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In seasonal tropical regions, rainfall and/or temporary floods during the wet season generally increase the abundance and diversity of food resources to many consumers as compared to the dry season. Therefore, seasonality can affect intraspecific competition and ecological opportunity, which are two important ecological mechanisms underlying population and individual niche variations. Here, we took advantage of the strong seasonality in the Pantanal wetlands to investigate how within-and between-individual diet variations relate to seasonal population niche dynamics of the tetra fish Astyanax lacustris. We quantified dietary niche using gut contents and stable isotopes. Tetras had higher gut fullness and better body condition in the wet season, suggesting that competition is more intense in the dry season. The population niche was broader in the wet season due to an increase in diet divergence between individuals, in spite of potential stronger competition in the dry season. We posit that low ecological opportunity in the dry season limits the diversifying effect of intraspecific competition, constraining population niche expansion. Our results add new insights on how seasonality affects population and individual diets, indicating that intraspecific competition and ecological opportunity interact to determine temporal niche variations in seasonal environments.

Land-use conversion from forest-to-pasture in the Amazon can affect soil physical quality and hydraulic functioning. The study evaluates the effects of land use (forest and pasture) and soil texture (fine and coarse) on soil structure and hydraulic properties, using the soil water retention curve as an integrative indicator. The study was conducted with soil samples from the Tapajós National Forest region, Pará State, Brazil, with eight sites (four forest and four pasture), balanced by texture. Undisturbed samples were collected from five profile layers (0–10, 10–20, 20–30, and 30–40 cm) for each site, totaling 160 samples. Samples were saturated and measured at soil water matric potentials from −0.1 to −15,000 hPa to obtain the soil water retention curve, which was fitted using the van Genuchten–Mualem model. Pore size distribution was derived from the relationship between soil water matric potential and equivalent pore diameter. Results are reported for the 0–40 cm soil profile (integrating the four sampled layers). Forest-to-pasture conversion altered soil pore structure and water retention in a texture-dependent manner. For fine-textured soils, bulk density increased from 1.03 to 1.31 Mg m−3 (+27%) from forest to pasture. In coarse-textured soils, the drainable pore volume up to −15,000 hPa, equivalent diameter > 0.2 µm) decreased from 0.296 to 0.147 m3 m−3 (−50%) from forest to pasture. Plant-available water across the 0–40 cm profile ranged from 0.107 m3 m−3 (pasture, fine-textured) to 0.137 m3 m−3 (forest, coarse-textured). Coarse-textured soils showed a marked reduction in macroporosity, water retention, and plant-available water, whereas fine-texture soils showed smaller changes in water availability but reduced aeration associated with macropore reduction. These results indicate higher physical quality vulnerability of coarse-textured soils following forest-to-pasture conversion.

Deforestation and land use change (LUC) to expand the agricultural frontier in the Brazilian Amazon deplete soil carbon (C) stocks, and negatively impact climate regulation. The variety of soil types, land-transition options, and management practices present in the Amazon region require detailed inventories to reduce the uncertainties associated with estimates of soil C change. Therefore, we conducted a study covering ca. 1 million hectares to estimate the soil C stock changes due to LUC in Paragominas and Santarém, Pará state, eastern Brazilian Amazon, for the period of 1990–2010. Soil C stocks for 1990 were modeled based on land cover at the time. In 2010, we carried out a field work taking soil samples to measure soil C stock changes in 356 transects across contrasting land uses (logged and burnt forest, young secondary forest, intermediate secondary forest, old secondary forest, pasture, and cropland). The response ratios for the conversion from undisturbed forest to new land uses were calculated considering the differences in soil C stocks, with the undisturbed forest as reference. Between 1990 and 2010, LUC induced a total loss of 1.51 Tg C year-1 (over an area of 7350 km2). For this period, the uncertainty of estimates was ± 23.2%. The land transitions to pasture and cropland were the main drivers of soil C losses. Thus, deforestation contributes to climate change not only through losses of forest biomass but also subsequently soil C losses. These results can inform national and international climate change initiatives associated with LUC in the eastern Brazilian Amazon.

Extreme climatic events may be translated into a higher frequency of both dry and wet years. Frequent droughts pose a challenge to water supply in terms of both quantity and quality. In order to cope with this, there has to be a documentation on the concentration of chemicals in water during such events. The southeast region of Brazil experienced a major drought event in 2014 leading to number of social, economic, and environmental impacts. The objective of the present paper is to understand the effect of an extreme drought on dissolved organic and inorganic carbon concentrations of the Piracicabal river, which is under high human pressure. Concentrations of both dissolved organic (DOC) and inorganic carbon (DIC) were monitored daily, for 30 days, during a dry month in 2014. DOC values found here were at least twice those observed in the river in non-extreme conditions. Rain events within this drought led to significant differences in discharge, DOC, and DIC. We built a dilution-concentration model which described an exponential relationship between discharge and both carbon forms. This indicated that drastic changes in concentrations of DOC and DIC are expected during such events. Our results may also apply to a number of regions in the world especially those of the developing countries where rivers are highly subjected to sewage impact.

