The marine dinophycean genus Azadinium has been identified as the primary source of azaspiracids (AZA), a group of lipophilic phycotoxins known to accumulate in shellfish. Blooms of Azadinium in the southern Atlantic off Argentina have been described from the 1990s, but due to a lack of cultures, the diversity of South-Atlantic Azadinium has not yet been fully explored and their toxin production potential is completely unknown. During a spring 2010 research cruise covering the El Rinco´n (ER) estuarine system (North Patagonian coast, Argentina, Southwestern Atlantic) a search was conducted for the presence of Azadinium. Although neither Azadinium cells nor AZA in field plankton samples were detected, 10 clonal strains of Azadinium poporum were successfuly established by incubation of sediment samples. Argentinean A. poporum were more variable in size and shape than the type description but conformed to it by the presence of multiple pyrenoids with starch sheath, in plate pattern and arrangement, and in the position of the ventral pore located on the left side of the pore plate. In contrast to all previous description of A. poporum, isolates of the Argentinean A. poporum possessed a distinct field of pores on the second antapical plate. Conspecificity of the Argentinean isolates with A. poporum was confirmed by molecular phylogeny of concatenated ITS and LSU rDNA sequences, where all Argentinean isolates together with some Chinese A. poporum strains formed a well-supported ribotype clade within A. poporum. All isolates produced AZA with the same profile, consisting of AZA-2 as the major compound and, to a lesser extent, its phosphated form. This is the first report of a phosphated marine algal toxin. This first confirmation of the presence of AZA producing Azadinium in the Argentinean coastal area underlines the risk of AZA shellfish contamination episodes in the Southwestern Atlantic region.
Keywords: AZADINIUM; AZASPIRACIDS; SOUTHWESTERN ATLANTIC; ARGENTINA; AZASPIRACIDS; ARGENTINA; Oceanografía, Hidrología, Recursos Hídricos; Ciencias de la Tierra y relacionadas con el Medio Ambiente; CIENCIAS NATURALES Y EXACTAS.
Keywords: Botánica; Diatomeas marinas; Bacilariofíceas.
Field measurements of surface chlorophyll-a concentration were used to evaluate for the first time the performance of the standard Moderate Resolution Imaging Spectroradiometer (MODIS) and both standard and regional Sea-viewing Wide Field-of-view Sensor (SeaWiFS) ocean colour algorithms in the Patagonian Continental Shelf (PCS) between 38u S and 55u S. The results showed that the regional algorithms did not significantly improve the global algorithm estimates. Moreover, the SeaWiFS OC4v4 algorithm, National Aeronautics and Space Administration (NASA) standard chlorophyll product, showed the best performance among all the algorithms examined. Nonetheless, all the global and local algorithms analysed showed uncertainties dependent on chlorophyll concentration. Low chlorophyll-a concentration values tended to be overestimated and high values tended to be underestimated. A regional analysis within the PCS showed that higher uncertainties are found in the homogeneous side of the tidal fronts present in the PCS, in areas suggested to be optically complex case 2 waters, while a better result (less bias) was obtained in the southern mid-shelf region. We discuss the probable reasons and provide possible explanations of the regional differences in the performance of the algorithms.
Keywords: Imágenes satelitales; Clorofila; Atlántico Sur; algoritmos; Otras Ciencias Naturales y Exactas; Otras Ciencias Naturales y Exactas; CIENCIAS NATURALES Y EXACTAS.