Dynamics and Biogeochemistry of River Corridors and Wetlands (Proceedings of symposium S4 held during the Seventh IAHS Scientific Assembly at Foz do Iguaçu, Brazil, April 2005). IAHS Publ. 294, 2005., 159-166

Abstract The reassessment of biogeochemical data originally collected in the Paraná River between 1981 and 1984 highlights the role played by the long (~1200 km) and wide (~30 km) flood plain during the 1982–1983 ENSO-triggered exceptional flood. DOC is the only major biogeochemical variable that showed high (early flood stages) and low (late flood stages) concentrations during very high discharges (>22000 m³ s^-1). Other variables, such as PCO₂, DIC, and the POC : PN ratio appeared to be more markedly affected by materials stored in the flood plain during the periods between successive extraordinary floods (the ENSO recurrence interval is 2–4 years), which are flushed out when such extreme events occur. TSS concentrations also decreased markedly during the high flood mainly because the over bank stage and lower water surface slopes implied lower water velocities and, hence, diminished sediment carrying capacity.

Key words biogeochemistry; carbon; dissolved organic matter; ENSO; flooding; fluvial dynamics; Paraná River; particulate organic matter