MICROZOOPLANKTON DYNAMICS IN THE BAHÍA BLANCA ESTUARY, ARGENTINA

BARRÍA DE CAO, M.S., LÓPEZ ABBATE, M.C., PETTIGROSSO, R. E., FULCO, K. Y HOFFMEYER, M. S.

Pucón

Simposio; 5th International Zooplankton Production Symposium, Population connections, community dynamics, and climate variability; 2011

Center for Oceanographic Research in the Eastern South Pacifc (COPAS), Universidad de Concepción

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 the MZ in spring-summer during two years, 2006-2008, in relation to the environmental variables and phytoplankton abundance. Sampling was carried out at six stations along the Bahía Blanca Estuary, numerated from 1 (inner) to 6 (outer). Samples were taken with a Van Dorn bottle and fixed with Lugol´s solution. Enumeration of organisms was done with an inverted microscope following the Utermhöhl´s technique and biomass was calculated using the morphometric method. The MZ assemblages were composed by tintinnids, aloricate ciliates, heterotrophic dinoflagellates, rotifers and copepod nauplii. MZ biomass, ranged from 5,0 to 16,2 µgC l-1. Numerical abundance was significantly higher during the 06/07 period in stations 4-6. For both studied periods a positive correlation of MZ abundance with temperature, salinity and pH was found. Also, a negative correlation was observed with turbidity and particulate organic matter (POM). MZ carbon was positively correlated with salinity and pH, but no correlations were found with phytoplankton carbon and chlorophyll-a. Using the Bray & Curtis similarity index based on microzooplancton abundance, we found that stations were associated in 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 Bahía Blanca Estuary.