Two strains of Prorocentrum texanum (LPCc020 and LPCc032) were established from coastal waters of the Province of Buenos Aires, Argentina. Field and cultured materials were examined using light and scanning electron microscopy, and the planktonic species Prorocentrum texanum, a known okadaic acid producer, was identified. We compared morphology, genetics and toxin profile of P. texanum based on material from Argentina in relation to strains from the Gulf of México. Our specimens and those described in the protologue of P. texanum var. texanum had similar shape, thecal ornamentation distribution patterns of large and small pores, and morphology of wings supported by platelets 1 and 4, respectively. Morphometric differences occurred in the ranges of length, depth and diameter of thecal plate pores. Morphology of the periflagellar area was described from Argentinean strains. SSU, ITS and LSU rDNA-based phylogenies of strains LPCc020 and LPCc032 placed them with other sequences of P. texanum. ITS rDNA showed that the most closely species, in order, are P. micans, P. steidingerae, P. mexicanum/P. rhathymum, and P. koreanum. The ability of the Argentinian strains to produce marine biotoxins was assessed, but, no toxins were detected. This is the first report of P. texanum outside the Gulf of México.

A new species of the marine dinophyte genus Heterocapsa Stein is described. Two clonal strains originating from Argentinean coastal waters were examined with light and electron microscopy and LSU and ITS rDNA sequence data were obtained. Heterocapsa claromecoensis sp. nov. is described as a distinctive species with a conical epitheca, a similar sized and rounded hypotheca, a single reticulate chloroplast situated in the periphery of the cell, and a large pyrenoid in the episome, above an ellipsoidal to rounded nucleus in the hyposome. The plate tabulation pattern of Po (pore plate), cp (cover plate), X (X-plate or canal plate), 5ꞌ, 3a, 7ꞌꞌ, 6c, 5s, 5ꞌꞌꞌ, 2ꞌꞌꞌꞌ was as for most other species of Heterocapsa. H. claromecoensis sp. nov. differs from all other species of Heterocapsa by the microarchitecture of two different types of organic body scales, which uniquely were different in height. Phylogenetic trees based on LSU and ITS rDNA sequences placed H. claromecoensis in a separate branch, with a sequence assigned to H. orientalis being the closest match based on LSU rDNA.

In the framework of a monitoring program of harmful microalgae from the marine coastal waters of the Buenos Aires Province, seven strains were isolated and characterized by morphological and molecular analysis (LSU rDNA partial sequencing, D1–D3 regions). Established strains belonged to Alexandrium catenella, Protoceratium reticulatum and Pseudo-nitzschia multiseries. The toxinological profile of the target strains were determined by UHPLC-FLD equipment for paralytic shellfish toxins (PSTs) and LC-MS/MS for lipophilic (LSTs) and amnesic toxins (ASTs). The toxin profile varied in the four strains of A. catenella, the predominant compounds were gonyautoxins (GTXs) GTX2,3 and GTX1,4 for strains LPCc001 and LPCc004, and N-sulfocarbamoyl toxins (Cs) C1,2 and GTX1,4 for strains LPCc002 and LPCc008. The obtained cellular toxicity values were moderate-to-high (12.38–46.40 pg saxitoxin equiv. cell⁻¹). The toxin profile of P. reticulatum was dominated by yessotoxins (YTXs) (up to 94.40 pg cell⁻¹) accompanied by homo-yessotoxin (Homo-YTX) traces. In P. multiseries, the toxin profiles were dominated by domoic acid (DA) (1.62 pg cell⁻¹ and 1.09 pg cell⁻¹) and secondarily by Isomer A (Iso-A), Epi-domoic acid (Epi-DA), Isomer-E (Iso-E) and Isomer-D (Iso-D). This study provides detailed information about representative HAB species in the area, useful for resource management, risk evaluation and related research on toxic dinoflagellates and diatoms.

En el marco de un programa de monitoreo de fitoplancton y biotoxinas implementado desde 2008 en aguas marinas costeras de la Provincia de Buenos Aires (Argentina), ha sido aislada la cepa LPCc022 de un dinoflagelado woloszynskioide, nanoplanctónico, de paredes delgadas. La filogenia basada en LSU rDNA mostró que la cepa aislada pertenecía a un clado molecular correspondiente a Biecheleria brevisulcata. B. brevisulcata puede ser diferenciada mediante microscopía óptica de las especies B. baltica, B. halophila, B. cincta y B. tirezensis sobre la base de la ubicación del núcleo en la célula, el rango de tamaño de las células y los ambientes que habitan. Este es el primer reporte del género Biecheleria y la especie B. brevisulcata en Argentina y en general en aguas del Atlántico sudoccidental.

In the framework of a phytoplankton and biotoxin monitoring program implemented since 2008 in marine coastal waters of the Buenos Aires Province (Argentina), a gymnodinioid, photosynthetic dinoflagellate was isolated from a sample collected in Santa Teresita, establishing the strain LPCc007. The strain was identified as belonging to the psammophilic genus Togula by light microscopy based on the following distinctive characters: morphology of the cell dorso-ventrally flattened, and course of the cingulum, highly asymmetric, descending, with its ends displaced by about one to two thirds of the total length of the cell and joined by an oblique intercingular groove. The comparative morphological analysis between the motile vegetative cells of the isolated strain and the three species of the genus described to date, did not reveal significant differences that would allow it to be determined at a specific level. Instead, the pattern of development of longitudinal grooves on the hypocone of cells about to undergo mitosis observed in strain LPCc007, perfectly agrees with that described for T. jolla as a differential character. The morphological identification was consistent with LSU rDNA (D1-D2) based phylogeny that showed the sequence aggregation in the T. jolla clade. This is the first report of the genus Togula and the species T. jolla from Argentina and the South-West Atlantic Ocean coastal waters.