IADO   05364
INSTITUTO ARGENTINO DE OCEANOGRAFIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Tidal and seasonal changes in the mesozooplankton community in a highly turbid and mixed estuary
Autor/es:
MARÍA C. MENÉNDEZ; M. SOFIA DUTTO; FLORENCIA BIANCALANA; MARÍA C. PICCOLO; MÓNICA S. HOFFMEYER
Lugar:
Pucón, Chile
Reunión:
Simposio; 5th International Zooplankton Production Symposium; 2011
Resumen:
The aims of this study were (i) to determine the short-term changes of the main taxa within the holo, mero and adventitious plankton in relation to the semidiurnal tidal cycles and (ii) to describe the effect of local winds on this variability. Sampling was carried out bimonthly from December 2004 to May 2006, during 14-h tidal cycles in a fixed station located in the inner zone of the Bahía Blanca Estuary. Zooplankton samples were collected by pumps at 3-h intervals from surface and bottom and hydrological measurements (salinity, temperature, chlorophyll-a, phaeopigments, particulate organic matter and suspended particulate matter) were obtained at each sampling date. All data concerning winds were obtained from a meteorological station and water level was recorded with a tide gauge. Holoplankton was largely dominated by one taxon: the calanoid copepod Acartia tonsa. Meroplankton occurred mainly as polychaetes, barnacle and decapods larvae while benthic harpacticoids and the amphipod Corophium sp. dominated the adventitious fraction. Semidiurnal tide was the main influence on the A. tonsa short-term variability. However, a very different abundance pattern was observed during strong winds events. Meroplankton did not show a clear abundance variation pattern along the tidal cycle. The occurrence of benthic forms in the water column differed among the main taxa, denoting differences between passive and actively swimming organisms. Distributional patterns of harpacticoids seemed to be modulated mainly by velocity asymmetries in the tidal currents, in the same way as suspended particulate matter. However, the Corophium sp. abundance pattern indicated probable behavioural responses associated with tides. Active emergence could be the mechanism by which this species reaches the water column. Results showed that zooplankton community was strongly dependent on allochthonous events and highlighted the role of tides and winds as forcing agents on the community structure. The consequences of the short-term mesozooplankton fluctuations for sampling designs are discussed.