Dinoflagellates from the Argentine Sea

FABRO, E; ALMANDOZ G. O.

Mar del Plata

Congreso; XVIII Congreso Latino Americano de Ciencias del Mar (COLACMAR); 2019

Dinoflagellatesare of great ecological significance in marine environments, as they oftenrepresent a high proportion of the phototrophic biomass and have a stronginfluence in biogeochemical cycles. Moreover, dinoflagellates comprise severaltoxigenic species, which can produce harmful blooms. In order to describe thediversity and distribution of dinoflagellates in the continental shelf andslope waters of the Argentinean Sea, four oceanographic expeditions werecarried out during autumn, late summer, spring and early summer. Nano- and microplankton abundancewas estimated by the Utermöhl inverted microscope method, whereas optical andscanning electron microscopy was applied for species identification. Dinoflagellateswere observed in 100 % of sampling stations (N= 131), representing on average 10% of the plankton community, but reaching up to 90 % during spring. Theiraverage density varied between 15 x103 cells L-1 duringautumn and 77 x103 cells L-1 during spring, where a maximumabundance of 2.0 x106 cells L-1 was detected. Intense bloomsof Prorocentrum cordatum were registeredin slope waters during spring (1.8 x106 cells L-1), andat southern Buenos Aires Province (265 x103 cells L-1)and Valdes Peninsula (218 x103 cells L-1) during autumn. Also,the potential toxigenic genus Azadiniumreached high densities (1.5 x 105 cells L-1) at slopewaters during spring. During both summer expeditions, small unarmored dinoflagellateswere also abundant (max. 273 x103 cells L-1during early summer),while bigger specimens of the genus Triposreached high abundances (max. 28 x103 cells L-1) duringautumn. This study characterizes the seasonal distribution of dinoflagellatesin the Argentine Sea, highlighting the occurrence of spring blooms in slopewaters.