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Blooms of centric diatoms are a common feature in the Bilbao estuary during summer when river flow is at its lowest and water temperature is above 20ºC. To gain insight into the specific composition of these diatom blooms, net samples and cultures of estuarine isolates were analysed under the scanning electron microscope (SEM) and by molecular analyses of the Internal Transcribed Spacers 1 and 2 plus the coding region 5.8S (ITS region) and the 28S rRNA gene. Seven species of solitary centric diatoms belonging to four genera were found in the estuary including: Conticribra weissflogii, Cyclotella atomus var. atomus, Cyclotella cryptica, Cyclotella marina, Cyclotella meneghiniana, Discostella pseudostelligera and Thalassiosira pseudonana. Dominant species during blooms were C. meneghiniana and Co. weissflogii in the upper estuary and D. pseudostelligera and T. pseudonana in the middle estuary. The morphological traits used to differentiate between species pairs of similar morphology (C. meneghiniana/C. cryptica or D. pseudostelligera/D. woltereckii) were observed to vary with environmental conditions, denoting a great deal of phenotypic plasticity which would hinder accurate identification of the species when using morphological approaches alone.

The genus Coolia, which contains potentially toxic epibenthic dinoflagellate species, was studied throughout 17 sampling sites on the Atlantic coast of the Iberian Peninsula during the summers of 2010–2012. Cells from natural samples were isolated into culture, and the strains were observed by light and scanning electron microscopy in order to study and measure the morphological traits. A detailed compilation of previously compiled Coolia measurements was used for comparisons. To gain insight into the taxonomy of the strains, two regions of the nuclear-encoded rDNA were used as markers to infer phylogenetic relationships: the large subunit (LSU) and the internal transcribed spacers ITS1 and ITS2 plus the 5.8S region of the gene (ITS). Two species were found within the study area: Coolia monotis, which was widely distributed throughout the entire area, and Coolia cf. canariensis, which was found at only one sampling site. The observed morphology of the clonal cultures was supported by their accepted taxono...

Individuals of Ostreopsis , a genus containing potentially toxic species which affects human health, were collected during summer-autumn 2010 and 2011 from 17 sites located along the Atlantic coast of the Iberian Peninsula, a temperate area which during summer presents contrasting seawater temperatures. Ostreopsis cells were obtained by shaking macroalgae collected from rocky-shore areas bordering accessible beaches. Isolated strains and field samples were analyzed for morphological and phylogenetic characterization where sequences of the ITS1-5.8S-ITS2 region of the rDNA delineated two different species fitting Ostreopsis cf. ovata and Ostreopsis cf. siamensis . By means of calcofluor staining and scanning electron microscopy, it was observed that field samples of both species exhibited a wide and overlapping range of dorsoventral as well as width values. Those cells presented 11–18 pores/100 μm 2 and were also similar concerning plates shape and size. The main differential feature between the two species was the presence of two sizes of thecal pores (0.07–0.13 μm and 0.15–0.39 μm) in Ostreopsis cf. siamensis and one size (0.24–0.56 μm) in Ostreopsis cf. ovata . A comparison of field vs. cultured cells indicated that field isolates presented larger cells than in culture.

Teleaulax is a genus of delicate cryptophytes that are common and sometimes abundant in marine samples. Previous to this study, only three species (Teleaulax acuta, T. amphioxeia and T. merimbula) were known in the genus. Here, two new species were described from strains isolated from plankton samples collected at the seaward end of the NervioiIbaizabal River estuary (south-eastern Bay of Biscay). They were examined by light microscopy and scanning and transmission electron microscopy, and the nuclear 18S rDNA was sequenced to infer the molecular phylogeny. The species of this genus have been distinguished by size, shape (especially of the cell anterior and posterior), swimming behaviour, morphology of the posterior band and the relative extension of the furrow. The most characteristic traits of Teleaulax gracilis sp. nov. were the cell anterior, that was only slightly rostrate, and the shape of the cell posterior, which tapered off gradually in form of a wedge and finished in a pointed antapex sustained by a V-shaped band. Teleaulax minuta sp. nov., with a length of 5–6.8 lm, is the smallest within the genus and lacks a posterior band. Common features shared with other congeners are, among others, the long furrows, the more or less rostrate cell anteriors and tapered posteriors, a sheet-like internal periplast component thinner than the plasma membrane and the thylakoids arranged in stacks of three.

