Abundance trends and ecology of planktonic ciliates of the south-western Atlantic (35-63¨¬ S): A comparison between neritic and oceanic environments.

SANTOFERRARA, L.; ALDER VA

JOURNAL OF PLANKTON RESEARCH

Oxford University Press

Lugar: Oxford; Año: 2009 vol. 31 p. 837 - 851

0142-7873

Ciliates from sub-surface waters of the Argentine shelf and the Drake Passage were examined and compared for the first time under austral summer and autumn conditions. In both environments, the taxonomic structure of ciliates was related to temperature and salinity, and aloricate oligotrichs dominated in density (80%) over loricate oligotrichs, litostomatids and prostomatids, while the microplanktonic fraction prevailed in biomass (90%) over the nanociliates. Myrionecta rubra was found all along the Argentine shelf only in autumn, but showing isolated peaks of abundances (103 ind. L-1) during summer. Mean values of density and biomass of total ciliates decreased ca. two-fold from the shelf-slope to oceanic waters, while potential maximum production of aloricate oligotrichs decreased nine times, in relation with the drop in chlorophyll a concentration and the latitudinal decline of temperature, also reflected in maximum growth rates. Fifty percent of total ciliate abundance was caused by local increases (maximum: 20000 ind. L-1 and 25 ¥ìg C L-1), which were spatially superimposed with ranges of seawater temperature and chlorophyll a concentrations of 10-15¨¬ C and 25 0.6-6 ¥ìg L-1, respectively, and were found in the nearby of fronts located in the shelf and the slope.