MICROZOOPLANKTON COMMUNITY IN THE CHUBUT RIVER ESTUARY, ARGENTINA

BARRIA DE CAO, M.S.; PERILLO, G.M.E.; PEREZ, D.; PICCOLO, M.C.; HELBLING, W.

Bahía Blanca

Congreso; ECSA 44: SCIENCE AND MANAGEMENT OF ESTUARIES AND COASTS: A TALE OF TWO HEMISPHERES; 2008

Estuarine Coastal Science Association-Instituto Argentino de Oceanografía

Species composition, abundance and seasonal variation of microzooplankton (20-200 µm) from the Chubut River Estuary were studied from samples collected during a year (July 2006 to June 2007) in different tidal conditions. The estuary is as salt wedge system in high tide and well-mixed freshwater at low tide. This is the first report on the microzooplankton from the area. Enumeration of the organisms was done with an inverted microscope following the Utermhöl´s method. Surface temperature, salinity, nutrients, chlorophyll “a” and phaeopigments were measured simultaneously with the sampling. The microzooplankton community was characterized by ciliates, thecamebians, foraminifers, rotifers and nauplii. During strong fluvial influence (salinity: 0.6 to 18), the total microzooplankton abundance ranged from 60 to 600 individuals l-1. Ciliates were the most abundant group in winter, comprising 59.6 % of the total microzooplankton abundance, while thecamebians dominated during summer (89 %). Under marine influence (salinity: >18 to 32), the total abundance ranged from 40 to 500 ind. l-1 and the most conspicuous group were the ciliates, comprising 82.6 % of the total abundance during winter, and 76 % during autumn. Salinity changes did not influence the microzooplankton abundance, but species composition was highly dependent on salinity.