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Natural and Anthropogenically Influenced Isoprene Oxidation in Southeastern United States and Central Amazon
No full textAnthropogenic emissions alter secondary organic aerosol (SOA) formation chemistry from naturally emitted isoprene. We use correlations of tracers and tracer ratios to provide new perspectives on sulfate, NOx, and particle acidity influencing isoprene-derived SOA in two isoprene-rich forested environments representing clean to polluted conditions-wet and dry seasons in central Amazonia and Southeastern U.S. summer. We used a semivolatile thermal desorption aerosol gas chromatograph (SV-TAG) and filter samplers to measure SOA tracers indicative of isoprene/HO2 (2-methyltetrols, C5-alkene triols, 2-methyltetrol organosulfates) and isoprene/NOx (2-methylglyceric acid, 2-methylglyceric acid organosulfate) pathways. Summed concentrations of these tracers correlated with particulate sulfate spanning three orders of magnitude, suggesting that 1 μg m-3 reduction in sulfate corresponds with at least âˆ0.5 μg m-3 reduction in isoprene-derived SOA. We also find that isoprene/NOx pathway SOA mass primarily comprises organosulfates, âˆ97% in the Amazon and âˆ55% in Southeastern United States. We infer under natural conditions in high isoprene emission regions that preindustrial aerosol sulfate was almost exclusively isoprene-derived organosulfates, which are traditionally thought of as representative of an anthropogenic influence. We further report the first field observations showing that particle acidity correlates positively with 2-methylglyceric acid partitioning to the gas phase and negatively with the ratio of 2-methyltetrols to C5-alkene triols. © 2020 American Chemical Society
Impact of biomass burning on a metropolitan area in the Amazon during the 2015 El Niño: The enhancement of carbon monoxide and levoglucosan concentrations
No full textBiomass burning emissions in the Amazon caused a substantial degradation in the air quality of the Manaus Metropolitan Region (MMR) during the El Niño event of 2015. © 2020 Elsevier LtdExtreme droughts associated with changes in the climate have occurred every 5 years in the Amazon during the 21st century, with the most severe being in 2015. The increase in biomass burning (BB) events that occurred during the 2015 drought had several negative socioeconomic and environmental impacts, one of which was a decrease in the air quality. This study is an investigation into the air quality in the Manaus Metropolitan Region (MMR) (central Amazon, Brazil) during the dry (September to October) and wet (April to May) seasons of 2015 and 2016. A strong El Niño event began during the wet season of 2015 and ended during the wet season of 2016. Particulate matter samples were collected in the MMR during 2015 and 2016, and analyses of the satellite-estimated total carbon monoxide (CO) column and observed levoglucosan concentrations were carried out. Levoglucosan has been shown to be significantly correlated with regional fires and is a well-established chemical tracer for the atmospheric particulates emitted by BB, and CO can be treated as a gaseous-phase tracer for BB. The number of BB events increased significantly during the El Niño period when compared to the average number during 2003–2016. Consequently, the total CO column and levoglucosan concentration values in the MMR increased by 15% and 500%, respectively, when compared to the normal conditions. These results indicate that during the period that was analyzed, the impacts of BB were exacerbated during the strong El Niño event as compared to the non-El Niño period. In this study, we provided evidence that the air quality in the MMR will degrade in the future if droughts and BB occurrences continue to increase. © 2020 Elsevier Lt
Centric fusions behind the karyotype evolution of neotropical nannostomus pencilfishes (Characiforme, Lebiasinidae): First insights from a molecular cytogenetic perspective
Full text linkLebiasinidae is a Neotropical freshwater family widely distributed throughout South and Central America. Due to their often very small body size, Lebiasinidae species are cytogenetically challenging and hence largely underexplored. However, the available but limited karyotype data already suggested a high interspecific variability in the diploid chromosome number (2n), which is pronounced in the speciose genus Nannostomus, a popular taxon in ornamental fish trade due to its remarkable body coloration. Aiming to more deeply examine the karyotype diversification in Nannostomus, we combined conventional cytogenetics (Giemsa-staining and C-banding) with the chromosomal mapping of tandemly repeated 5S and 18S rDNA clusters and with interspecific comparative genomic hybridization (CGH) to investigate genomes of four representative Nannostomus species: N. beckfordi, N. eques, N. marginatus, and N. unifasciatus. Our data showed a remarkable variability in 2n, ranging from 2n = 22 in N. unifasciatus (karyotype composed exclusively of metacentrics/submetacentrics) to 2n = 44 in N. beckfordi (karyotype composed entirely of acrocentrics). On the other hand, patterns of 18S and 5S rDNA distribution in the analyzed karyotypes remained rather conservative, with only two 18S and two to four 5S rDNA sites. In view of the mostly unchanged number of chromosome arms (FN = 44) in all but one species (N. eques; FN = 36), and with respect to the current phylogenetic hypothesis, we propose Robertsonian translocations to be a significant contributor to the karyotype differentiation in (at least herein studied) Nannostomus species. Interspecific comparative genome hybridization (CGH) using whole genomic DNAs mapped against the chromosome background of N. beckfordi found a moderate divergence in the repetitive DNA content among the species’ genomes. Collectively, our data suggest that the karyotype differentiation in Nannostomus has been largely driven by major structural rearrangements, accompanied by only low to moderate dynamics of repetitive DNA at the sub-chromosomal level. Possible mechanisms and factors behind the elevated tolerance to such a rate of karyotype change in Nannostomus are discussed. © 2020 by the authors. Licensee MDPI, Basel, Switzerland
Water diversion in Brazil threatens biodiversity
No full textConstruction of water diversions is a common response to the increasing demands for freshwater, often resulting in benefits to communities but with the risk of multiple environmental, economic, and social impacts. Water-diversion projects can favor massive introductions and accelerate biotic homogenization. This study provides empirical evidence on the consequences of a proposed law intended to divert water from two large and historically isolated river basins in Brazil: Tocantins to São Francisco. Compositional similarity (CS) and β-diversity were quantified encompassing aquatic organisms: mollusks, zooplankton, crustaceans, insects, fishes, amphibians, reptiles, mammals, and plants. For CS we (i) considered only native species, and (ii) simulated the introduction of non-natives and assumed the extinction of threatened species due to this water-diversion project. We highlight the environmental risks of such large-scale projects, which are expected to cause impacts on biodiversity linked to bioinvasion and homogenization, and we recommend alternatives in order to solve water-demand conflicts. © 2019, Royal Swedish Academy of Sciences
Predicting biodiversity loss in island and countryside ecosystems through the lens of taxonomic and functional biogeography
Full text linkWe investigate how variation in patch area and forest cover quantified for three different spatial scales (buffer size of 500, 1500 and 3000 m radius) affects species richness and functional diversity of bat assemblages in two ecosystems differing in fragment–matrix contrast: a landbridge island system in Panama and a countryside ecosystem in the Brazilian Amazon. Bats were sampled on 11 islands and the adjacent mainland in Panama, and in eight forest fragments and nearby continuous forest in Brazil. Species–area relationships (SAR) were assessed based on Chao1 species richness estimates, and functional diversity–area relationships (FAR) were quantified using Chao1 functional diversity estimates measured as the total branch length of a trait dendrogram. FARs were calculated using three trait sets: considering five species functional traits (FARALL), and trait subsets reflecting ‘diet breadth’ (FARDIET) and ‘dispersal ability’ (FARDISPERSAL). We found that in both study systems, FARALL was less sensitive to habitat loss than SAR, in the sense that an equal reduction in habitat loss led to a disproportionately smaller loss of functional diversity compared to species richness. However, the inhospitable and static aquatic matrix in the island ecosystem resulted in more pronounced species loss with increasing loss of habitat compared to the countryside ecosystem. Moreover, while we found a significant FARDISPERSAL for the island ecosystem in relation to forest cover within 500 m landscape buffers, FARDIET and FARDISPERSAL were not significant for the countryside ecosystem. Our findings highlight that species richness and functional diversity in island and countryside ecosystems scale fundamentally differently with habitat loss, and suggest that key bat ecological functions, such as pollination, seed dispersal and arthropod suppression, may be maintained in fragments despite a reduction in species richness. Our study reinforces the importance of increasing habitat availability for decreasing the chances of losing species richness in smaller fragments. © 2019 The Authors. Ecography published by John Wiley & Sons on behalf of Nordic Society Oiko
