Biological nitrogen fixation (BNF) supports terrestrial primary productivity and plays key roles in mediating human-induced changes in global nitrogen (N) and carbon cycling. However, there are still ...critical uncertainties in our understanding of the amount of BNF occurring across terrestrial ecosystems, and of how terrestrial BNF will respond to global change. We synthesized BNF data from Latin America, a region reported to sustain some of the highest BNF rates on Earth, but that is underrepresented in previous data syntheses. We used meta-analysis and modeling approaches to estimate BNF rates across Latin America's major biomes and to evaluate the potential effects of increased N deposition and land-use change on these rates. Unmanaged tropical and subtropical moist forests sustained observed and predicted total BNF rates of 10 ± 1 and 14 ± 1 kg N ha−1 y−1, respectively, supporting the hypothesis that these forests sustain lower BNF rates than previously thought. Free-living BNF accounted for two-thirds of the total BNF in these forests. Despite an average 30% reduction of free-living BNF in response to experimental N-addition, our results suggest free-living BNF rate responses to current and projected N deposition across tropical and subtropical moist forests are small. In contrast, the conversion of unmanaged ecosystems to crop and pasture lands increased BNF rates across all terrestrial biomes, mostly in savannas, grasslands, and dry forests, increasing BNF rates 2-fold. The information obtained here provides a more comprehensive understanding of BNF patterns for Latin America.
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•How much biological nitrogen fixation (BNF) occurs in the biosphere is uncertain.•Latin America (LA) sustains high BNF but is underrepresented in previous syntheses.•We estimated BNF across LA using meta-analysis and modeling approaches.•Tropical moist forests in LA sustain lower BNF than previously thought.•The conversion of unmanaged to agriculture lands increased BNF up to 2-fold in LA.
Peatlands are carbon‐rich ecosystems that cover 185–423 million hectares (Mha) of the earth's surface. The majority of the world's peatlands are in temperate and boreal zones, whereas tropical ones ...cover only a total area of 90–170 Mha. However, there are still considerable uncertainties in C stock estimates as well as a lack of information about depth, bulk density and carbon accumulation rates. The incomplete data are notable especially in tropical peatlands located in South America, which are estimated to have the largest area of peatlands in the tropical zone. This paper displays the current state of knowledge surrounding tropical peatlands and their biophysical characteristics, distribution and carbon stock, role in the global climate, the impacts of direct human disturbances on carbon accumulation rates and greenhouse gas (GHG) emissions. Based on the new peat extension and depth data, we estimate that tropical peatlands store 152–288 Gt C, or about half of the global peatland emitted carbon. We discuss the knowledge gaps in research on distribution, depth, C stock and fluxes in these ecosystems which play an important role in the global carbon cycle and risk releasing large quantities of GHGs into the atmosphere (CO2 and CH4) when subjected to anthropogenic interferences (e.g., drainage and deforestation). Recent studies show that although climate change has an impact on the carbon fluxes of these ecosystems, the direct anthropogenic disturbance may play a greater role. The future of these systems as carbon sinks will depend on advancing current scientific knowledge and incorporating local understanding to support policies geared toward managing and conserving peatlands in vulnerable regions, such as the Amazon where recent records show increased forest fires and deforestation.
Tropical peatlands store 152–288 Gt of carbon, which is significantly higher than the previously reported values. The carbon accumulation rates in undisturbed tropical peatlands are generally much higher than in intact old‐growth tropical forests. Tropical disturbed peatlands have higher CO2 emissions than non‐disturbed peatlands due to the maintenance of natural soil moisture conditions and groundwater levels.
Abstract Changes in the physical and biogeochemical properties of water columns are frequently associated with cold fronts and mesoscale convective systems due to increased cloud cover. The effects ...of low-level jet (LLJ) events on thermal stratification and water quality, however, remain undescribed, particularly for tropical reservoirs. Here, water temperature time series are combined with meteorological data, LIDAR observations, ERA5 reanalysis data, and hydrodynamical modeling to investigate the impact of an event of LLJ over the Furnas hydropower reservoir in Brazil. The LLJ event was characterized by dry, intense, and persistent winds (~10 m s-1) blowing for more than 12 hours over the main fetch of the reservoir. In the downwind side of the lake, the surface mixed layer depth increased by 50% during the LLJ event. The changes to the water column were produced by a combination of wind-induced upwelling, shear-driven mixing, and nocturnal convective overturning, different from the heat balance expected during passing cold fronts and mesoscale convective systems. The results suggest that both momentum and heat fluxes during LLJ events need to be accounted for in lake modelings to reproduce the vertical mixing process.