Ten species of the genus Pseudo-nitzschia were identified in the Nervion River estuary from preserved net tow samples and 31 strains isolated from the estuary. Species identification was performed by means of ultrastructural analysis of valve ornamentation and genetic analysis of selected strains of the P. delicatissima complex. Identified species include: P. australis, P. fraudulenta, P. pungens and P. subpacifica from the P. seriata complex, and P. arenysensis, P. galaxiae, P. multistriata, P. pseudodelicatissima and two uncertain P. pseudodelicatissima-like genotypes from the delicatissima complex. Most clonal strains corresponded to P. pseudodelicatissima-like taxa, P. fraudulenta and P. galaxiae. We were unable to identify the strains of the P. delicatissima-like complex solely on the basis of morphology. A comparison of sequences of the rDNA ribosomal Internal Transcribed Spacers (ITS), including the regions ITS1, 5.8S and ITS2, of four strains of the P. delicatissima complex plus 23 sequences of ta...

17 páginas, 8 figuras, 4 tablas, A single cell of the dinoflagellate genus Fukuyoa was isolated from the island of Formentera (Balearic Islands, west Mediterranean Sea), cultured, and characterized by morphological and molecular methods and toxin analyses. This is the first report of the Gambierdiscus lineage (genera Fukuyoa and Gambierdiscus) from the western Mediterranean Sea, which is cooler than its eastern basin. Molecular analyses revealed that the Mediterranean strain belongs to F. paulensis and that it bears LSU rDNA sequences identical to New Zealand, Australian, and Brazilian strains. It also shared an identical sequence of the more variable ITS-rDNA with the Brazilian strain. Toxin analyses showed the presence of maitotoxin, 54-deoxyCTX1B, and gambieric acid A. This is the first observation of the two latter compounds in a Fukuyoa strain. Therefore, both Gambierdiscus and Fukuyoa should be considered when as contributing to ciguatera fish poisoning. Different strains of Fukuyoa form a complex of morphologically cryptic lineages where F. paulensis stands as the most distantly related nominal species. The comparison of the ITS2 secondary structures revealed the absence of CBCs among strains. The study of the morphological and molecular traits depicted an unresolved taxonomic scenario impacted by the low strains sampling, Financial support for this research was provided by the Basque Government (project IT699-13). A grant from the University of the Basque Country (UPV/EHU) to H. David also supported this study

The genus Pseudo-nitzschia contains potentially toxic species of problematic taxonomy, making it one of the most intensively studied diatom genera. The study of 35 clonal strains isolated from the Bilbao estuary, an area that experiences recurrent blooms of Pseudo-nitzschia, revealed the presence of two new species, P. abrensis and P. plurisecta, differing from their congeners in both morphology and gene sequence. The morphological features were analyzed by LM and EM, whereas molecular analyses were based on the internal transcribed spacer (ITS) and large subunit (LSU) regions of the rDNA. P. plurisecta appears closely related to P. cuspidata/P. pseudodelicatissima in the phylogenetic tree, whereas P. abrensis forms a moderately supported clade with P. heimii/P. subpacifica and P. caciantha/P. circumpora. Comparison of the secondary structure of ITS2 regions reveals marked differences in the most highly conserved regions among related taxa. Morphologically, the new species differ from their closest congeners in the arrangement of the poroid sectors and the density of valve striae and fibulae. The two species share similar pigment composition, and belong to the group of Pseudo-nitzschia species containing only chlorophyll c2 and c3 .