Drivers shaping phytoplankton diversity and composition in a humid Pampean floodplain lake (Natural Reserve).

DE TEZANOS PINTO, PAULA; LOMBARDO, RUBEN; O'FARRELL, INES; IZAGUIRRE, IRINA

HYDROBIOLOGIA

SPRINGER

Lugar: Berlin; Año: 2015 vol. 752 p. 77 - 89

0018-8158

We aimed toidentify the driver/s of phytoplankton diversity (gamma, beta, alpha) andcommunity composition in a Pampean floodplain wetland (Otamendi), using species and functional groups. Weperformed a seasonal regional survey (2004?2006, phytoplankton regime) acrossthe different aquatic systems in the wetland. Gamma diversity was 254 species.Beta diversity was 2.53 in late spring, 2.49 in winter, and was lowest insummer (2.05) when the wetland was over flooded. Alpha diversity (mean richness) rangedbetween 29 and 50 species. Multiple regressions showed that phytoplankton alphadiversity (richness, Shannon?Wiener, evenness, and Simpson diversity index)responded to dissolved inorganic nitrogen, suspended solids, light attenuation,and pH. Nutrients also explained well the distribution of phytoplanktonfunctional groups. Dissolved inorganic nitrogen concentrations were usuallylimiting in the shallow lakes, whereas phosphate concentration was always high.Light attenuation was mostly caused by high suspended solids and high humicsubstances. We also re-analyzed data from a survey performed during a free-floating plant regime (1998?2000); thedense macrophyte cover attenuates most incoming light into the water column.Compared with the phytoplankton regime, the free-floating plant regime had markedly lowerchlorophyll, lower alpha, higher beta (high heterogeneity among habitats withand without macrophytes), and similar gamma diversity.