Hydrological processes interconnecting the two largest watersheds of South America from seasonal to intra-monthly time scales: A critical review
No full textMany articles on the subjects of moisture transport, precipitation and surface hydrology of the two largest watersheds of South America, the Amazon and the La Plata basins, are stitched together to obtain an overview of the aspects related to the hydrological processes interconnecting them on time scales ranging from seasonal to intra-monthly. In the mean, moisture from the tropical Atlantic Ocean is transported by the trade winds into the Amazon Basin. A good part of it precipitates over the Amazon Basin and the other part reaches the La Plata Basin by northerly winds east of the Andes. Besides the moisture transported from the Atlantic, there is evapotranspiration in the Amazon and La Plata basins. A part of the evapotranspiration of the Amazon Basin precipitates over the same basin, contributing with about 1/3 of annual precipitation this basin, and a part joins the aerial stream into the La Plata Basin, contributing with about 1/4 of its annual precipitation. Semi-permanent and transient meteorological systems such as Inter-Tropical Convergence Zone, South Atlantic Convergence Zone, Low-Level Jet (LLJ) east of the Andes, Madden–Julian Oscillation, cold fronts and cyclones play an important role in the seasonal and intra-seasonal variations of precipitation, evapotranspiration and river discharge. The hydrological memory in Amazonian soils and the LLJ constitute an inter-seasonal coupling between the water balances of the two basins. All these aspects are succinctly described and discussed in this review article. Hypotheses for future research are formulated. © 2020 Royal Meteorological Societ
The Avifauna of the Rio Branco, an Amazonian evolutionary and ecological hotspot in peril
No full textThe Rio Branco is a river with unique biogeographic and ecological features, threatened by the Brazilian Government's plan to build a major hydroelectric dam and associated hydroway along its course. The river crosses one of Amazonia's largest rainfall gradients and a major geomorphological boundary along a savanna/forest ecotone, marked by the Bem Querer rapids. Above the rapids, the upper Rio Branco runs through the Boa Vista sedimentary formation and crosses the crystalline rocks of the Guiana Shield, and its margins are flanked by gallery forests. Downriver, it runs through a low-lying sedimentary basin, with Amazonian floodplain forests along its margins. Here, we present the results of ∼ 15 years of ornithological research on the Branco and its major tributaries, providing baseline data and evaluating potential threats to the riverine avifauna. Our surveys included opportunistic observations and standardized surveys along the entire length of the river in 16 systematically distributed localities. We catalogued 439 bird species, 87% of which are documented by physical evidence (specimens, recordings, photographs). Forty-six percent are restricted to single habitats, suggesting a high degree of habitat specialisation. A third of the species are widely distributed along the river, whereas 45% are restricted to either the upper or the lower Rio Branco, including 40 and 30 Indicator Species, respectively. Twenty-five species are threatened at global or national levels, including two 'Critically Endangered', nine 'Vulnerable', and 14 'Near Threatened'. We present a list of 50 bird species that are candidates for monitoring studies. Threats to the avifauna from dam construction include permanent flooding above the dam, eliminating gallery forests, river islands, and sandy beaches, and the disruption of the flood pulse along the river, affecting river island and floodplain forest specialists, many of which are globally threatened with extinction. If built, the Bem Querer dam will wipe out the ecotone region and affect dramatically the river's avifauna. © BirdLife International 2019
Composição e estabilidade temporal de assembleias de peixes em igarapés de cabeceira na bacia do rio Xingu
