Azadinium (Amphidomataceae, Dinophyceae) in the Southwest Atlantic: In situ and satellite observations

Abstract

Resumen.-Los azaspirácidos (AZAs) son toxinas identificadas en invertebrados marinos y tienen amplia distribución geográfica, no reportadas aún en Argentina ni Uruguay. Aunque el primer agente causal identificado es el dinoflagelado fotosintético Azadinium spinosum, diversos estudios indican que otras especies sintetizan asimismo AZAs. Recientemente se ha detectado la presencia de A. cf. spinosum en el Atlántico Sudoccidental y la generación de dos extensas floraciones como nuevos eventos a escala global. En este estudio se analiza la distribución geográfica regional y desarrollo temporal de Azadinium así como las condiciones ecológicas de una tercera floración de A. cf. spinosum y su registro satelital. Azadinium presentó una amplia distribución que abarcó el norte de la plataforma de Argentina y sur de Uruguay, incluyendo la desembocadura del Río de la Plata, con abundancias generalmente bajas (<1x10 3 células L -1 ); un estudio en una estación de serie de tiempo mostró una marcada estacionalidad con mayores abundancias en primavera y otoño. La tercera floración (>10 6 células L -1 ) de A. cf. spinosum ocurrió en agosto-septiembre 1998 en un área coincidente con las previas, en condiciones hidrográficas propicias para su crecimiento poblacional. Esta floración comprobada in situ tuvo registros satelitales del sensor SeaWiFS que indicaron altas concentraciones de clorofila-a (máximo: 11,76 mg Clo-a m -3 ) dentro de una ancha y larga banda (al menos 2,5° de latitud) adyacente al talud continental y la Corriente de Malvinas. Aún desconocemos si las especies de Azadinium presentes en el Atlántico Sudoccidental son capaces de sintetizar AZAs, tema de interés debido a la explotación de bivalvos en bancos de profundidad. Palabras clave: Azadinium, floraciones de dinoflagelados, Atlántico Sudoccidental, SeaWiFSAbstract.-Azaspiracid toxins (AZAs) have been identified in marine invertebrates and are of wide geographical distribution, but have not been reported in Argentina or Uruguay. The first identified causal agent is the photosynthetic dinoflagellate Azadinium spinosum, but new studies indicate that other species also synthesize AZAs. We have recently reported the presence of A. cf. spinosum in the Southwest Atlantic and the generation of two extended blooms as new global events. Here we analyze the ecological conditions of a third bloom of A. cf. spinosum and its satellite record, and report the regional distribution and temporal development of the genus Azadinium. Azadinium had a wide spatial distribution encompassing northern Argentine and southern Uruguayan shelves, including the mouth of the Río de la Plata. Abundance was generally low (<1x10 3 cells L -1 ), and analysis conducted at a time series station showed a marked seasonality in spring and autumn. A. cf. spinosum caused a third bloom and discolorations (>10 6 cells L -1 ) in August-September 1998 in the northern shelf of Argentina in an area that spatially coincided with the previous episodes, with hydrographic conditions propitious for its population gr...

Azadinium poporum from the Argentine Continental Shelf, Southwestern Atlantic, produces azaspiracid-2 and azaspiracid-2 phosphate

“…spinosum occurred in spring at low water temperature (< 10 8C), Azadinium spp. at the coastal station was recorded during the warm periods in summer and autumn as well (Akselman et al, 2014) which might indicate the presence of several species of Azadinium with different ecological requirements in Argentinean waters.…”

“…A more detailed investigation on the seasonal and interannual variability of Azadinium spp. conducted at a fixed station close to the Argentinean coast (Akselman et al, 2014) from 1994 to 2000 revealed Azadinium to be present in all years but in low abundance and sporadically. Nevertheless, whereas the offshore blooms of A. cf.…”

“…Previous South Atlantic blooms of Azadinium have been described to occur in spring or even in late winter (Akselman and Negri, 2012;Akselman et al, 2014), but these blooms refer to another species (Azadinium cf. spinosum), and occurred farther offshore along extensive areas of the middle shelf and near the shelf break (Akselman and Negri, 2012;Akselman et al, 2014). Coastal populations of A. poporum, however, may have a different seasonality.…”

“…presence of a ventral pore) of the Argentinean species needed to be clarified. Very recently, a retrospective description of a third bloom of the same species in 1998 was published (Akselman et al, 2014). Furthermore, additional cruise and time series data of the Argentinean Sea indicate a rather wide spatial distribution of Azadinium encompassing the northern Argentine and southern Uruguayan shelf including the mouth of Rio de la Plata (Akselman et al, 2014).…”

“…Recurrent blooms of Azadinium in 1990, 1991(Akselman and Negri, 2012Akselman et al, 2014) provided indications that cyst beds and cyst hatching may provide an important inoculum for local Azadinium populations. A number of dinoflagellates are known to produce cysts, mainly as a dormant, zygotic stage of their life cycle (Pfiester and Anderson, 1987).…”