Abstract
AIM: Catalão Lake was surveyed between 2002 and 2011 with the aim of studying seasonality of the flow of nutrients between water, sediment and aquatic macrophytes. The role of the flood pulse and the ecological mechanisms influencing the forest-water interactions in the Amazon floodplain were discussed; METHODS: Catalão Lake is located in the Amazon floodplain (03º 08'-03º 14' S and 59º 53'-59º 58' W), near the confluence of the Solimões and Negro rivers, approximately 3000 m from the port of CEASA, near the city of Manaus. It is considered to be a mixed water lake because it receives white waters rich in sediments from the Solimões River and black waters with humic substances from the Negro River. Physical and chemical parameters including C, N and P levels were studied in the diverse compartments, and a flux model was developed; RESULTS: There is a strong nutritional (C, N and P) and ionic (Na+, K+, Ca2+, Mg2+, Cl-, HCO3-, CO3(2-) and SO4(2-)) flow from the rivers to the lake. The highest C:N:P ratio was found in Paspalum repens which, during periods of drought, played an important role in releaseing nutrients into the water. The connectivity of the lake with the rivers ensured a high variation of transparency and nutrient content, fundamental for biological processes. A model of the nutrient flow, interaction and connectivity between ecosystems, and the influence of the hydrological cycle has been developed.
Highlights
The wetlands of the floodplain areas can be defined as transition systems between aquatic and terrestrial ecosystems, where according to Junk (1983), various compartments are in constant interaction, influenced mainly by the flood pulse of the region
The aquatic macrophyte communities have an important role in the flow of nutrients within lake ecosystem, contributing significantly to the physical and biological diversity, habitat structure, nutrient storage and ecological functioning of the lakes (Junk and HowardWilliams, 1984; Piedade, 1988; Darwich, 1995; Baattrup-Pedersen et al, 2003; Baattrup-Pedersen and Riis, 2004; Cotton et al, 2006; Lacoul and Freedman, 2006; Pedersen et al, 2006)
Among many aspects that could be addressed in this study we attempted to answer the following questions: What is the influence of the flood pulse in mixed floodplain lakes of the Amazon? What are the main ecological processes and mechanisms of forest-water interaction in these lakes? For this, we identified the routes of flow of nutrients (C-N-P) and the seasonal ionic balance in the water, sediment and aquatic macrophytes compartments
Summary
The wetlands of the floodplain areas can be defined as transition systems between aquatic and terrestrial ecosystems, where according to Junk (1983), various compartments are in constant interaction, influenced mainly by the flood pulse of the region. In the Amazon floodplain there are lakes, which undergo periodic changes in the volume of water and nutrient concentrations due to the influence of the flood pulse (Junk, 1997; notes of the authors). During the flood river water invades the lakes, which return to the river in the ebb These exchanges of water cause periodic changes in the concentration of nutrients, energy flow, abundance and biodiversity in the aquatic ecosystem (Junk, 1983; Ferreira and Stohlgren, 1999; notes of the authors)
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