Influence of Hydrogeomorphic Variability on Physicochemical and Biological Conditions in the Water Column of a Tropical Alluvial Zone

Abstract The variability of 11 physicochemical and biological variables in the water column was analyzed in lentic and lotic environments during two intraannual water level periods over 10 non-consecutive years within a hydraulically interconnected alluvial zone of a tropical fluvial system. The evaluation included the limnological characterization, a principal component analysis (PCA) based on eight key variables, and the examination of inherent and recurrent variability of data through violin plots. The limnological characterization and PCA, both based on variable-level analysis, partially explained the variation among four conditions: lotic high water level, lentic high water level, lotic low water level, and lentic low water level. Whereas, the analysis of inherent data variability pointed out three conditions associated with kinetic energy and water column processes. First, the fluvial explained primarily by sediment transport and nutrient enrichment. Second, lateral homogenization of electric conductivity, water transparency and dissolved oxygen saturation. Third, lentic in low water level, when lakes worked as bioreactors exhibiting high biology productivity and oxygen supersaturation. In conclusion, the inherent data variability of the key variables supports the hypothesis that the physicochemical variability is driven by recurrent and interactive conditions. These findings show that the analysis of data variability provides a useful tool for understanding water column dynamics and identifying the principal conditions regulating the ecological functioning of tropical riverine wetlands.