Microcrustáceos planctónicos y características limnológicas de dos lagunas pampeanas (Buenos Aires,Argentina)

Abstract

In the Pampean Region, there are numerous lagoons of diverse forms, sizes and hydrography. The knowledge about these ecosystems in these lagoons is limited, especially about the plankton present in them. For this reason, the planktonic microcrustaceans and their relationship with the limnological conditions have been studied for two lagoons of the southwest of the Buenos Aires province, Argentina (Unamuno and Calderón lagoons) between October and December of 2006. A study site was selected for each lagoon. Every fifty days biological and physico-chemical samples were taken and environmental parameters were measured. Seven taxa were registered. The density fluctuated between 221 and 1703 ind/l in Unamuno and between 41 and 1401 ind/l in Calderón. Moina eugeniae Olivier 1954 and Boeckella poopoensis Marsh 1906 were the most abundant species, the absence of rotifers was obvious in both lagoons. Few species dominated and the individuals showed great size. The salinity was 0.39 g/l in Unamuno and 1.69 g/l in Calderón so they were characterized as oligohalines. High values of suspended sediments were registered in Calderón. Both lagoons presented low concentrations of silicate and nitrate, and high concentrations of nitrites and phosphates. The silicate concentrations were different between both lagoons. The dominant ions were Na+ and Cl-, so they can be classified as bicarbonate sodium chlorinates. The concentrations of chlorophyll a were important indicating a high algal biomass. These lagoons were different regarding their depth and the concentration of nutrients and ions, as well as the richness and abundance of species. It was clear that the abiotic factors, such as as salinity, were influential over the specific composition. This study offers information on the limnologic, physical, and chemical conditions of two lagoons of the Pampean Region and on the planktonic microcrustaceans that live in these ecosystems. © Asociación Ibérica de Limnología, Madrid, Spain.