•Functional traits described better human intervention than species identity.•Flow-regulation by river damming increased the functional nestedness of phytoplankton.•Species from dammed areas were ...filtered by the river flow after the dams.•Land use amplified the effects of river damming on the phytoplankton community.
River damming reduces the dispersal rates of biota and filter species by altering the local environmental conditions. Although phytoplankton is a key biotic group to indicate changes in aquatic environments, the effects of river damming on the longitudinal distribution of phytoplankton communities are not widely addressed. Here we investigated the changes on the taxonomic and functional composition of the phytoplankton community in a large tropical dammed river. We expect compositional changes to be higher at taxonomic than functional level especially in the dam-free stretches of the river because running waters select species able to cope with the water turbulence. Furthermore, flow regulation allows species with different traits to colonize the increasingly lentic stretches resulting in higher functional diversity towards dams. Phytoplankton samples were taken in 210 sites, spaced by 5 km, along the whole river channel. Data were split at a reservoir level considering the sites within 30 km before and after each dam to analyze the effects of damming on the community composition. Compositional changes were assessed by estimating the degree to which each community differed from all other communities within the regional pool (community distinctiveness) considering taxonomic and functional composition separately. Functional diversity was estimated as the degree to which species within the same community differed from each other with respect to their trait composition (functional dispersion). We used community-weighted means to test how the different traits were filtered by river damming. Furthermore, we assessed the effects of local environmental conditions on the phytoplankton taxonomic and functional composition using boosted regression trees (BRT). We observed no effects of river damming on species dispersal. Functional turnover was low, suggesting that compositional changes occurred mainly among functionally similar species. However, there was a noticeable reduction of phytoplankton diversity that persisted for more than 100 km after one of the dams. Flow regulation allowed flagellated and mucilaginous species to colonize the dammed areas. After the dams, such species were filtered due to the increase of water mixing downstream, as evidenced by a hump-shaped trend in the functional diversity of the sites within 30 km distance of the dams. BRT analyses highlighted the role of nutrient input in the dammed areas for the community compositional change. This study highlights the importance of considering both taxonomical and functional diversity to describe the effects of human intervention such as damming on aquatic ecosystems.
This work integrated a lab-made conductive graphite/polylactic acid (Grp/PLA, 40:60% w/w) filament into a 3D pen to print customized electrodes (cylindrical design). Thermogravimetric analysis ...validated the incorporation of graphite into the PLA matrix, while Raman spectroscopy and scanning electron microscopy images indicated a graphitic structure with the presence of defects and highly porous, respectively. The electrochemical features of the 3D-printed Gpt/PLA electrode were systematically compared to that achieved using commercial carbon black/polylactic acid (CB/PLA, from Protopasta®) filament. The 3D printed Gpt/PLA electrode “in the native form” provided lower charge transfer resistance (Rct = 880 Ω) and a more kinetically favored reaction (K0 = 1.48 × 10−3 cm s−1) compared to the 3D printed CB/PLA electrode (chemically/electrochemically treated). Moreover, a method by batch injection analysis with amperometric detection (BIA-AD) was developed to determine atorvastatin (ATR) in pharmaceutical and water samples. Using the 3D printed Gpt/PLA electrode, a wider linear range (1–200 μmol L−1), sensitivity (3-times higher), and lower detection limit (LOD = 0.13 μmol L−1) were achieved when compared to the CB/PLA electrode. Repeatability studies (n = 15, RSD <7.3%) attested to the precision of the electrochemical measurements, and recovery percentages between 83 and 108% confirmed the accuracy of the method. Remarkably, this is the first time that ATR has been determined by the BIA-AD system and a low-cost 3D-printed device. This approach is promising to be implemented in research laboratories for quality control of pharmaceuticals and can also be useful for on-site environmental analysis.
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•Thermoplastic carbon composite is proposed for the detection of atorvastatin.•The electrode was printed using a portable 3D pen.•Better analytical performance than a commercial conductive CB/PLA (protopasta®) filament was achieved.•The proposed electrode does not require surface treatment protocols.•First time that atorvastatin was determined by batch injection analysis.
Abstract Lycopene is a hydrocarbon-carotenoid commonly found in red fruits intake with major function correlated to antioxidative capacity in several pathological conditions, including cancer and ...cardiovascular diseases. Recently, lycopene has been associated with hematopoiesis, although the effects on B lymphocyte differentiation and antibody production are poorly understood. In this work, the principal aim was to investigate whether lycopene affects B lymphopoiesis and terminal differentiation into plasma cells. Distinct in vivo and in vitro strategies based on lycopene supplementation were used direct in Balb/c mice or in culture systems with cells derived of these mice. In the bone marrow, lycopene expanded B220+IgM- progenitor B cells and B220+IgM+ immature B lymphocytes. In the spleen, lycopene induced terminal CD138+ plasma cell generation. In the blood, we found prominent IgA and low IgM levels after lycopene administration. Interestingly, the pattern of peritoneal IgM+ and IgA+ B cells indicated a significant IgM-to-IgA class switching after lycopene injection. These data indicated that lycopene induces B cell differentiation into IgA-producing plasma cells. Thus, a new cellular function has been attributed to lycopene for B lymphocyte biology and possibly associated with humoral responses and mucosal immunity.
