The Pantanal natural region in South America is the largest wetland worldwide. Due to floods and a diverse lithology, this wetland area exhibits high plant and animal biodiversity levels and ...encompasses more than 185,000 km
2
. In 2020, the Pantanal experienced the worst recorded fire episode in history. Hundreds of thousands of hectares burned, threatening habitats and corresponding ecosystem functions. The fire reached regions never burned before, including national conservation units. Although federal authorities have blamed climate change and cultural indigenous practices, environmentalists, scientists, and non-governmental organizations have questioned this foregone conclusion. To better understand this historical event, we examined the burn severity in conservation units most affected by fire and the association with human and climate factors (represented by the fire occurrence distance to roads/waterways/railways and drought severity, respectively) and analyzed fire spatial patterns and durations. Via a comparison of these two factors, we demonstrated that 60% of the fire outbreaks was concentrated at distances less than 5 km from roads, waterways, and railways and that 80% was concentrated at distances less than 10 km from areas with human activities. Since values of the SPEI (drought index) < −2.6 were critical to the spread of fire, a combination of more favorable climate conditions enabled the rapid and irreversible spread of fire. The observed association between fire occurrence and distance to roads makes the ongoing plans for road expansion of great concern, considering the 2020 fire episode, which greatly affected natural vegetation and conservation units across the Pantanal. The determination of trends in fire hot spot regions in the Pantanal can help environmental surveillance and fire control.
Aerosols have implications to climate and biogeochemical cycles in the global oceans. At sites under indirect influence of dust emitted by the Patagonian semi-desert, a debate exists on the potential ...fertilization effects of iron enriched aerossol. Considering this subject we conducted measurements of aerosols optical properties using a Microtops II sun photometer to access aerosol size distributions and other intrinsic properties oversea from Atlantic Southern mid-latitudes to Antarctica. Oceanographic cruises were developed between December 2010 to April 2011 and October 2011 to April 2012, in the context of the Brazilian Antarctic Program, and between November 2011 to December 2011. This survey was taken as part of the Global Maritime Aerosol Network (MAN/NASA). Our data of AOD (500 nm) along the South American coast depicts a steady decrease southwards following the decreased latitudinal continental extent. However, the influence of the aerosols blown from Patagonia semi-desert region was clear from latitude 53⁰S to 64⁰S. The predominance of aerosol fine mode was observed in Central Atlantic and close to the Drake Passage. An unexpected aerosol coarse mode predominance was found close to the Antarctic Peninsula. We attribute that to a possible weathering of rock outcrops due to the strong westerly winds in that region.
The knowledge on the deposition and retention of the viral particle of SARS-CoV-2 in the respiratory tract during the very initial intake from the ambient air is of prime importance to understand the ...infectious process and COVID-19 initial symptoms. We propose to use a modified version of a widely tested lung deposition model developed by the ICRP, in the context of the ICRP Publication 66, that provides deposition patterns of microparticles in different lung compartments. In the model, we mimicked the "environmental decay" of the virus, determined by controlled experiments related to normal speeches, by the radionuclide 11C that presents comparable decay rates. Our results confirm clinical observations on the high virus retentions observed in the extrathoracic region and the lesser fraction on the alveolar section (in the order of 5), which may shed light on physiopathology of clinical events as well on the minimal inoculum required to establish infection.
The Amazon Basin is one of the most productive regions in the world and an important carbon sink. However, lake productivity has varied throughout the Holocene, as preserved in lacustrine sedimentary ...records. Concentrations of chlorophyll pigmented derivatives that are mainly derived from phytoplankton and macrophyte populations can be used to infer lake production levels. Here we use the chlorophyll derivatives concentrations analyzed by spectrophotometer in sediment cores from nine lakes distributed throughout the Brazilian Amazon Basin to document the continental-scale changes in lake production during the Holocene. Chlorophyll derivatives have varied with changes in precipitation rate throughout the last 10,000 years, similar to other climate records in tropical South America, including Ti concentration from the Cariaco Basin, δ13C from Lake Titicaca, and refractory black carbon in Nevado Illimani. Increasing precipitation is responsible for increasing the nutrient supply into the lake, which stimulates primary production. Our analysis was compared to climate-related parameters, suggesting an increasing trend of lake production rates during the wetter Late and Early Holocene, while lower production rates characterized the dry phase of the Middle Holocene. Therefore, the chlorophyll derivatives concentrations generally follow precipitation changes in the Amazon Basin during the Holocene.
