Search

Microplastics (particles with a size < 5 mm), one of the most emerging aquatic pollutants, are of particular concern since they can reach high densities and interact with biotic and abiotic environment. The occurrence of microplastics in freshwater systems is less understood than in marine environment. Hence, the present study aims to provide new insights into microplastics abundances and distribution in Antuã River (Portugal) by applying the isolation method of wet peroxide oxidation with addition of zinc chloride to water and sediment samples collected in March and October 2016, in three sampling sites. The abundance of microplastics in water ranged from 5 to 8.3 mg m −3 or 58–193 items m −3 in March and from 5.8–51.7 mg m −3 or 71–1265 items m −3 in October. In sediments, the abundance ranged from 13.5–52.7 mg kg −1 or 100–629 items kg −1 in March and from 2.6–71.4 mg kg −1 or 18–514 items kg −1 in October. The water and sediment samples with the greatest abundances were from São João da Madeira and Aguincheira, respectively. Spatio-temporal distribution showed different pattern according to methodological approaches, seasonal and hydrodynamic conditions and the proximity to urban/industry areas. Analysis of plastics by Fourier transform infrared spectroscopy underline polyethylene and polypropylene as the most common polymer types identified in this work. The low medium high oxidation ratio was 56:22:22 (%) in March and 61:31:8 (%) in October. Foams and fibers were the most abundant type in São João da Madeira, while fibers and fragments were the most abundant in Aguincheira and Estarreja in water and sediment samples, respectively. This study emphasizes the importance of rivers as carriage systems of microplastics. Further studies should be performed to identify point sources in order to mitigate the microplastics contamination in aquatic systems. [ABSTRACT FROM AUTHOR]

Studies that address the potential effects of climate and land use changes on surface water quality are scarce in the Mediterranean region. In the present work, the impacts of climate and land use changes on nutrient and copper exports from a humid Mediterranean catchment (São Lourenço) were evaluated using the SWAT model. SWAT reproduced reasonably well total nitrogen (TN), phosphorus (TP) and copper (Cu) exports in São Lourenço, providing an adequate baseline scenario as well as a suitable model parameterization for assessing the impacts of climate and land use changes under the A1B and B1 emission scenarios for the end of the 21st century (2071-2100). Land use changes scenarios were generated along the same storylines as climate change scenarios to assess the combined effects of the two stressors. Climate changes itself led to a decline in annual TN and TP exports under both emission scenarios mostly due to a decrease in runoff and erosion induced by a reduction in rainfall, but it hardly affected Cu exports largely due to its strong immobilization in soils. Land use changes per se resulted in an increase in streamflow, but the changes in water quality varied markedly according to the scenarios. A substantial decrease in TN, TP and Cu exports was observed under scenario A1B, due to a reduction in vineyard areas. Under scenario B1, however, TP exports decreased much less while TN exports hardly changed, reflecting differences in the preferential transport pathways of these compounds. Cu exports also remained the same, as no changes occurred in the vineyard areas. The combination of climate and land use change scenarios revealed additive impacts on the exports of all three contaminants, emphasizing the importance of integrated approaches to define adaptive land management practices that can ensure the future sustainability of Mediterranean water resources. [ABSTRACT FROM AUTHOR]

Risk assessment of pesticides has been based on direct toxic effects on aquatic organisms. Indirect effects data are taken into account but with limitations, as it is frequently difficult to predict their real impacts in the ecosystems. In this context the main aim of this work was to assess how the exposure to the herbicide pendimethalin (Prowl ® ), under environmentally relevant concentrations, may compromise the nutritional composition of food for a relevant group of primary consumers of freshwater food webs—the daphnids, thus affecting their reproduction performance and subsequently the long-term sustainability of active populations of this grazer. Therefore, Daphnia magna individuals were chronically exposed in a clean medium to a control diet (NCF – i.e., non-contaminated green algae Raphidocelis subcapitata ) and to a contaminated diet (CF – i.e., the same monoalgal culture grown in a medium enriched with pendimethalin in a concentration equivalent to the EC 20 for growth inhibition of algae), during which reproductive endpoints were assessed. The algae were analysed for protein, carbohydrate and fatty acid content. The chemical composition of R. subcapitata in the CF revealed a slight decrease on total fatty acid levels, with a particular decrease of essential ω9 monounsaturated fatty acids. In contrast, the protein content was high in the CF. D. magna exposed to CF experienced a 16% reduction in reproduction, measured as the total number of offspring produced per female. Additionally, an internal pendimethalin body burden of 4.226 μg g −1 was accumulated by daphnids fed with CF. Hence, although it is difficult to discriminate the contribution of the pesticide (as a toxic agent transferred through the food web) from that of the food with a poor quality—compromised by the same pesticide, there are no doubts that, under environmentally relevant concentrations of pesticides, both pathways may compromise the populations of freshwater grazers in the long term, with consequences in the control of the primary productivity of these systems. [ABSTRACT FROM AUTHOR]

