Morphodynamics drive the transport and accumulation of anthropogenic microparticles in tropical coastal depositional systems in southeastern Brazil.

A significant limitation in current coastal pollution research is that microplastics (<5 mm) comprise only a fraction of all anthropogenic microparticles (AMP, <5 mm) scale residues. Comprehensive AMP assessments, including those comprising semisynthetic, and modified natural compositions, are lacking. For instance, the accumulation of AMP in different coastal morphological features within a depositional system remains poorly known, fueling long-lasting debates about the distribution process of microparticles.

Origin of sandy substrates controlling the distribution of open vegetation ecosystems in Amazonia.

Understanding the role of open vegetation, particularly in white-sand ecosystems (WSE) and savannas, is crucial for elucidating their role in Amazonian biotic diversification. These ecosystems predominantly develop on sandy terrains, suggesting that the geological substrate significantly influences the vegetation upon it. Therefore, the interaction between landscape changes and biotic diversification is closely tied to the dynamics and resilience of these sandy substrates.

Operational effects on aquatic carbon dioxide and methane emissions from the Belo Monte hydropower plant in the Xingu River, eastern Amazonia.

Operational demands and the natural inflow of water actively drive biweekly fluctuations in water levels in hydropower reservoirs. These daily to weekly fluctuations could have major effects on methane (CH) and carbon dioxide (CO) emissions via release of bubbles from reservoir bottom sediments (ebullition) or organic matter inputs, respectively. The impact of transient fluctuations in water levels on GHG emissions is poorly understood and particularly so in tropical run-of-the-river reservoirs.

Late Pleistocene landscape changes and habitat specialization as promoters of population genomic divergence in Amazonian floodplain birds.

Although vicariant processes are expected to leave similar genomic signatures among codistributed taxa, ecological traits such as habitat and stratum can influence genetic divergence within species. Here, we combined landscape history and habitat specialization to understand the historical and ecological factors responsible for current levels of genetic divergence in three species of birds specialized in seasonally flooded habitats in muddy rivers and which are widespread in the Amazon basin but have isolated populations in the Rio Branco. Populations of the white-bellied spinetail (Mazaria propinqua), lesser wagtail-tyrant (Stigmatura napensis) and bicolored conebill (Conirostrum bicolor) are currently isolated in the Rio Branco by the black-waters of the lower Rio Negro, offering a unique opportunity to test the effect of river colour as a barrier to gene flow.

South American precipitation dipole forced by interhemispheric temperature gradient.

Tropical South American hydroclimate sustains the world's highest biodiversity and hundreds of millions of people. Whitin this region, Amazonia and northeastern Brazil have attracted much attention due to their high biological and social vulnerabilities to climate change (i.e.

Phylogeography of Baryancistrus xanthellus (Siluriformes: Loricariidae), a rheophilic catfish endemic to the Xingu River basin in eastern Amazonia.

Baryancistrus xanthellus (Loricariidae) is an endemic fish species from the Xingu River basin with its life history in the shallow rapid waters flowing over bedrock substrates. In order to investigate the genetic diversity and demographic history of B. xanthellus we analyzed sequence data for one mitochondrial gene (Cyt b) and introns 1 and 5 of nuclear genes Prolactin (Prl) and Ribosomal Protein L3 (RPL3).

Microplastics in sediments from Amazon rivers, Brazil.

We assessed the concentrations of microplastics in sediment samples collected in seven sites from Solimões, Negro and Amazon rivers, upstream and downstream the metropolitan region of Manaus. Concentrations ranged from 417 to 8178 particles/kg of dried sediment (microplastics: 0.063-5 mm), and from 0 to 5725 particles/kg of dried sediment (microplastics: 0.

Shut down of the South American summer monsoon during the penultimate glacial.

We analysed changes in mean annual air temperature (MAAT), vegetation and biomass burning on a long and continuous lake-peat sediment record from the Colônia basin, southeastern Brazil, examining the responses of a wet tropical rainforest over the last 180 ka. Stronger southern atmospheric circulation up to the latitude of Colônia was found for the penultimate glacial with lower temperatures than during the last glacial, while strengthening of the South American summer monsoon (SASM) circulation started during the last interglacial and progressively enhanced a longer wet summer season from 95 ka until the present. Past MAAT variations and fire history were possibly modulated by eccentricity, although with signatures which differ in average and in amplitude between the last 180 ka.

Quaternary climate changes as speciation drivers in the Amazon floodplains.

The role of climate as a speciation driver in the Amazon has long been discussed. Phylogeographic studies have failed to recover synchronous demographic responses across taxa, although recent evidence supports the interaction between rivers and climate in promoting speciation. Most studies, however, are biased toward upland forest organisms, while other habitats are poorly explored and could hold valuable information about major historical processes.

Optically Stimulated Luminescence Sensitivity of Quartz for Provenance Analysis.

Finding the source or provenance of quartz grains occurring in a specific location allows us to constrain their transport pathway, which is crucial information to solve diverse problems in geosciences and related fields. The optically stimulated luminescence (OSL) sensitivity (light intensity per unit mass per unit radiation dose) has a high capacity for discrimination of quartz sediment grains and represents a promising technique for provenance analysis. In this study, we tested the use of quartz OSL sensitivity (ultraviolet emission) measured under different preheating temperatures and with blue light stimulation at room temperature (~20 °C) for sediment provenance analysis.

Equatorial Pacific forcing of western Amazonian precipitation during Heinrich Stadial 1.

Abundant hydroclimatic evidence from western Amazonia and the adjacent Andes documents wet conditions during Heinrich Stadial 1 (HS1, 18-15 ka), a cold period in the high latitudes of the North Atlantic. This precipitation anomaly was attributed to a strengthening of the South American summer monsoon due to a change in the Atlantic interhemispheric sea surface temperature (SST) gradient. However, the physical viability of this mechanism has never been rigorously tested.

Oxidative mitigation of aquatic methane emissions in large Amazonian rivers.

The flux of methane (CH4 ) from inland waters to the atmosphere has a profound impact on global atmospheric greenhouse gas (GHG) levels, and yet, strikingly little is known about the dynamics controlling sources and sinks of CH4 in the aquatic setting. Here, we examine the cycling and flux of CH4 in six large rivers in the Amazon basin, including the Amazon River. Based on stable isotopic mass balances of CH4 , inputs and outputs to the water column were estimated.

New Archaeological Evidence for an Early Human Presence at Monte Verde, Chile.

Questions surrounding the chronology, place, and character of the initial human colonization of the Americas are a long-standing focus of debate. Interdisciplinary debate continues over the timing of entry, the rapidity and direction of dispersion, the variety of human responses to diverse habitats, the criteria for evaluating the validity of early sites, and the differences and similarities between colonization in North and South America. Despite recent advances in our understanding of these issues, archaeology still faces challenges in defining interdisciplinary research problems, assessing the reliability of the data, and applying new interpretative models.

Methane emissions from Amazonian Rivers and their contribution to the global methane budget.

Methane (CH4 ) fluxes from world rivers are still poorly constrained, with measurements restricted mainly to temperate climates. Additional river flux measurements, including spatio-temporal studies, are important to refine extrapolations. Here we assess the spatio-temporal variability of CH4 fluxes from the Amazon and its main tributaries, the Negro, Solimões, Madeira, Tapajós, Xingu, and Pará Rivers, based on direct measurements using floating chambers.