Climate change is a challenge that humanity must face in the coming decades. Coastlines will be affected due to the rise in sea level. Thus, biogeochemistry information about estuarine environment, such as mangrove ecosystems, is very important to better understand which impacts can occur due to natural or anthropogenic changes. This book was structured in four chapters and describe our research that has been performed in a mangrove ecosystem located at Espírito Santo state, Southeast Brazil. A biogeochemical study was performed to assess the chemical composition and speciation of mangrove soil and tree by X-ray fluorescence (XRF) and absorption (XANES) spectroscopy techniques, collected in synchrotron radiation laboratories (SSRL-USA and LNLS-Brazil). This book shows how spectroscopy analysis can provide valuable geochemistry information about mangrove ecosystem. We assessed the influences of sea water and preservation status in chemical content and sulfur speciation of mangrovesoil profiles by XRF and XANES analysis. Also, at the first time, a Ca K-edge XANES analysis has been successfully applied to dendrochemistry study in Tropical mangrove. Enjoy!