This study concerned the mid-term regeneration of the woody understory vegetation of pure and mixed stands of Pinus pinaster Ait. and Eucalyptus globulus Labill. in northern and central Portugal following wildfires in 2005 and 2006. Pine and eucalypt stands are the most widespread and most fire-prone forest types in Portugal. The main aim was to investigate the importance of biogeography, topography, forest type and post-fire management operations in explaining the patterns in shrub diversity (species richness) and abundance (cover). To this end, 284 study sites in four distinct biogeographic regions were sampled 5 to 7 years following the last wildfire. At each site, the presence and cover of individual shrub species were estimated using 4 sub-plot of approximately 10 m 2 each. The entire data set was analyzed by means of GLM using a total of seven explanatory variables: biogeographic region, forest type, three types post-fire management operations (soil tillage, tree harvesting, and shrub clearance), and two topographic variables (slope angle and elevation). The GLM analysis was also done for the individual biogeographic regions. Biogeographic region and slope steepness were key factors explaining shrub species richness, albeit the role of slope angle was possibly linked to the intensity of past land use. Biogeographic region equally played a significant role in explaining the cover of all shrubs together as well as of the shrubs of Leguminosae and Cistaceae. All three types of post-fire management operations appeared to hamper the recovery of resprouters and Leguminosae, whereas just tree harvesting and shrub clearance (but not soil tillage) negatively affected the cover of seeder species. These impacts of post-fire management operations had a noticeable region-specific component, being more relevant in the less productive biogeographic regions. Also the role of forest type depended strongly on biogeographic region. It was only significant in the South Mediterranean region, where pine plantations had a higher total shrub cover as well as higher covers of seeders and Cistaceae. Possibly, however, this significant role of forest type could be due to the lower incidence of shrub clearance in the pine stands. [ABSTRACT FROM AUTHOR]

Abstract: Lake Vela is a polymictic shallow lake exhibiting some characteristics typical of an advanced trophic state, namely, the permanently turbid water, the reduction in biodiversity, and the recurrent occurrence of Cyanobacteria blooms, which occasionally lead to large fish kills. This study was carried out in order to understand the seasonal variation of Lake Vela’s phytoplankton and cladoceran communities and their interactions under advanced eutrophic conditions. When comparing our results with general models of plankton succession observed in other temperate and tropical lakes we found some coherence between several seasonal events. Our results suggest that phytoplankton is mainly regulated by nutrients (“bottom-up” effect). However, the warm mediterranean temperatures had an important role in the phytoplankton succession, being responsible for the rapid and intense Cyanobacteria development in spring and summer. Our work also demonstrated that phytoplankton is one of the main factors responsible for the seasonal structure of the community of cladocerans, which are well related to changes in algae diversity and abundance, being the Cyanobacteria having major impact. Moreover, the occurrence of a massive Cyanobacteria bloom during the study, which induced anoxia and consequent fish kill, enhanced the structuring role that fish have on the cladoceran seasonal succession and the effects of this episode in the normal seasonal succession of plankton. [Copyright &y& Elsevier]

