An organic carbon budget for an Amazon floodplain lake

摘要

Examination of carbon dynamics in lakes has a long and rich history (RIEMANN & SONDERGAARD 1986, WETZEL 2001). As concerns about climate change have intensified, the role of inland waters in the global carbon cycle has received renewed attention and has been found to be disproportion-ately important relative to the area occupied (COLE et al. 2007). While ALIN & JOHNSON (2007) provide a useful summary of production, burial, and lake-atmosphere exchange for large lakes, the number of small lakes in many geographic settings and their cumulative area indicates the necessity of similar analyses for these waters (DOWNING et al. 2006). The fringing floodplain along the 2600 km reach of the Amazon River in Brazil contains about 6500 lakes; this sea-sonally inundated area includes up to about 80 000 km~2 of flooded forests, open water, and floating macrophytes (SIPPEL et al. 1991, 1998, HESS et al. 2003). These habitats out-gas significant amounts of carbon dioxide and methane as a result of carbon fixation on the floodplain and inputs from neighboring uplands (RICHEY et al. 2002, MELACK et al. 2004). However, the relative importance of aquatic versus terrestrial sources of carbon has significant implications for the regional carbon balance and remains uncertain. Based on our measurements and those of others,sufficient data to characterize most of the fluxes and transfor-mations of carbon in a representative central Amazon flood-plain lake (Fig. 1). These results allow quantitative evaluation of the relative importance of aquatic and terrestrial sources of carbon to floodplain emission of greenhouse gases.