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The formation of man-made reservoirs generates several impacts on water quality. In order to minimize some of these impacts mathematical models are currently used. This paper aims to discuss the issue associated with the degradation of plant resources (leaves, branches, barks and litter) that remain within the watershed of the new man-made lakes and parameterize a kinetic model related to decay of plant detritus. In these environments, the short-term variation of limnological parameters is mainly connected with biomass decay drowned during the filling operation. The kinetics of the degradation processes in reservoirs are discussed on the basis of information with related to detritus sources and the chemical properties of different types of compounds (i.e. labile and refractory fractions). Overall, the parameterization of the (first order) kinetic model showed that refractory fractions (ca. 86%) are predominant and the mineralization is a slow process, constituting the main route for decomposition and being affected by changes of environmental variables. The mineralization of labile and hydrosoluble compounds (ca. 14%) is responsible for the short-term water quality variation owing to decomposition; basically, the intensities of these changes depend on the labile/soluble compounds content of detritus and its chemical composition. [Copyright &y& Elsevier]

Salt marshes are well-known sinks of carbon and nitrogen, incorporating them both into sediment and in the halophyte biomass, being key players in the estuarine biogeochemical cycles. Due to aboveground senescence there will inevitably occur losses of C and N rich detritus, becoming prone to the tidal flooding and hydrodynamic regime. On the other hand, the ongoing climate change effects, such as sea level rise (SLR) are known to have influence in the estuarine circulation. The Ria de Aveiro is a mesotidal lagoon located in the Northwestern Portuguese coast, presenting a very complex geometry and characterized by large areas of salt marshes and tidal flats distributed along a web of narrow channels. Residual circulation, tidal asymmetry, tidal dissipation and detritus Lagrangian trajectories were determined from numerical modelling results of the MOHID 2D model that was applied to each coastal system, considering the actual sea level and a sea level rise (SLR) scenario. The results here discussed show that in the case of Ria de Aveiro, the examined salt marsh exports about 15 kg C m-2 y-1 and 2 kg N m-2 y-1. Nowadays, Barra salt marsh presents the highest values of residual circulation, but predictions point out to its reduction due to SLR scenario. Barra salt marsh shows highly dynamic conditions by being exposed to higher current velocities, increased erosion rates and longer and more frequent inundation periods. This way, model results of Lagrangian particles indicate that the detrital particles are highly dispersed, with large amounts approaching the outer area of the lagoon, a feature that is highly enhanced in the SLR scenario. These features may have two major implications: (1) enhance the fuelling of secondary production in the coastal shelf and (2) excessive N exports and possible eutrophication of the coastal area. These two consequences (positive and negative) acquire even more importance if all the marsh extension along all the Ria de Aveiro is considered along with its elevated amount of plant-generated detritus. Regarding the present predictions and concerns on estuarine ecology in a global change framework, it becomes important to consider these estuarine salt marshes not only as possible nutrient sinks, but also as a potential N source enhanced by the ongoing climate changes. [ABSTRACT FROM AUTHOR]