• Plastics used in daily life are of extreme scientific and societal concern. • PE, PP, PET, PS, PA and PVC are the most common polymers used in our daily life. • Plastics can be found in the environment and food sources (exposure routes). • Daily use of plastics can cause toxic impacts on environment and human health. • Additives are more toxic than monomers to human-beings and wildlife. Plastics are indispensable and persistent materials used in daily life that can be fragmented into micro- or nanoplastics. They are long polymer chains mixed with additives that can be toxic when in contact with distinct species. The toxicity can result from polymer matrix, additives, degradation products and adsorbed contaminants. Notwithstanding, there is still an immense gap of information concerning the individual and mixed impacts of plastics. Hence, in this study, we characterize the most common plastic materials widely used in our daily life by its polymer type and compile the environmental and human health hazards of these polymers including the impacts of monomers, additives, degradation products and adsorbed contaminants based on literature review. In summary, polyvinyl chloride is the most toxic polymer type used daily (monomer and additives); additives are more toxic than monomers to wildlife and humans; and the most toxic additives are benzene, phthalates and lead stabilisers. [ABSTRACT FROM AUTHOR]

Highlights: [•] We modeled the post-fire occurrence of native and exotic trees in burned plantations. [•] Native trees occurred in 50% of the plots, showing post-fire conversion potential. [•] Alien invasive species occurred in 10% of the plots. [•] Ecological region and post-fire management were the key drivers of occurrence. [•] Typical post-fire management actions promote invasives and hinder native species. [Copyright &y& Elsevier]

Abstract Freshwater ecosystems face widespread diffuse and point-source contamination. Species Sensitivity Distributions (SSDs) have been used as a tool to determine chemical concentration benchmarks that represent protective levels for most species in the environment. Here we used a SSD approach to assess on the adequacy of standard planktonic organisms to reflect the response of benthic communities, critically supporting the structure and function of lotic ecosystems. For the purpose, SSDs reflecting non-lethal responses of standard planktonic and selected benthic organisms were built based on EC50 values (collected in the literature or estimated following testing herein) regarding three model contaminants: potassium dichromate (PD), 3,5-dichlorophenol (DCP) and lead chloride (LC). The derived HC5 estimates were discriminatory between chemicals and the uncertainty associated with the estimate was remarkably low. The HC5 estimates with corresponding uncertainty were generally within the same order of magnitude for the three chemicals tested, with better discrimination between chemicals regarding their hazardous potential being achieved for benthic organisms: DCP was clearly less hazardous than PD, but LC tends to be as hazardous as PD and DCP (assuming the confidence interval ranges). Moreover, benthic communities were more sensitive to both DCP and PD, in this later case the HC5 being lower by more than one order of magnitude than that found for planktonic communities; for LC, confidence intervals overlapped, preventing a feasible assumption regarding differential sensitivity of the compared communities. Microphytobenthos was highlighted as the most sensitive group to the three tested chemicals in SSDs covering the benthic compartment, while SSDs with planktonic organisms did not consistently show trends in sensitivity ordering. Overall, our results suggest that protective benchmarks retrieved from SSDs built with the responses of standard planktonic organisms (which are the most commonly used for regulation purposes) do not adequately protect benthic communities. Graphical abstract Unlabelled Image Highlights • Sensitivity to reference chemicals was assessed regarding standard planktonic species. • Sensitivity to reference chemicals was also assessed for selected benthic species. • The HC5 discriminated sensitivity between planktonic and benthic organisms. • Planktonic species exhibited no consistent pattern in sensitivity ordering. • N. libonensis was the most sensitive benthic species to the tested chemicals. [ABSTRACT FROM AUTHOR]

