Interação do regime hídrico com as relações nutricionais em ecossistema manguezal

Abstract

Interação do regime hídrico com as relações nutricionais em ecossistema manguezal RESUMO (Interação do regime hídrico com as relações nutricionais em ecossistema manguezal). A hipótese de que a sazonalidade do regime fl uvial e pluvial tenha alguma infl uência na composição físico-química do sedimento e na constituição química foliar em arbóreas do ecossistema manguezal foi testada nesse estudo. ABSTRACT(Interaction of the water regime with nutrients relations in a mangrove ecosystem). Th e hypothesis that the seasonality of rainfall and the river regime have some infl uence on the physical and chemical sediment and chemical composition of tree leaves of the mangrove ecosystem was tested. In this study, the infl uence of the hydric regime on the physicochemical characteristics of the Mucuri River mangrove ecosystem, in Bahia, Brazil, was evaluated. Th e 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 infl uenced by the hydric regime. Th e 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. Th e hydric regime also infl uenced the chemical composition of leaves. During the dry season, the concentrations of Ca, Mg, Zn, Fe and Cu were higher. Spatial variation and interspecifi c diff erences were also observed. Leaves of A. germinans showed a higher accumulation of nutrients, while lower concentration of nutrients were observed in R. mangle. Th e basin forest region (interior of forest) was characterized by high values of organic matter, pH and K. Th ese factors had little infl uence on the concentration of nutrients in the leaves. Th e 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.

Distribution of Cu, Fe, Mn, and Zn in Two Mangroves of Southern Brazil

“…In the studied areas, the differences in Fe, Mn, Cu, and Zn concentrations in the soils, both between the species and mangroves could be related to temporal (Cuzzuol and Rocha 2012) and spatial variations, which were linked to the chemical and physical characteristics of the soil (Bernini et al 2006;. Tides variation also interfered on the availability of chemical elements (Lacerda et al 1986), resulting in a concentration/dilution effect on the nutrients of this ecosystem (Ong Che 1999).…”

“…Evidence of low correlation between the metals in the soil and leaf tissues (Bhosale 1979;Peterson et al 1979;Sadiq and Zaidi 1994;Cuzzuol and Rocha 2012) may indicate a low bioavailability, and/or a high selectivity of the plants (MacFarlane et al 2003). The analytical procedures do not consistently reveal the complexity of bioavailability, distribution, and assimilation processes of the elements affecting the plants (Parker et al 2001).…”

“…In fact, soils retain metals in different fractions and are submitted to the hydrodynamic variations typical of the ecosystem (Saenger and McConchie 2004;Cuzzuol and Rocha 2012), while tissues act as bioindicators (MacFarlane et al 2003). Evidence of low correlation between the metals in the soil and leaf tissues (Bhosale 1979;Peterson et al 1979;Sadiq and Zaidi 1994;Cuzzuol and Rocha 2012) may indicate a low bioavailability, and/or a high selectivity of the plants (MacFarlane et al 2003).…”

“…The analytical procedures do not consistently reveal the complexity of bioavailability, distribution, and assimilation processes of the elements affecting the plants (Parker et al 2001). Despite this limitation, altogether, these procedures suggest that mangroves act as an efficient biogeochemical barrier to metal transport (Cuzzuol and Rocha 2012). The dual role of Cu, Fe, Mn, and Zn, which can be either nutrients, or toxic elements in mangrove ecosystems, has been addressed by several studies (MacFarlane et al 2003;Andrade et al 2005;Kannappan et al 2012).…”

“…The dual role of Cu, Fe, Mn, and Zn, which can be either nutrients, or toxic elements in mangrove ecosystems, has been addressed by several studies (MacFarlane et al 2003;Andrade et al 2005;Kannappan et al 2012). They also have been investigated for their physiological functions together with the mechanisms that control their absorption or exclusion in the plants that grow in this ecosystem (Machado et al 2002;Cuzzuol and Rocha 2012). Given this context, this study tested the relation between the Cu, Fe, Mn, and Zn content of the soils and leaf tissues of plants from two mangroves located on the Parana coastline.…”