Organic-walled dinoflagellate cyst: recording harmful/potentially harmful species from recent and fossil sediments. Examples from Argentine Continental Shelf.

BOREL, C.M.

Calfuco, Valdivia.

Workshop; First meeting IGCP Project No. 681 History of Toxic Phytoplankton in Patagonia. Work plan and protocols for sediment analysis.; 2019

Coastal Laboratory of Aquatic Resources, Universidad Austral de Chile

The analysis of the distribution and abundance of the organic-walled dinoflagellate cysts (dinocysts) from the surface sediments allows to recording dinocyst-producing species, still when the motile vegetative stages have not yet been observed in the water. Recent investigations detected a significative variability of the dinocyst assemblages in the San Jorge Gulf, Argentina, with high proportions of autotrophic taxa in the mouth and south coastal area linked to a stratified water mass conditions. Also were recognized viable cysts of potential toxic dinoflagellate in these sediments, principally Protoceratium reticulatum and Gonyaulax spinifera complex. Protoceratium reticulatum cysts are well represented in the water-sediment interface of a wide geographical area in a considerably extension of the latitudinal range (~35° to 53°S), showing its presence from Uruguayan shelf waters up to the Patagonian shelf, the mouth of the Magellan Strait and north of Tierra del Fuego, having also found its motile cells at the northern shelf break zone at depths of ~1530 m. More records on the spatio-temporal distribution of benthic and planktonic stages of species of Gonyaulacaceae, Amphidomataceae and Gymnodiniaceae are necessary in order to assess the risk potential of toxic episodes in this Southwestern Atlantic region.