Full text linkThe Amazon basin harbor to a complex system of small watercourses, known regionally as igarapés. These small streams are highly dependent on the availability of rain in their drainage areas, which makes them sensitive to the environmental changes taking place on the planet. Recent studies indicate that ichthyofauna amazonian presents a low resistance and resilience to climate change, being sensitive to abrupt climate changes, such as extreme and gradual droughts, such as increased precipitation and frequency of stormy. Faced with the fragility of this ichthyofauna and the climatic models that predict the increase in the frequency and intensity of extreme events, it is essential to identify the effects of these events on these assemblies in order to develop efficient conservation strategies. In this study, we verified whether there are differences in the composition of the fish assemblages of terra-firme perennial streams between periods of drought and rain, and we assessed the effects of the flow interruption caused by a severe drought on the ichthyofauna of 12 streams of terra-firme in the Xingu river basin, in the Brazilian East Amazon, between 2012 and 2014. At the end of the dry period of the first year of sampling, six streams dried up completely or were reduced to disconnected puddles of water. It was found that the fish assemblages of the perennial streams present stability in their structure over time, not differing between periods. On the other hand, the fish assemblages of the streams that dried up took on a new configuration after the temporary interruption of the flow. Most of the changes detected were transient, however, some persisted after the flow resumed. Together, these results indicate that severe drought events can change the composition of fish species in headwater streams and that such changes may persist in the medium term (years).A bacia amazônica abriga um complexo sistema de pequenos cursos d’água, conhecidos regionalmente como igarapés. Esses pequenos igarapés são altamente dependentes da disponibilidade de chuvas em suas áreas de drenagem, o que os tornam sensíveis às mudanças ambientais em curso no planeta. Estudos recentes indicam que a ictiofauna amazônica apresenta uma baixa resistência e resiliência às mudanças climáticas, sendo sensível a mudanças climáticas abruptas, como secas extremas, e graduais, como o aumento da precipitação e da frequência de tempestades. Diante da fragilidade dessa ictiofauna e dos modelos climáticos que preveem o aumento da frequência e intensidade de eventos extremos, torna-se fundamental identificar os efeitos desses eventos sobre essas assembleias para a elaboração de estratégias eficientes de conservação. Neste estudo, verificamos se existem diferenças na composição das assembleias de peixes de igarapés de terra firme perenes entre os períodos de seca e chuva, e avaliamos os efeitos da interrupção de fluxo causada por uma forte seca sobre a ictiofauna de 12 igarapés de terra firme da bacia do rio Xingu, na Amazônia Oriental brasileira, entre 2012 e 2014. No final do período seco do primeiro ano de amostragens, seis desses igarapés secaram completamente ou ficaram reduzidos a poças desconectadas. Verificou-se que as assembleias de peixes dos igarapés perenes apresentam estabilidade na sua estrutura ao longo do tempo, não diferindo entre os períodos de seca e chuva. Por outro lado, as assembleias de peixes dos igarapés que secaram tomaram uma nova configuração após a interrupção temporária do fluxo. A maioria das mudanças detectadas foram transitórias, no entanto, algumas persistiram após a retomada do fluxo. Em conjunto, esses resultados indicam que eventos de secas fortes podem alterar a composição de espécies de peixes de igarapés de cabeceira, e que tais mudanças podem persistir em médio prazo (anos)
Dissolved methane concentrations and fluxes to the atmosphere from a tropical floodplain lake
No full textLarge uncertainties in estimates of methane (CH4) emissions from tropical inland waters reflect the paucity of information at appropriate temporal and spatial scales. CH4 concentrations, diffusive and ebullitive fluxes, and environmental parameters in contrasting aquatic habitats of Lake Janauacá, an Amazon floodplain lake, measured for two years revealed patterns in temporal and spatial variability related to different aquatic habitats and environmental conditions. CH4 concentrations ranged from below detection to 96 µM, CH4 diffusive fluxes from below detection to 2342 µmol m−2 h−1, and CH4 ebullitive fluxes from 0 to 190 mmol m−2 d−1. Vegetated aquatic habitats had higher surface CH4 concentrations than open water habitats, and no significant differences in diffusive CH4 fluxes, likely due to higher k values measured in open water habitats. CH4 emissions were enhanced after a prolonged low water period, when the exposed sediments were colonized by herbaceous plants that decomposed after water levels rose, possibly fueling CH4 production. Statistical models indicated the importance of variables related to CH4 production (temperature, dissolved organic carbon) and consumption (dissolved nitrogen, oxygenated water column), as well as maximum depth, in controlling surface water CH4 concentrations. © 2020, Springer Nature Switzerland AG