It is estimated that the explosive Hudson volcano eruption in Southern Chile injected approximately 2.7 km3 of basalt and trachyandesite tephra into the troposphere between August 8-15, 1991. The ...Hudson signal has been detected in Antarctica at the eastern sector and in South Pole snow. In this work, we track the Hudson volcanic plume using a dispersion model, remote sensing, and a re-analysis of a high-resolution ice core analysis from the Detroit Plateau in the Antarctic Peninsula and sedimentary records from shallow lakes from King George Island (KGI). The Hudson eruption imprint in these records is confirmed by using a weekly resolved aerosol concentration database from KGI demonstrating that the regional impact of Hudson eruption predominates over the Mount Pinatubo/Phillippines volcanic signal, dated from June 1991, in terms of particulate matter depositions. The aerosol elemental composition of Ca, Fe, Ti, Si, Al, Zn, and Pb increases from 2 to 3 orders of magnitude in background level during the days following the eruption of the Hudson volcano.
Despite the extent use of geochemical tracers to track warm air mass origin reaching the Antarctic continent, we present here evidences that microorganisms being transported by the atmosphere and ...deposited in fresh snow layers of Antarctic ice sheets do act as tracers of air mass advection from the Southern Patagonia region to Northern Antarctic Peninsula. We combined atmospheric circulation data with microorganism content in snow/firn samples collected in two sites of the Antarctic Peninsula (King George Island/Wanda glacier and Detroit Plateau) by using flow cytometer quantification. In addition, we cultivated, isolated and submitted samples to molecular sequencing to precise species classification. Viable gram-positive bacteria were found and recovered in different snow/firn layers samples, among dead and living cells, their number concentration was compared to northern wind component, stable isotopes of oxygen, d18O, and the concentration of crustal elements (Fe, Ti and Ca). Use of satellite images combined with air mass back-trajectory analysis obtained from the NOAA/ HYSPLIT model corroborated the results.
Threats leading to a reduction in coral populations are apparent worldwide. Several different approaches have been tested to accelerate the adaptation of corals to a changing climate. Here, we ...evaluated the skeleton structure, crystal habit, and chemical changes of the coral
Pocillopora damicornis
in response to the pathogen (
Vibrio coralliilyticus
) and probiotic (Beneficial Microorganisms for Corals, BMCs) inoculation under ambient conditions (26 °C) and thermal stress (30 °C) during a 50-day mesocosm experiment. The skeletons were analyzed using microtomography, energy-dispersive x-ray spectroscopy (EDX/SEM), and densitometry to investigate the skeleto-physico-chemical micro-morphological changes in porosity, median pore-size diameter, crystal habit, Mg/Ca, Sr/Ca, the skeleton mineral density (g/cm
2
) and skeleton mineral content (g
–2
). The results indicate considerable changes in the coral skeleton caused by both temperature and microbial inoculation. Most importantly, lower density (to ∼ x̄ 0.5 g/cm
2
) and higher porosity (up to ∼ x̄ 47%) were correlated with inoculation of
V. coralliilyticus
and mitigated by probiotics. BMCs also substantially increased calcification, as evidenced by Mg/Ca in the skeleton of thermally stressed corals. At the micron scale, aragonite crystal fibbers precipitated during the experiments showed an acicular habit in thermally stressed and pathogen-inoculated corals kept at 30 °C. In contrast, a spherulitic habit, characteristic of high growth rates, was observed in corals inoculated with both BMCs and
V. coralliilyticus
. Our findings reveal that pathogen inoculation and thermal stress had notable impacts on coral skeleton properties, including porosity, density, and crystal morphology, in a short period of time, which highlights the potential impacts of shifts in climate warming and environmental quality. Interestingly, BMCs played a role in maintaining the properties of skeleton calcification.
