ZOOPLANKTON DYNAMIC IN A SALT LAKE OF THE SEMIARID ARGENTINEAN PAMPA

KOPPRIO, G. A.; BIANCALANA, F.; HOFFMEYER, M. S.; BERASATEGUI, A.; PAGGI, J. C.; JOSÉ DE PAGGI, S.

Córdoba

Conferencia; 11th International Conference on Salt Lake Research Laguna Mar Chiquita (Córdoba – Argentina); 2011

PROMAR, Univerisidad Nacional de Córdoba, ISSLR

Lake Chasicó is a large salt lake with an extension of ~ 12,000 Ha and salinity of ~20 and characterized for an unstable hydrology. In order to protect the fish populations of Odontesthes bonariensis and the native vegetation, this water body together with the adjacent area was declared to be a nature reserve of the Buenos Aires province. Aim of this work is to describe the biodiversity and to contribute to the understanding of the seasonal ecology of halophilic zooplankton in Lake Chasicó. The calanoid copepod Boeckella poopoensis dominated in abundance and biomass during the study period. This species is typical of inland salt lakes of South America and tolerate salinities up to 90. The female with eggs of B. poopoensis were abundant during the whole year and no reproductive seasonality was inferred. The partenogenetic females of the cladoceran Moina eugeniae were found mainly during summer, while the sexual females and male in autumn. The highest abundance of M. eugeniae coincided with one of the lowest values of transparency and a drop in the chlorophyll a summer values, suggesting a high effectively filtration and a strong top-down regulation over phytoplankton. The rotifer Brachionus plicatilis shows the highest abundance in March in the sampling station near the river. B. plicatilis was particularly abundant during the second part of the sampling period. The increment of dissolved organic carbon (2000µM) was related to a top down regulation of bacterial biomass by microzooplankton predation, especially by the rotifer B. plicatilis directly, or indirectly through Protozoa. Other species with low abundance were the harpacticoid copepod Cletocampus deitersi and the rotifer Hexarthra sp. Lake Chasicó, as is typical of salt lakes, is characterized by a low zooplankton biodiversity.