Our aim was to quantify microplastic ingestion by fish assemblages in two tropical Brazilian estuaries and to evaluate whether biological and ecological factors influence the ingestion of ...microplastics by fish species. Of 2233 fish from both estuaries (from 69 species) examined in this study, 9% of the individuals (24 species) had microplastics in their gut contents. Microplastic ingestion occurred irrespective of fish size and functional group. The diet of fish species was analyzed based on prey items identified in the fish's full stomach contents and five feeding guilds were defined. Microplastics were common throughout all feeding guilds. Low (average ingestion values 1.06±0.30 items/total fish) but widespread occurrence among estuaries also indicates proliferation of microplastic pollution. Our findings highlight the need to focus on assemblage level studies to understand the real magnitude of the problem and emphasize the urgency of mitigation measures directed at microplastic pollution in estuarine ecosystems.
•We analyzed microplastic ingestion in 69 fish species collected along two estuaries.•Microplastic ingestion was widespread in fish assemblages in two tropical estuaries.•Microplastic ingestion was independent of fish size and fish functional groups.•Microplastics were observed in fish from five different feeding guilds.•The level of anthropogenic pressures did not influence microplastic ingestion.
► Estuarine meiofauna communities were studied spatially and seasonally. ► Nematodes are considered good indicators of ecological status of estuaries. ► Communities followed the estuarine gradient, ...with a low temporal variability. ► Diversity and ecological indices presented different classification of the stretches. ► Ecological status of estuaries must integrate taxonomic and functional approaches of nematodes communities.
Estuarine meiofauna communities have been only recently considered to be good indicators of ecological quality, exhibiting several advantages over macrofauna, such as their small size, high abundance, rapid generation times and absence of a planktonic phase. In estuaries we must account not only for a great natural variability along the estuarine gradient (e.g. sediment type and dynamics, oxygen availability, temperature and flow speed) but also for the existence of anthropogenic pressures (e.g. high local population density, presence of harbors and dredging activities).
Spatial and temporal biodiversity patterns of meiofauna and free-living marine nematodes were studied in the Mondego estuary (Portugal). Both taxonomic and functional approaches were applied to nematode communities in order to describe the community structure and to relate it with the environmental parameters along the estuary. At all sampling events, nematode assemblages reflected the estuarine gradient, and salinity and grain size composition were confirmed to be the main abiotic factors controlling the distribution of the assemblages.
Moreover, the low temporal variability may indicate that natural variability is superimposed by the anthropogenic pressures present in some areas of the estuary. The characterization of both meiofauna and nematode assemblages highlighted the usefulness of the integration of both taxonomic and functional attributes, which must be taken into consideration when assessing the ecological status of estuaries.
The functional diversity of fish communities was studied along the salinity gradient of two estuaries in Northeast Brazil subjected to different anthropogenic pressures, to gain a better ...understanding of the response of fish communities to disturbance. We evaluated functional complementarity indices, redundancy and analysed functional composition through functional groups based on combinations of different traits. The fish communities in both estuaries share similar functions performed by few functional groups. The upstream areas had generally lower taxonomic, functional diversity and lower redundancy, suggesting greater vulnerability to impacts caused by human activities. Biomass was slightly more evenly distributed among functional groups in the less disturbed estuary, but total biomass and redundancy were lower in comparison to the urbanized estuary. The present findings lend strength to the notion that the less disturbed estuary may be more susceptible to anthropogenic impacts, underscoring the need for more effective conservation measures directed at this estuary.
•Functional diversity was studied in two tropical estuaries with different impacts.•Fish communities share similar functions performed by few functional groups.•Distinct salinity sectors exhibit different degrees of vulnerability.•The less impacted estuary was considered more vulnerable to disturbance.•More effective management measures are suggested for both estuaries.