The focus of this study was to investigate the wide use of Eucalyptus spp., an exotic plant with high allelopathic ability, in the reforestation programs of urban parks in São Paulo City, Brazil, over the last century. To understand the implications of using Eucalyptus spp. in the city’s parks, this study aimed to compare nutrient cycling and litter decomposition between a mixed composition of litter (i.e., native and exotic species) and the litter of a single species (i.e., Eucalyptus). To accomplish this, newly deciduous leaves were collected from two native and two exotic species that are commonly used in the afforestation of São Paulo as well as from Eucalyptus spp. The mixed composition of litter yielded a higher dry mass loss and return of macro- and micronutrients to the forest floor. The decomposition constant (k) values were 0.00322 and 0.00207 g g−1 day−1 for the mixed composition and Eucalyptus spp., respectively. The time required for decomposition of 50 and 95% of deciduous material was 215 and 931 days, respectively, and for the mixed litterfall 334 and 1449 days, respectively, for Eucalyptus spp. Therefore, the mixed litter exhibited greater dry mass loss and nutrient cycling in an urban forest of São Paulo City, since dry mass losses as well as speed and amount of nutrients returned to the forest floor were relatively higher compared to Eucalyptus spp. Nutrient cycling via Eucalyptus spp. litter was less efficient than mixed composition of litter, demonstrating that reforestation programs carried out in the twentieth century using only one species may have had little success. The results of this work emphasize the fact that in urban reforestation programs the City of São Paulo must consider the environmental and biogeographic characteristics of the species employed and use high levels of biodiversity, since the city lies in a megadiverse biome.

This study evaluates the consistency and validity of the data generated by the citizen science program Observando os Rios (OoR), coordinated by the SOS Mata Atlântica Foundation and active in 17 Brazilian states. Water quality index (WQI) results produced by OoR were compared with those of São Paulo’s environmental agency, Companhia Ambiental do Estado de São Paulo (CETESB), across three hydrographic mesobasins—Alto Tietê, Sorocaba/Médio Tietê, and Piracicaba–Capivari–Jundiaí (PCJ)—from 2002 to 2023. Methodological conversions were applied to harmonize OoR classifications with CETESB standards. Among them, the weighted model (OoR_CET_8*), which adjusts both parameter inclusion and weighting, showed the closest quantitative alignment with CETESB according to Welch’s t-tests. Exact agreement between OoR and CETESB classifications varied—90% in Alto Tietê, 10% in Sorocaba/Médio Tietê, and 65% in PCJ—while ±1-category agreement exceeded 95% in all regions, indicating strong qualitative coherence. Kappa coefficients confirmed substantial agreement in Alto Tietê (0.74), moderate agreement in Sorocaba/Médio Tietê (0.51), and moderate to substantial agreement in PCJ (0.58). Along the Tietê River, finer-scale analyses revealed marked spatial variability, with an average Kappa of 0.43 and reduced convergence in highly urbanized stretches such as Guarulhos and São Paulo, where OoR frequently assigned as “Regular” while CETESB classified the same sites as “Poor” or “Terrible.” This discrepancy reflects the broader amplitude of the Regular category in the OoR index (~32% of the scale), which can smooth short-term deterioration. Despite limitations associated with biological indicators and observer-dependent variability, OoR demonstrated robustness, broad spatial coverage, and strong socio-environmental relevance. With continued methodological refinement and deeper institutional integration, the program constitutes a scalable and replicable model for citizen-science-based water quality monitoring, particularly valuable in regions with limited governmental oversight.

The effects of cage aquaculture on freshwater ecosystems are determined by multiple farming and environmental variables, and thus, the assessment of a wide range of abiotic and biotic variables enables better understanding of the impacts generated by this nutrient source. This study was carried out at Castanhão reservoir located in the State of Ceará, which is the largest Brazilian producer of Nile tilapia in cage systems, wherein about 8000 reservoirs provide a vast area to expand not only this important socio-economic but also pollution-prone activity. Nutrient mass budget, water quality monitoring, hydrodynamic characterization, and elemental/stable isotopic composition of end-member products were measured in cage aquaculture and other reservoir areas in order to determine the relative effects on reservoir conditions. Nutrient budgets showed that 34 % of the artificial feed was lost to the water column but water quality monitoring and isotopic composition analysis suggested that the cages were not extensively impacting the water quality probably because of the physiographic and hydrodynamic features of the cage site.

