Seasonal fluctuations of prokaryotic and eukaryotic phytoplankton in South Patagonian waters

GÓMEZ, M.I.1; ALDER, V.A.

BUENOS AIRES, ARGENTINA

Simposio; 4th OPEN SCIENCE CONFERENCE-SCAR; 2010

Scientific Committee on Antarctic Research

The Antarctic Circumpolar Current (ACC) affects phytoplanktonic production inPatagonian waters (Argentine shelf) through the circulation of the Malvinas Current, which transport nutrient enriched waters over the slope and outer shelf. Until present time, the seasonal fluctuations of the abundance and taxonomic and size structure of phytoplankton in relation with chlorophyll remained practically unknown for this region. In order to start filling this gap, materials collected seasonally in two sectors located at 47º-48º S and 52º-55º S and thus covering the southern Argentine shel slope interface were analyzed. Chlorophyll and phytoplankton biomass concentrations increased during spring and summer. While the northern sector reached highest values in spring due to the prevalence of diatoms (94%), themaxima within the southern sector occurred in summer and were linked to the dominance of dinoflagellates (98%). Results on this seasonal cycle showed that, regardless of latitude, in both summer and autumn the number of siliceous cells (silicoflagellates and diatoms) decreases up to three orders of magnitude while that of dinoflagellates and cyanobacteria exhibits an opposite trend. Nanoflagellates were found to peak in spring-summer whereas the number of picoeukaryotic algae was quite constant throughout the year, with a minimum in spring. General results are expected to contribute to the understanding of regional productivity in contrasting environments under the direct influence of the ACC circulation, such as shelf subantarctic waters and adjacent Antarctic ecosystems.