The accumulation of plastics in aquatic systems constitutes an emerging scientific and societal concern, because of their ubiquity, high persistence and insufficient management by sewage and wastewater treatment processes. Microplastics (<5 mm), a group of particles differing in physico-chemical properties (e.g. size, shape, colour, density and polymer type), are of particular concern as they can reach high densities and can interact with biotic and abiotic environment. Moreover, potential of bioaccumulation increases with decreasing of particle size. Although microplastics have been widely investigated in marine systems, very little attention is paid to freshwater systems. As the concern about microplastics started appearing recently, there is no unified method for microplastic isolation, which result in inconsistent data that differs in quality and resolution. Hence, this work aims to assess the effectiveness of distinct isolation methods as an attempt to identify and establish a unified method for environmental monitoring of aquatic systems. For that, artificial samples containing eleven plastics belonging to the most common types of polymers (e.g. low/high-density polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate) were prepared and subjected to different methods, including density separation methods using sugar, olive oil and zinc chloride, as well as organic matter degradation methods with hydrogen peroxide (wet peroxide oxidation) and multienzymatic detergent (enzymatic digestion). The samples then underwent the detection, quantification, and identification of polymers using a stereomicroscope and Fourier transform infrared spectroscopy (FTIR). Several criteria were considered in order to achieve the aims of this work: efficiency of density separation and organic matter degradation, the total mass of recovered polymers, cost of each procedure, the time spent with each method, the simplicity, and the quality of recovered polymers. Based on this multi-criteria approach, this study concludes that the wet peroxide oxidation with addition of zinc chloride was the most effective method. [ABSTRACT FROM AUTHOR]

Conventional management of Mediterranean vineyards strongly contributes to land degradation. In Portugal, the use of integrated production has been encouraged by governmental subsidies because it is assumed to be a farm management system that protects the environment and favours agriculture sustainability. The purpose of this study is to assess the impact of minimum tillage and regulated fertilization practices, driven by integrated production, on runoff and associated sediment and nutrient exports (total phosphorous – TP, total nitrogen – TN and nitrates – NO 3 ). A vineyard in the Bairrada wine region was instrumented with six runoff plots (80–122 m 2 ). Plots were monitored on a weekly to bi-weekly basis (depending on the rainfall pattern), over two hydrological years (from October 2012 to September 2014). Results indicated that annual runoff coefficients ranged from 10% to 20%, sediment losses from 1.1 to 29.0 Mg ha −1  yr −1 , TP exports from 0.4 to 6.5 kg ha −1  yr −1 , TN exports from 0.2 to 20.0 kg ha −1  yr −1 and NO 3 exports from 0.1 to 0.8 kg ha −1  yr −1 . These results highlight the susceptibility of vineyards to land degradation and their role as a diffuse source of pollution. Rainfall strongly influenced runoff as well as sediment and nutrient concentrations, leading to relevant inter-annual and seasonal differences. Over the study period, about 60% of runoff and >85% of sediments and nutrients exported by runoff were recorded during winter. Management practices, namely inter-row tillage deeply influenced sediment exports, whereas fertilization, had a strong effect on nitrate exports. Although integrated production lead to lower runoff and nutrient exports than conventional viticulture, additional measures are needed to effectively prevent soil erosion and nutrient losses in Mediterranean vineyards. [ABSTRACT FROM AUTHOR]

The impacts of climate and land use changes on streamflow and sediment export were evaluated for a humid (São Lourenço) and a dry (Guadalupe) Mediterranean catchment, using the SWAT model. SWAT was able to produce viable streamflow and sediment export simulations for both catchments, which provided a baseline for investigating climate and land use changes under the A1B and B1 emission scenarios for 2071–2100. Compared to the baseline scenario (1971–2000), climate change scenarios showed a decrease in annual rainfall for both catchments (humid: − 12%; dry: − 8%), together with strong increases in rainfall during winter. Land use changes were derived from a socio-economic storyline in which traditional agriculture is replaced by more profitable land uses (i.e. corn and commercial forestry at the humid site; sunflower at the dry site). Climate change projections showed a decrease in streamflow for both catchments, whereas sediment export decreased only for the São Lourenço catchment. Land use changes resulted in an increase in streamflow, but the erosive response differed between catchments. The combination of climate and land use change scenarios led to a reduction in streamflow for both catchments, suggesting a domain of the climatic response. As for sediments, contrasting results were observed for the humid (A1B: − 29%; B1: − 22%) and dry catchment (A1B: + 222%; B1: + 5%), which is mainly due to differences in the present-day and forecasted vegetation types. The results highlight the importance of climate-induced land-use change impacts, which could be similar to or more severe than the direct impacts of climate change alone. [ABSTRACT FROM AUTHOR]