Macrophyte assemblages in relation to environmental, temporal and spatial variations in lakes of a subtropical floodplain-river system, Argentina

Abstract

This work analyses the variation in the structure of macrophyte assemblages in relation to environmental (lake morphometry and water physico-chemistry), temporal and spatial variables, in seven floodplain lakes placed in the surrounding of the Salado and the Paraná Rivers confluence in the Paraná floodplain-river system. We recorded the variations in cover of thirteen of the most important macrophyte species among rooted and free-floating life forms. A discriminant analysis of the main coordinates showed significant differences among floodplain lakes (spatial variation), as well as among the 13 months studied (temporal variation). Redundancy analysis indicated that electrical conductivity, maximum depth, shoreline development index, lake area and water temperature had significant influence on macrophyte assemblages. In a partial RDA, environmental and temporal variables accounted for a similar percentage of total explained variation (∼50%), whereas spatial variables, including distance to main channel, accounted for 30.6%. Results show that the environmental variables of lakes, temporal descriptors, and the spatial position of lakes along the floodplain can explain a significant fraction of variation of macrophyte assemblages. These results allow us to understand the dynamic of macrophyte assemblages along temporal and spatial scales and their association with flooding regime, considering local (physico-chemical and morphometric) and landscape (spatial) characteristics of the floodplain environments.