Abstract ID: 609

Temporal variability of Chlorophyll-a concentration in floodplain lakes in response to seasonality of Amazon River discharge

Four years (2004-2007) of in situ measurements on water and atmospheric variables over a range of temporal scales using an automatic system for environmental monitoring (SIMA) allowed document time changes in chlorophyll concentration at Lago Grande de Curuai (LGC). The lake is located in the Amazon River floodplain, between of Óbidos and Santarém, Pará state, Brazil. LGC has a composite shape and is formed by both drowned mouth of rivers coming from Terra Firme and lakes formed by over bank flooding of scrolls, paleo-streams and coalescent splay deltas. During the high water stage, those lakes of different origin merge to form a unique water body with an area of around 2000 km². The monitoring system (SIMA) was located at a large drowned mouth known as Curuaí, where the alternation of different types of water has already been reported. A time-lagged cross-correlation analysis between daily chlorophyll and water level shows with 95 percent confidence that the highest value (r= - 0,59) corresponded to a negative lag of 10 days. For lags larger and smaller than 50 days the correlation drops and loses statistical significance. The results suggests that at this lake region seasonal changes in Amazon river discharge explains only about 38 % of daily average of chlorophyll concentration. Other system variables such as rain distribution, wind direction and intensity, solar irradiance and floodplain land use should account for the remaining variability.

Session:  Biogeochemistry - Floodplain ecosystem processes.

Presentation Type:  Oral