Microzooplankton dynamics in the Bahía Blanca Estuary, Argentina

BARRÍA DE CAO, MS; LÓPEZ ABBATE, MA C.; PETTIGROSSO, R; FULCO, K; HOFFMEYER M.S.

Pucón

Simposio; 5th International Zooplankton Production Symosium; 2011

PICES-ICES-COPAS

Microzooplankton (MZ) has a key role in the energy transfer from the primary producers to larger zooplankton.The aim of this study was to analyze the variation of MZ in spring-summer during two years, 2006-2008, inrelation to environmental variables and phytoplankton abundance. Sampling was carried out at six stations alongthe Bahía Blanca Estuary, numbered from 1 (inner) to 6 (outer). Samples were taken with a Van Dorn bottle andfixed with Lugol?s solution. Enumeration of organisms was done with an inverted microscope, following theUtermhöhl´s technique, and biomass was calculated using the morphometric method. The MZ assemblages werecomposed of tintinnids, aloricate ciliates, heterotrophic dinoflagellates, rotifers, and copepod nauplii. MZ biomassranged from 5.0 to 16.2 μg C l-1. Numerical abundance was significantly higher during the 2006/2007 period atstations 4-6. For both studied periods a positive correlation of MZ abundance with temperature, salinity and pHwas found. Also, a negative correlation was observed with turbidity and particulate organic matter (POM). MZcarbon was positively correlated with salinity and pH, but no correlations were found with phytoplankton carbonor chlorophyll a. Using the Bray & Curtis similarity index based on microzooplankton abundance, we found thatstations were associated into three groups: internal (1-2), intermediate (3-4) and external (5-6). Temperature,salinity, pH, turbidity, and POM were the principal factors forcing the temporal dynamics of the MZ in the BahíaBlanca Estuary.