Abstract The trial was conducted to evaluate the supplementation of E. coli phytase on performance, weight and ash of bones, as well as to determine the bioavailability of P and cost/benefit of its ...use in diets. A total 1,890 Cobb male day old chicks were assigned to six treatments and seven replicates with 45 birds each, distributed in a completely randomized design. The treatments were: Positive Control; Negative Control (NC1) - reduction of 0.06% avP; Negative Control 2 (NC2) - reduction of 0.12% avP; NC2 + Phytase (120 OTU); NC2 + Phytase (180 OTU); NC2 + Phytase (240 OTU), being 1 OTU equivalent to approximately 2 FTU. With different phytase inclusions, it was possible to verify a gradual increase on body weight gain, feed intake, feed conversion ratio, viability and even the bone characteristics of broilers fed diets containing reduction of P. The closest levels to the highest studied (240 OTU) showed the best results. The replacement of dicalcium phosphate by phytase supplementation is economically viable when the cost per OTU does not exceed US$ 1.4 × 10-5, US$1.2 × 10-5 and US$ 1.0 × 10-5 for the concentrations of 120, 180 and 240 OTU, respectively.
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•A new carbon-composite material is proposed for the production of affordable sensors.•Carbon nitride provided electrocatalytic properties for the detection of amaranth.•Amaranth is ...determined for the first time using a 3D-printed electrochemical platform.•The proposed method can be applied to different food samples.•Results similar to those of UV–Vis spectrometry confirmed the method's accuracy.
The production of sustainable materials with properties aimed at the additive manufacturing of electrochemical sensors has gained prestige in the scientific scenario. Here, a novel lab-made composite material using graphite (G) and carbon nitride (C3N4) embedded into polylactic acid (PLA) biopolymer is proposed to produce 3D-printed electrodes. PLA offers printability and mechanical stability in this composition, while G and C3N4 provide electrical properties and electrocatalytic sites, respectively. Characterizations by Raman and infrared spectroscopies and Energy Dispersive X-rays indicated that the G/C3N4/PLA composite was successfully obtained, while electron microscopy images revealed non-homogeneous rough surfaces. Better electrochemical properties were achieved when the G/C3N4/PLA proportion (35:5:60) was used. As a proof of concept, amaranth (AMR), a synthetic dye, was selected as an analyte, and a fast method using square wave voltammetry was developed. Utilizing the 3D-printed G/C3N4/PLA electrode, a more comprehensive linear range (0.2 to 4.2 μmol/L), a 5-fold increase in sensitivity (9.83 μmol−1 L μA), and better limits of detection (LOD = 0.06 μmol/L) and quantification (LOQ = 0.18 μmol/L) were achieved compared to the G/PLA electrode. Samples of jelly, popsicles, isotonic drinks, and food flavoring samples were analyzed, and similar results to those obtained by UV–vis spectrometry confirmed the method's reliability. Therefore, the described sensor is a simple, cost-effective alternative for assessing AMR in routine food analysis.
This work exploits the applicability of a chemically reduced graphene oxide (CRGO) modification on the electrochemical response of a glassy carbon electrode (GCE) for the first-time sensitive ...determination of furosemide in natural waters. The batch injection analysis (BIA) is proposed as an analytical method, where CRGO-GCE is coupled to a BIA cell for amperometric measurements. Acetate buffer (0.1 μmol L
−1
, pH 5.2) was used as the background electrolyte. The modification provided an increase in sensitivity (0.024 μA/μmol L
−1
), low limit of detection (0.7 μmol L
−1
), RSD (< 4%), and broad linear range (1–600 μmol L
−1
). Recovery tests performed in two different concentration ranges resulted in values between 89 and 99%. Recovery tests were performed and compared with high-performance liquid chromatography (HPLC) with UV-Vis detection using Student’s
t
test at a 95% significance level, and no significant differences were found, confirming the accuracy of the method. The developed method is proven faster (169 h
−1
) compared with the HPLC analysis (5 h
−1
), also comparable with other flow procedures hereby described, offering a low-cost strategy suitable to quantify an emerging pharmaceutical pollutant.
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