maximum abundance of 2=10 5 cells l -1 in 50% of samples), and the dinoflagellate Prorocentrum minimum (maximum abundance of 3=10 5 cells l -1 in 12% of samples). The present state of the phytoplankton community may provide valuable information for evaluation of possible future environmental changes in the shallow Mediterranean ecosystem.

Summary:During the June 2010 survey of phytoplankton and physicochemical parameters in the Krka River estuary (eastern Adriatic Sea), a cryptophyte bloom was observed. High abundance of cryptophytes (maximum 7.9×10 6 cells l -1 ) and high concentrations of the class-specific biomarker pigment alloxanthine (maximum 2312 ng l -1 ) were detected in the surface layer and at the halocline in the lower reach of the estuary. Taxonomical analysis revealed that the blooming species was Plagioselmis cf. prolonga. Analysis of the environmental parameters in the estuary suggested that the bloom was supported by the slower river flow as well as the increased orthophosphate and ammonium concentrations. The first record of a cryptophyte bloom in the Krka River estuary may indicate that large-scale changes are taking place in the phytoplankton community. Such changes could have a major impact on the natural ecosystem dynamics and the mariculture production in the area.Keywords: estuarine ecosystem; phytoplankton bloom; cryptophytes; chemotaxonomy; Mediterranean Sea; Krka River estuary.Proliferación de una criptófita en un estuario mediterráneo: alta abundancia de Plagioselmis cf. prolonga en el estuario del río Krka (Adriático) Resumen: Se observó una proliferación de una criptófita durante el estudio del fitoplancton y de los parámetros fisicoquími-cos en el estuario del río Krka (Adriático) en junio de 2010. La abundancia más alta de criptofitas (máximo 7.9×10 6 células l -1 ) y las mayores concentraciones del pigmento marcador específico de la clase, la aloxantina (máximo 2312 ng l -1 ), fueron detectados en la capa superficial y en la haloclina en el tramo inferior de la ría. El análisis taxonómico reveló que la especie que proliferó fue Plagioselmis cf. prolonga. El análisis de los parámetros ambientales del estuario sugirió que la proliferación estaba favorecida por el caudal lento del río, así como el aumento de las concentraciones de ortofosfato y amonio. El hecho de registrar por primera vez una proliferación de una criptófita en el estuario del río Krka podría indicar cambios a gran escala en la comunidad de fitoplancton. Tales cambios podrían tener un impacto importante en la dinámica de los ecosistemas naturales y la producción de la maricultura en la zona.Palabras clave: estuario; proliferación de fitoplancton; criptófitas; quimiotaxonomía; mar Mediterráneo; estuario del río Krka.Citation/Como citar este artículo: Šupraha L., Bosak S.,

The diatom genus Proschkinia is a common element of biofilms covering diverse substrata in saline inland or shallow coastal environments. It can be distinguished from other naviculoid taxa by its lanceolate valves with a fistula located within the central area and numerous open girdle bands with a U-shaped cross-section and a single row of perforations on the internal side of the fold. Despite this distinct morphology, frustules of Proschkinia are typically weakly silicified and often overlooked when cleaned diatom material is analysed. The current paper describes six new species of Proschkinia: P. browderiana sp. nov., P. lacrimula sp. nov., P. maluszekiana sp. nov., P. sulcata sp. nov., P. torquata sp. nov. and P. vergostriata sp. nov., found in numerous samples of marine organisms, such as sea turtles (including sea turtle museum specimens), sea turtle-associated barnacles and seagrass from across the three oceans. Some of the newly described taxa were found on multiple individuals belonging to different sea turtle species, whereas others were in samples collected from different continents. Molecular phylogenetic analysis indicated that examined Proschkinia strains formed a monophyletic clade, sister to Fistulifera.