Ecosystem functioning is assessed through research that spans multiple biological organisational levels and disciplines, and it is quantified by measuring the magnitude and dynamics of several ...processes. This quantification is done using different tools, and the resulting information from each tool is often interpreted independently. Our main aim was to contribute to the understanding of the functioning of tropical estuarine ecosystems facing anthropogenic impact, using information on fish diversity, traits and food webs. We used biological and environmental data from 2 Brazilian estuaries with different levels and types of human disturbance: the heavily impacted Paraiba estuary and the environmentally protected Mamanguape estuary (IUCN, Protected Area Category V). Fish assemblages and their prey were collected along the salinity gradient in the dry and wet seasons, and we evaluated (1) species taxonomic diversity, (2) functional diversity based on effect traits and (3) food-web structure through analyses of the natural abundance of stable isotopes (carbon and nitrogen). Species turnover, i.e. the change in species identity, along each estuary was relatively high, and this dissimilarity was considerably greater than the trait turnover (i.e. low functional β-diversity). These results highlight that, although habitat selection was an important driver of the coexistence of fish species due to spatial environmental gradients, the competition for resources might be high because species tended to use the system in a similar way. The relatively narrow range of both δ13C and δ15N values among fish species also implies competition for the same resources. Moreover, the δ15N values indicated anthropogenic inputs of nitrogen in both estuaries, regardless of their protection framework, which highlights the need for more effective conservation measures.
The aim of this paper is to indicate the overall economic efficacy of competing uses of estuarine resources by integrating ecological value, water uses and ecosystem services into the DPSIR ...conceptual framework as an added value for policy making and management. The complex interactions between the socio-economic system and the ecosystem (as part of the ‘integral system’ as suggested by the second author before) require generic but still ‘tailor made’ techniques to quantify all relevant variables and to provide an integral view of the system’s status. One of the few techniques that can assist in structuring such complex data in an integrative way is the Drivers-Pressures-Status-Impacts-Responses (DPSIR) approach. Support and regulatory services (such as water supply and water quality) are essential to sustain crucial ecosystem processes and functions while the water required for human activities (water demand) is an essential system service. With the help of DPSIR, the main changes in the Mondego Estuary ecosystem (Portugal) were outlined, used as an illustrative example, and causes and effects described. Within the Mondego Estuary region the main water consumers are agriculture, industry, and households. Baseline scenarios predict an increase in water usage by mainly the touristic service sector. Our analysis illustrates that pressures from human population growth and related activities gradually increased over the studied period. Land-use patterns, diversion of freshwater flows, water pollution and morphological interventions directly caused physical, chemical, and biological modification and degradation. This consequently led to negative ecological and socio-economic impacts, such as eutrophication. The scenarios suggest an increased pressure based on an expected 8% annual population growth and an average annual decreased pressure of 5.2% per annum due to the current reduction in agriculture. The results show that understanding the water use-related complex and intricate trade-offs among ecological, social, and economic goals is fundamental in designing and implementing management policies and ecosystems restoration schemes.
► Main estuarine water services and uses provision considering ecological status. ► The DPSIR (driver, pressure, state, impact, response) framework as a helpful technical tool. ► Further steps to be undertaken aiming at an estuarine sustainable use.
The primary motivation of this work was the enhanced oil recovery in porous media. Polymeric solutions are largely used in tertiary oil recovery and it is of great interest to understand the role ...played by their properties in the recovery process. It is largely accepted that these solutions can increase the recovery efficiency compared to the water-flooding operation, but some doubts still remain. When polymers are added to a solvent, the viscosity of the mixing increases, and the solution becomes non-Newtonian, exhibiting shear-thinning behaviour and viscoelasticity. Thus, conducting tests that isolate all important parameters is not easy, and this is the goal here. A compact sand porous media was used, which was previously saturated with oil-based solutions. Such oil was recovered by the injection of Newtonian water-based or viscoelastic solutions. Diluted polyethylene oxide solutions, with concentration much lower than ten times the overlap concentration, were used. Below such concentration, elastic turbulence is not observed, and the so-called Saffman–Taylor problem is the main point here. The primary data are the fraction of unrecovered mass
m
until the displacing fluid breakthrough. The lost mass
m
was recorded as a function of the capillary number Ca, viscosity ratio
R
μ
, and Weissenberg number
Wi
. It was shown that for the cases evaluated in this work, the capillary effects were negligible, and therefore,
R
μ
and
Wi
were the only parameters that control the flow behaviour. For the Newtonian scenario, the not recovered mass
m
felt from 77.5%, for
R
μ
=
41.82
, to 20%, for
R
μ
=
0.52
, leading to an increase in the recovery ratio of 57.5%. For a fixed viscosity ratio,
m
felt with
Wi
until reaching an asymptotic value. For
R
μ
=
1
, the increase of
Wi
from
W
i
=
0.49
to
W
i
≥
5
leads to an increase in the recovery ratio of 35%, showing that more elastic fluids can improve the efficiency of the process.
