Brazilian coastal wetland soils (hypersaline tidal flats and seagrasses): soil genesis and biogeochemistry of Fe, Si and C

Abstract

The hypersaline tidal flats, seagrass and other coastal wetlands are ecosystems with great ecological importance, providing nutrients to the ocean and thus playing an important role for coastal productivity. The hypersaline tidal flats constitute the ecological system located between the mangroves and drylands where the evapotranspiration and the low incidence of the tidal floods result in salt accumulation in the soil. On the other hand, the seagrass ecosystems are formed by aquatic phanerogams covering the shallow portion of coastal regions around the globe. Despite the importance of these systems, few studies have been conducted in order to understand the genesis of the soils of these environments and the role that they play in global biogeochemical cycles. This project proposes a set of studies on the genesis of hypersaline plains soils and seagrass meadows along the coast of Brazil and the role of its soils in the dynamics of Fe, Si and C, with the following objectives: (i) conduct a pedological study of soils located in different regions of the Brazilian coast; (Ii) to study the mineralogical assembly of the soil clay fraction; (Iii) to investigate the geochemical environment in order to understand the role of the soil in the biogeochemistry of Fe and Si; (Iv) to investigate the eathering geochemical environment in a hypersaline plain located in northeastern Brazil, in order to understand the role of halomorphic environment in providing Si to the marine environment; (V) to investigate the characteristics of the accumulated organic matter in the soil seagrass, to understand the role of this ecosystem for sequestering C; (Vi) to study microbial communities of the seagrass meadows soil, in order to understand the variations in these communities along the coast and its role in biogeochemical cycles of Fe and C. It is expected with this study to generate information on the hypersaline plain soils and seagrass off the coast of Brazil, in order to understand the role of these ecosystems to global cycles Fe, Si and C, in addition to base future studies related to soil science and other fields of knowledge. (AU)