Photosynthetic picoplankton in Argentina lakes

Abstract

This article provides an overview of the studies on photosynthetic picoplankton (PPP) carried out in water bodies from different latitudes of Argentina, including Patagonian lakes and shallow lakes from the Chaco-Pampean Plain Region. The PPP of the different aquatic systems: shallow and deep lakes, turbid and transparent water bodies, and lakes with contrasting trophic state are characterized. We focus our attention on light intensity as the major axes of niche differentiation in Pcy. We present examples regarding the distribution of distinct Pcy ecotypes adapted to high- and low-light intensities at different depths in the water column of deep and shallow transparent lakes. In ultraoligotrophic Patagonian lakes phycoerythrin (PE)-rich picocyanobacteria (Pcy) are dominant, whereas eutrophic and hypertrophic shallow lakes from the Pampa Plain present a wide range of PPP abundances dominated by phycocyanin (PC)-rich Pcy. The relevance of the depth of the euphotic layer and nutrient concentration as the main abiotic features explaining the variability encountered are discussed. The PPP from eutrophic shallow lakes and relict oxbow lakes from wetlands from the Lower Paraná Basin are mainly represented by PCrich Pcy, and Peuk in a lesser extent. Changes in the free-floating plants coverage were found to play a crucial role in structuring the PPP, and on the other hand, there is evidence of a negative relation between the PPP abundance and the hydrometric level. For different aquatic systems the PPP populations are compared by means of the patterns resulting from the flow cytometry analyses.