The Paraguay and Bermejo rivers

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

Fitoplancton de Argentina

CRAMER

Año: 2012;

This chapter describes the phytoplankton of the Paraguay and Bermejo rivers, with emphasis on the spatial and temporal patterns of composition, density, biomass, diversity and size structure. The phytoplankton of the Paraguay River was characterised by the dominance of small Chlorophyceae and Cryptophyceae, with a gradual increase of Bacillariophyceae towards its confluence with the Paraná River. The dominance in biomass corresponded to Aulacoseira granulata and A. herzogii. In the northern stretch where the Pantanal drains, this group exceptionally shared the dominance with Chlorophyceae and Euglenophyceae. Small Chlorophyceae prevailed in transparent waters whereas Aulacoseira predominated throughout the main channel as related to a higher turbulence and lower water transparency. Density, biomass, diversity and species richness presented an inverse relationship with the hydrometric level. Such attributes were positively correlated with water temperature, presenting a decrease from north to south in relation to increased suspended solids and conductivity and decreased water transparency. The Bermejo River, main tributary of the Paraguay River in its lower section, was the main determinant of the sharp decrease in the main attributes of the phytoplankton in the low Paraguay.