Abstract

SOSNOVSKY, Alejandro  and  QUIROS, Rolando. The trophic state of small Pampean lakes, its relationship with hydrology and land use intensity. Ecol. austral [online]. 2006, vol.16, n.2, pp.115-124. ISSN 1667-782X.

The trophic state of the Pampean shallow lakes is influenced by the soil fertility and the hydrometeorological conditions as well as by the human activities. The climate of the Pampean region alternates between relatively large periods of drought and flood. In areas where agriculture is intensive, nutrient from excesses in the use of fertilizers can affect the trophic state of lakes. From December 1999 to April 2002, seven small shallow lakes located in the NW of the Buenos Aires province were studied. Changes in the lake depth, water conductivity, nutrients concentrations and chlorophyll a were analyzed. Precipitation was intense during both 2000 and 2001 years. During the first year, the precipitation diluted the high phosphorus concentrations in all the lakes. Despite high precipitation during 2001, the lakes increased their concentrations of phosphorus. These contrasting results could be explained by the different trophic states of the lakes at the beginning of the autumnal precipitation. During the whole study period, algal biomass was more related with nitrogen concentration rather than phosphorous concentration. During the summer season, the lakes generally were under a negative water balance and their nutrients concentrations and algal biomass were high. Nevertheless, the hydrological variability and the agriculture use would alter the physical, chemical and biological parameters of the small Pampean shallow lakes.

Keywords : Shallow lakes; Pampas; Eutrophication.

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