A large amount of dust from the Sahara reaches the Amazon Basin, as observed with satellite imagery. This dust is thought to carry micronutrients that could help fertilize the rainforest. However, ...considering different atmospheric transport conditions, different aridity levels in South America and Africa and active volcanism, it is not clear if the same pathways for dust have occurred throughout the Holocene. Here we present analyses of Sr-Nd isotopic ratios of a lacustrine sediment core from remote Lake Pata in the Amazon region that encompasses the past 7,500 years before present, and compare these ratios to dust signatures from a variety of sources. We find that dust reaching the western Amazon region during the study period had diverse origins, including the Andean region and northern and southern Africa. We suggest that the Sahara Desert was not the dominant source of dust throughout the vast Amazon basin over the past 7,500 years.
Mineral dust deposited over the western Amazon region through the Holocene is not limited to a Saharan source and instead has diverse origins, according to geochemical fingerprinting of dust from lacustrine deposits.
Abstract
Since the early 1980s, the Antarctic environment has served as a natural field laboratory for researchers to investigate the effects of stratospheric ozone depletion, which has resulted in ...increased surface ultraviolet radiation levels. However, its effective threats still present gaps. We report new pieces of evidence of increased ultraviolet radiation impacting West Antarctica sea salt aerosols. Salt aerosols, particularly in the Southern Ocean Sea, play an important role in the radiative earth balance. To disclose the molecular details of sea salt aerosols, we used a synchrotron-based multi-element microscopic speciation of individual microparticles (Scanning Transmission X-ray Microscopy with Near-Edge X-ray Absorption Fine Structure Spectroscopy combined with Computer-Controlled Scanning Electron Microscopy). Here we identified substantial abundances of chlorine-enriched aerosols in sea salt generated by photolytic products, whereas ice core records revealed increased chlorine depletion from the onset of ozone depletion. Our findings reveal that modern sea salt modification has no Holocene precedent.
Ultraviolet (UV) radiation is the main exogenous inductor of skin damage and so photoprotection is important to control skin disorders. The Antarctic moss Sanionia uncinata is an important source of ...antioxidants and the photoprotective activity of its organic extracts has been investigated. This study aimed to evaluate the potential photoprotection, cytotoxicity and embryotoxicity of residual aqueous fraction (AF) from the moss S. uncinata.
UV-visible spectrum and SPF (sun protection factor) were determined by spectrophotometry. Embryotoxicity potential was evaluated by Fish embryo-larval toxicity test using zebrafish (Danio rerio) as organism model. Cell death assays by water-soluble tetrazolium salt (WST-1) and lactate dehydrogenase (LDH) were investigated using HaCaT keratinocyte cell line cultured in monolayers and three dimensions (3D). Phototoxicity and association with UV-filters were performed by 3T3 neutral red uptake test.
The AF showed sharp absorption bands in the UV region and less pronounced in the visible region. The SPF was low (2.5 ± 0.3), but the SPF values of benzophenone-3 and octyl-methoxycinnamate increased ~ 3 and 4 times more, respectively, in association with AF. The AF did not induce significant lethal and sublethal effects on zebrafish early-life stages. In monolayers, the HaCaT cell viability, evaluated by WST-1, was above 70% by ≤0.4 mg AF/mL after 48 and 72-h exposure, whereas ≤1 mg AF/mL after 24-h exposure. The LDH assay showed that the cell viability was above 70% by ≤0.4 mg AF/mL even after 72-h exposure, but ≤1 mg/mL after 24 and 48-h exposure. In 3D cell culture, an increased cell resistance to toxicity was observed, because cell viability of HaCaT cell by WST-1 and LDH was above ~ 90% when using ≤1 and 4 mg AF/mL, respectively. The AF demonstrated values of photo irritation factor < 2 and of photo effect < 0.1, even though in association with UV-filters.
The residual AF absorbs UV-vis spectrum, increased SPF values of BP-3 and OMC and does not induce embryotoxicity to zebrafish early life-stage. The cell death assays allowed establishing non-toxic doses of AF and phototoxicity was not detected. AF of S. uncinata presents a good potential for skin photoprotection against UV-radiation.
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