Phytoplankton of the Chaco Pampean Plain

YOLANDA ZALOCAR DE DOMITROVIC; DEVERCELLI, MELINA; FORASTIER MARINA E.

Fitoplancton de Argentina

CRAMER

Año: 2012;

This chapter summarises the characteristics of phytoplankton of the Chaco Pampa Plain between the Pilcomayo River (25º15’S; 57º45’W) and Salado River (31º39’S; 60º45’W) towards the Paraguay-Paraná system. This subtropical area has a climate gradient from east (wet) to west (arid). Rivers and streams have a seasonal regime, with floods in autumn and dry periods at the end of winter. Hydrological fluctuations appear as the driving forces of phytoplanktic community. During low waters (flow reduction and increase in salinity), diversity was reduced and density of euryhaline species was increased. The highest algal development was observed during an extraordinary low water period (La Niña). In occasions of environmental stability and high temperatures, water-bloom of Anabaenopsis arnoldii, A. nadsonii and Nodularia harveyana were recorded. The lenitic environments of the western region (arid) show marked fluctuations in extension and depth and could dry during periods of scarce precipitations. Phytoplankton density is low and represented by small Chlorococcales and Euglenophyceae. Water-blooms of Anabaena spp. and Cylindrospermopsis raciborskii are frequent. In shallow lakes and wetlands of the eastern region (wet) with macrophytes and high organic matter, Cryptophyceae, Chlorococcales and a wide variety of species of Euglenophyceae and diatoms dominated. The Ramsar Site called “Humedales Chaco” has the greatest diversity of species in this region.