Characterisation of organic nitrogen compounds in sediment and leaves of a mangrove ecosystem in north Brazil

The present work deals with nitrogen (N) turnover in different compartments of a mangrove ecosystem and considers various organic N compounds and their availabilities as nutrient sources in order to understand the biotic and abiotic driving forces of N dynamics. Research was conducted on the Braganà §a peninsula in North Brazil, Sediment and leaf samples from field sampling and decomposition experiments were analysed for total nitrogen (TN) and total organic carbon (TOC) content, δ15N and δ13C, amino acid isomer concentrations (D- and L-enantiomers) and total phenols as representative of refractory substances. In conclusion the importance of crabs and fungi in the breakdown of tannins and thus recycling of nutrients within an ecosystem could be demonstrated. The probable input of N into the system through N2-fixation is achieved through the bacterial population, which, in the case of the herbaceous Sesuvium portulacastrum, was associated directly with the plant roots. The findings of this work give important information about N cycling within mangrove ecosystems and identified first clues for the possible restoration of wetland habitats with S. portulacastrum.