São Paulo state, Brazil, is one of the main areas of sugar cane agriculture in the world. Herbicides, in particular, ametryn, are extensively used in this extensive area, which implies that this herbicide is present in the environment and can contaminate the surface water by running off. Thereby, residues of ametryn were analyzed in samples of river water an river sediment and in freshwater bivalves obtained from the rivers Sapucaí, Pardo and Mogi-Guaçu in São Paulo State, Brazil. Samples were taken in the winter of 2003 and 2004 in two locations in each river. The specimens of freshwater bivalves collected and analyzed were Corbicula fluminea , an exotic species, and Diplodon fontaineanus , a native species. Additionally, the evaluation of the ability of bioconcentration and depuration of ametryn by the freshwater bivalve Corbicula fluminea was also performed. Ametryn concentrations in the samples were measured by liquid chromatography coupled to mass spectrometry. Residues of ametryn in water (50 ng/L) and in freshwater bivalves (2–7 ng/g) were found in the Mogi-Guaçu River in 2004, and residues in river sediments were found in all rivers in 2003 and 2004 (0.5–2 ng/g). The observation of the aquatic environment through the analysis of these matrixes, water, sediment, and bivalves, revealed the importance of the river sediment in the accumulation of the herbicide ametryn, which can contaminate the biota.

The growth of urban centers, along with the fragmentation of natural habitats, can interfere with the distribution pattern of species and their abundance, thus compromising the conservation of urban biodiversity. Principal players in this biodiversity are arthropods that help to decompose litterfall, favoring the recycling of nutrients and, hence, are an important part in sustaining the forest fragments that remain in urban areas. Therefore, it is important to study arthropod biodiversity in green urban areas, especially those areas where litterfall management is an important part of maintaining biodiversity. Accordingly, this study evaluated arthropod diversity associated with litterfall in three urban forests with different size and litterfall management practices, including Água Branca Park (ABP) and Tietê Ecological Park (TEP)—Núcleo Engenheiro Goulart in São Paulo City and Chico Mendes Park (CMP) in Osasco City, all belonging to the Metropolitan Region of São Paulo (MRSP), Brazil. Four litterfall harvests were carried out in each park between April and August of 2015 with twelve samples collected with a wood mold (30-cmx30-cm) at randomly points on the forest floor. The collected material was then screened in the laboratory and the arthropods were visually separated and preserved in alcohol 70%. Arthropods were classified by the order to which they belonged. Litterfall was dried in a forced air oven at 65 °C for seven days. Dried litterfall was then separated into leaves, branches, reproductive parts and miscellaneous fragments and weighed. Arthropod diversity was measured by Shannon, Margalef and Pielou indexes and non-metric multidimensional scaling analysis (NMDS) using the Manhattan distance index. Litterfall weight was compared by one-way ANOVA. The orders Hymenoptera, Collembola and Isopoda were dominant in CMP, ABP and TEP, respectively but multiple rare orders had a presence in all parks, albeit at different abundance. NMDS showed abundance similarity among the parks; however, TEP showed greater richness, Shannon diversity and evenness. The fractions of leaf litterfall and reproductive parts were different between the CMP and TEP. Overall, our results confirm that neither litterfall management, nor park size, is a final determinant of arthropod distribution, even though the abundance of dominant species was shown to differ in each park.

Vehicular emissions comprise a main source of air pollutants, especially particulate matter (PM), which contains toxic compounds. Brazil has been restricting vehicular emissions for more than 30 years to minimize the impacts of fleet vehicles, but despite the restrictive legislation, several Brazilian cities still suffer from the effects of atmospheric pollution. The adoption of nature-based solutions (NbS) is being hailed as a sound alternative for improving urban air quality. In this sense, trees are a true reflection of the NbS concept since they can directly decrease PM levels by intercepting and resuspending particles, as well as altering pollution dispersion patterns. We wanted to understand the practical outcome of urban forest fragments as an NbS. Therefore, using litterfall in urban forest fragments, this study reported the role of green areas in reducing air pollution concentrations in 4 urban parks in Sao Paulo Megacity, Brazil. Air contaminants (Cd, Cu and Pb) varied from the edge to the core of urban forests. Multivariate analysis revealed that areas with different vehicle fleets influenced the input of air pollutants into these forest fragments. Our study further showed that trees serve as a natural barrier against PM. It can be concluded that this low-cost NbS alternative can reduce air pollution and has a potential to improve human health and well-being, and should be incorporated into municipal policies and programs, especially in critical locations of high human density. and poorly managed green areas.