Vanesa Yael Bohn

Shallow lakes from the Central Plains of Argentina: an overview and worldwide comparative analysis of their basic limnological features

The Central Plains of Argentina is a heterogeneous environment, but the lakes there share some fundamental features: they are all shallow and polymictic as being well exposed to wind. First, we provide a synthesis of the climate, geology, and hydrological network. We also discussed shallow lakes origin and their limnological and biological salient features. Second, we focus on Pampean shallow lakes from a global perspective, comparing the limnological variables: total phosphorus concentration (TP), total nitrogen concentration (TN), chlorophyll a (Chl a) concentrations, and Secchi disk reading (SD) from a compiled database. No significant differences in the Chl a vs. TP relationship were found between Pampean and other shallow lakes. Otherwise, the chlorophyll yield per unit of phosphorus of Pampean lakes is similar to the world shallow lakes average. Moreover, the relationship SD vs. Chl a differed significantly between Pampean and the remaining world lakes, about 50–60%. When confronted against other lakes worldwide, Pampean shallow lakes depart from most of them as having higher TP, TN, and Chl a concentrations and much lower SD transparency, and therefore they stand as extremes of the trophic-state continuum. Despite their highly turbid state, these lakes provide valuable ecosystem services that are highly appreciated and mobilize important economic resources.

Assessment of climate variability and land use effect on shallow lakes in temperate plains of Argentina

Areal variation in lakes is closely associated with other factors such as intensity of land use of the hydrological basins, climatology, geomorphology and depth. The main objective of this study is to assess the relationship between climatic variability events (El Niño Southern Oscillation, ENSO), land use and shallow lakes’ areal variations in the temperate plains of Argentina for the period 2002–2011. The standard precipitation evaporation index (SPEI) was employed in this study in conjunction with the oceanic Niño index (ONI) and in situ annual precipitation data to determine wet, dry and normal years. Shallow lakes’ areal variation was analyzed by satellite imagery (MODIS) processing and the variability of the land use intensity was determined based on agricultural estimations. Frequency in the maximum of shallow lake areas was relatively more dependent on any changes in the rainfall regime (ENSO events) than in the land use (decrease/increase of the cultivated area). The El Niño (2002/3) and La Niña (2007/8) events clearly affected the precipitations of the total studied lake regions, with maximum areas in 2002 and minimum in 2008. The results obtained may be an important contribution to mitigate flooding and droughts in the studied area.

Efecto de la Variabilidad Climática Sobre el Estado de la Vegetación y la Cobertura de Agua en una Cuenca de Clima Templado (Argentina)

El area de estudio se encuentra en el sur de la provincia de Buenos Aires (Argentina) y forma parte de la region pampeana Argentina. Se caracteriza por el predominio de un clima templado. El objetivo de este trabajo fue cuantificar los efectos de los eventos climaticos extremos en el estado de la vegetacion y la extension del area cubierta por agua, en una cuenca hidrografica de clima templado (cuenca del arroyo Naposta Chico). El periodo de estudio fue 2000-2013. La metodologia incluyo el analisis de serie de datos del Indice Estandarizado de Precipitacion y Evapotranspiracion (SPEI) a escala 1, 3 y 12 meses, para la deteccion de eventos climaticos extremos. Mediante interpretacion visual de imagenes satelitales, se determinaron las diferentes coberturas de la cuenca y se calculo el Indice de Vegetacion de Diferencia Normalizada (en ingles, NDVI). Ademas, se delinearon los cuerpos de agua del area de estudio mediante procesamiento digital de imagenes satelitales Landsat 5 TM y 7 ETM+ correspondientes a los eventos extremos definidos mediante la aplicacion del SPEI. Los mismos fueron definidos para 2001 y 2004 (eventos humedos), 2008 y 2009 (eventos secos) y 2007 (evento normal). El estado de la vegetacion asi como tambien las extensiones cubiertas por los cuerpos de agua, presentaron variaciones a lo largo de los diferentes eventos climaticos extremos. La vulnerabilidad climatica de la cuenca y el conocimiento de los eventos de precipitacion extremos es fundamental para la gestion de los recursos hidricos y de las actividades agroeconomicas que alli se desarrollan.