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, 19-26

Dynamics of organic carbon between the Amazon River and flood plain lakes

P. MOREIRA-TURCQ1, G. BARROUX2, M. BERNARDES3, M.-P. BONET2, L. MAURICE-BOURGOIN2, M. PEREZ3 & P. SEYLER2

1 IRD–Institut de Recherche pour le Developpement, UMR LMTG–Departamento de Geoquímica, Universidade Federal Fluminense, Morro do Valonguinho s/nº, 24020-007 Niterói, Rio de Janeiro, Brazil

pturcq@geoq.uff.br

2 IRD–UMR LMTG, Université Paul Sabatier, 39 allées Jules Guesde, F-31000 Toulouse, France

3 Departamento de Geoquímica, Universidade Federal Fluminense, Morro do Valonguinho s/nº, 24020-007 Niterói, Rio de Janeiro, Brazil

Abstract Water is constantly exchanged between river channels and flood plain lakes. Little is known about the flux at which organic carbon is transferred to and from lakes, and the residence time of flood plain storage. Flux has a special importance for the carbon cycle, especially in the Amazon basin. During four hydrological years organic carbon behaviour and its fluxes were studied in an Amazon flood plain and in the Amazon River. In the Amazon River, particulate organic carbon contents is very constant and represents approx. 2% of the total suspended matter. However, in Amazon flood plain lakes organic carbon content is very variable and represents 2–30% of the total suspended matter and can reach 40–50% of suspended matter during extensive phytoplankton blooms. Dissolved organic carbon is also very variable (5–30 mg l-1) in flood plain lakes, while in the Amazon River its concentration is between 3 and 5 mg l-1. Flood plain lakes are an important source of organic carbon to the Amazon River and are also a sink for Amazon particulate organic carbon.

Key words Amazon River; dynamics; flood plains; organic carbon; organic matter