The hypothesis that the seasonality of rainfall and the river regime have some influence on the physical and chemical sediment and chemical composition of tree leaves of the mangrove ecosystem was tested. In this study, the influence of the hydric regime on the physicochemical characteristics of the Mucuri River mangrove ecosystem, in Bahia, Brazil, was evaluated. The study was carried out during the months of April (rainy season) and October (dry season) in sites that were predominantly comprised of Avicennia germinans, Laguncularia racemosa and Rhizophora mangle. We evaluated the physicochemical properties of the sediments and nutrient leaf composition. Overall, the results were influenced by the hydric regime. The period of higher river levels and rainwater intake was marked by high values of exchangeable bases, cation exchange capacity, pH, salinity and Ca, Fe and Mn in the sediments. In contrast, higher values of K, Mg and Zn occurred during the dry season. The hydric regime also influenced the chemical composition of leaves. During the dry season, the concentrations of Ca, Mg, Zn, Fe and Cu were higher. Spatial variation and interspecific differences were also observed. Leaves of A. germinans showed a higher accumulation of nutrients, while lower concentration of nutrients were observed in R. mangle. The basin forest region (interior of forest) was characterized by high values of organic matter, pH and K. These factors had little influence on the concentration of nutrients in the leaves. The lack of a clear seasonal pattern in geomorphology, geochemistry and in the chemical composition of the leaves shows the complexity of interpreting data of a coastal ecosystem where environmental factors interact synergistically and antagonistically.
Avicennia germinans; Laguncularia racemosa; nutrients; Rhizophora mangle; seasonality; sediments