The aim of the present study was to test whether different degrees of human activity affect the diet of the Brazilian silverside Atherinella brasiliensis in two tropical estuaries. Fish were ...collected along the salinity gradient of two Brazilian estuaries, the heavily impacted Paraiba Estuary and the less impacted Mamanguape Estuary, in the dry and wet seasons. The findings confirm that A. brasiliensis has generalist feeding habits and is able to change its diet under different environmental conditions. The results indicate clear spatial (i.e. along the estuarine gradient) changes in diet composition in both estuaries, but diet was also influenced by the degree of anthropogenic disturbance. During the wet season in the nutrient enriched Paraiba Estuary, when human activity was higher, the diet of A. brasiliensis was poorer and dominated by few dietary items, reflecting the potential impoverishment of prey items in this heavily disturbed system. The specimens collected in the most affected estuary also had a greater frequency of micro‐plastics and parasites in their stomachs, reflecting the greater degree of human disturbance in the estuary. The present findings suggest that the diet of A. brasiliensis could be a useful indicator of changes in the ecological quality of these and other tropical estuaries of the western Atlantic Ocean.
Mining sites are vulnerable to erosion and siltation of rivers. While the construction of rockfill dikes can mitigate siltation, existing rockfill dikes are typically constructed with natural ...aggregates, whose mining, beneficiation, and transportation entail additional adverse impacts. In this paper, ferronickel slag (FNS) was investigated as a free-draining rockfill dike material to be used in nearby mining sites. A series of laboratory tests, including physical, environmental, durability, chemical and mineralogical analyzes, was executed to evaluate the engineering characteristics of this byproduct and its potential use in dikes. Results demonstrate that FNS is non-uniform with relatively low Los Angeles abrasion. Leaching and dissolution tests have not shown harm to the environment since the average concentrations of chemical elements existing in FNS were below the standard requirements. Accelerated weathering cycling tests with ethylene glycol further highlighted that the byproduct does not suffer premature disaggregation in the presence of water, thereby revealing that the material can be employed adequately under saturated condition. Findings suggest that the use of FNS in rockfill dikes represents a technically and environmentally feasible solution, while reducing the use of natural aggregates, avoiding the formation of stockpiles, preventing siltation in downstream fluvial networks and other adverse impacts.
The use of industrial byproducts as replacement of natural aggregates has been extensively investigated to design eco-friendly roads. One of the most examined byproducts for this purpose is steel ...slag. However, existing studies do not explore the blending of different slags to enhance the engineering performance of base layers. The applicability of Linz–Donawitz (LD), Blast Furnace (BF) and Kambara Reactor (KR) steel byproducts is evaluated as a single base layer for rural (unsurfaced) roads in Brazil. A series of laboratory experiments were performed to assess the characteristics of eight soil-byproduct mixtures with 50% and 75% byproduct contents, including new blends of LD/KR and BF/KR slags. Additionally, the most suitable mixture was proposed considering different performance indicators. Results demonstrate the coarse-grained, nonplastic and non-expansive nature of the byproducts, with CBR values higher than 100%. The more byproduct added to soil, the larger is the strength and the lower the expansion. The mixture with 75% of the proposed LD/KR blend and 25% of a clayey soil was considered as optimum, based on a trade-off between engineering properties, environmental impacts, and material costs. Findings and discussions are relevant to reduce waste stockpiles of steel companies, helping engineers and policy makers reuse blended slag byproducts.
The injection of a fluid to displace another fluid is a very common process used to enhance the recovery factor in oil reservoirs. In circumstances where gravitational segregation and inertial forces ...are negligible and the capillarity number is high, the viscosity ratio is the only parameter that governs the flow. The main contribution of this study is the verification of the applicability of a simple equation to predict the effects of viscosity ratio on the residual oil mass that is kept trapped into the porous media, also called lost mass. The experiments, together with data from the literature, allowed us to evaluate the accuracy of the proposed equation. The simulations use an homogeneous representation of the porous media, since the heterogeneous representation is usually limited to micro-scale problems due to its high computational cost. Despite the limitations of the homogeneous model, it succeeded in predicting the flow patterns and the lost mass values for all the viscosity range evaluated except for viscosity ratio values smaller than one because, for this condition, the flow tends to the stable displacement pattern and, in this case, the adhesive forces of the oil with the grains that comprise the porous media must be considered.
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