Photosynthetic picoplankton in Argentinean lakes

IZAGUIRRE, I.; UNREIN, F.; MODENUTTI, B. ; ALLENDE, L.

Freshwater phytoplankton from Argentina

Cramer

Año: 2013;

In this chapter we present a review 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. We characterise the PPP of the different aquatic systems, including: shallow and deep lakes, turbid and transparent water bodies, and lakes with contrasting trophic state. In ultraoligotrophic Patagonian lakes picocyanobacteria (Pcy) are dominant, composed mainly by phycoerythrin (PE)-rich Synechococcus spp. 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 of Argentina. In addition we discuss the competition with other phytoplanktonic species presenting data on photosynthetic efficiency of the different groups. Eutrophic and hypertrophic shallow lakes from the Pampa Plain present a wide range of PPP abundances dominated by phycocyanin (PC)-rich Pcy in all shallow lakes. In clear-vegetated systems the importance of picophytoplankton over total phytoplankton is marked, whereas in turbid shallow lakes no single pattern is evident. We discuss the relevance of the depth of the euphotic layer and the nutrient concentration as the main abiotic features explaining the variability encountered. The PPP from eutrophic shallow lakes and relictual oxbow lakes (ROLs) from Otamendi Wetland are mainly represented by PC-rich 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 in this wetland, and on the other hand, there is evidence of a negative relation between the PPP abundance and the hydrometric level. For different aquatic systems we compare the PPP populations by means of the patterns resulting from the flow cytometry analyses.