Presence Of Tributaries Research Articles

What Are Lake Beaches Made of? An Assessment of Plastic Beach Litter on the Shores of Como Bay (Italy)

Plastic waste dispersion is a well-recognized environmental threat, despite continuous efforts towards improving waste disposal management over the last few decades. Plastic litter is known to strongly impact upon water bodies and shorelines, affecting the health of ecosystems and impacting upon the aesthetic value of sites. Moreover, plastic waste that is abandoned on beaches contributes towards different degradation processes that potentially lead to the formation of secondary microplastics (MPs), with likely cascade effects upon the whole ecosystem. In this view, this study aims to characterize the plastic beach litter found on the shores of the western basin of Como Lake (Italy) to better understand the origin of MPs in littoral sediments, including the recognition of object typologies and the chemical characterization of polymers using Fourier-transformed infrared analysis (FTIR). The results highlighted that the most abundant polymers on beaches are polypropylene (PP) and polyethylene (PE), representing 73% of the collected polymers. This confirms that floating, low-density polymers are more likely to accumulate on beaches. Moreover, almost 66% of litter is represented by commonly used manufactured items (disposable objects, packaging, and everyday items). This evidence, combined with the analysis of the main environmental features of the sampling sites (the main winds, distance to urban areas, and the presence of tributaries) indicate that abundance of beached litter is mainly linked to beach accessibility and the local winds. These results highlight that multiple factors affect the environmental fate of plastic litter and give insights into the assessment of secondary microplastics in beach sediments.

Revisiting the concept of longitudinal gradients in reservoirs

Abstract: Aim Reservoirs are an increasingly common type of aquatic ecosystem in countries where hydropower is a dominant energy source. Understanding the functioning of these systems is essential to establish monitoring strategies or priorities for their use. The main goal of this study was to test for the presence of longitudinal gradients in reservoirs. Methods We gathered data along the main axes of 17 tropical reservoirs to test the relationship between different ecological indicators (e.g., turbidity, nutrient concentrations, and phytoplankton abundance) and distance to the dam. After, we tested whether the strengths of longitudinal gradients were related to a set of explanatory variables (occurrence in a reservoir cascade, presence of tributaries near the dam, land-use, morphology and reservoir age). Results We did not find significant relationships between our set of ecological indicators and distance to the dam and the strengths of these relationships were not consistently predicted by the explanatory variables. However, different indicators suggested patterns consistent with expectations. Conclusion The distance to the dam is not a consistent predictor of the spatial variation of different limnological variables in tropical reservoirs, highlighting a high degree of context-dependency.

Estado trófico na cascata de reservatórios de um rio no semiárido brasileiro

The present study evaluated the influence of the river flow on the trophic state of the reservoir cascade located between the medium and lower São Francisco River, through quaterly samplings between December 2007 and September 2008, at the reservoirs of Sobradinho, Itaparica, Moxotó, Paulo Afonso-I, II, III, Paulo Afonso-IV and Xingó. The variables analysed were inflow and outflow, and water transparency, chlorophyll-a, total phosphorous and reactive soluble phosphorous used to calculate the trophic state indexes. Sobradinho differed from the other reservoirs for all variables and indexes analysed, and was regarded as eutrophic and mesotrophic. Itaparica, Moxotó, Paulo Afonso-I,I I, III and Paulo Afonso-IV reservoirs presented a similar seasonal variation and trophic state varying from mesotrophic to oligotrophic. A water oligotrophication along the reservoir cascade was detected, whose effect was attenuated by river contributions (Pajeú and Moxotó rivers), and effluents from the cities located along the system, mainly Paulo Afonso, in the state of Bahia. Sobradinho reservoir presented the typical trophic condition of a system charger (eutrophic - mesotrophic), while those between Itaparica and PA-IV are subject to the modifications associated with the presence of tributaries and bordering cities, whereas Xingó presents a prevailing oligotrophic condition. Seasonally, only the trophic state of Sobradinho differed during the study period, and the other reservoirs presented a similar pattern between them, and little trophic variation between months. The reservoirs located on the medium and submedium stretches showed a downstream tendency of oligotrophication, depending on their relative position along the cascade, being subject to a seasonal variation of their trophic status according to Sobradinho reservoir outflow, and the operational use of water for energy generation at each power plant along the cascade.