Nutrient dynamics in the deltaic floodplain of the Lower Parana River

BONETTO, C.; DE CABO, L.; GABELLONE, N.; VINOCUR, A.; DONADELLI, J.; UNREIN, F.

Archiv für Hydrobiologie

E. Schweizerbart'sche Verlagsbuchhandlung

Año: 1994 vol. 131 p. 277 - 295

1863-9135

Nitrogen and phosphorus concentration were simultaneously measured in the Lower Paraná R., in a floodplain lake in permanently contact with the river, and the surrounding marsh in the deltaic tidal floodplain of the river, where a variable amount of water is daily exchanged between river floodplain depending on tidal amplitude, wind action and river discharge. Suspended matter N & P content was assessed in the Lower and Upper Paraná and Bermejo Rivers, together with the lake bottom and marsh sediments. Nitrogen and P exchange in the lake sediment-water interface was estimated by means of cores laboratory incubations. Nutrient limitation for plant growth was studied by mean of bioassays. A large suspended matter and nitrate decrease from the river to the lake and marsh was observed. SRP decreased from the river to the lake surface, but increase in the suboxic lake bottom, the water hyacinth ring and the marsh, as well as oxygen depleted cores incubations. Present results suggest that deltaic floodplains represent a sink of N and a source of SRP, derived from the river suspended matter. Differences in N & P concentration between the Middle and Lower Paraná stretches were consistent with this fact. Schoenoplectus californicus, the dominant macrophyte in the marsh was shown to be N limited. Evidence was presented suggesting N limitation for Eichhornia crassipes, the dominant macrophyte in the lake. Phytoplankton bioassays did not provide a definite pattern probably shifting frequently from nutrient and to light limitation.