Dry Season Research Articles

Effect of season on testicular morphometry and sperm production in adult guinea cocks

A study was conducted to investigate the effect of season on testicular morphometric parameters and sperm production in adult Guinea cocks. Five (5) Guinea cocks (GCs) were randomly selected from a group of thirty homogenous adult pearl Guinea cocks during the major rainy, minor rainy season, and dry seasons of the year. The selected GCs were humanely euthanized and used for determining testicular morphometric parameters, sperm reserve, and sperm production. The results of this study showed that the body weight of Guinea cocks (GCs) and testicular morphometric parameters were significantly (P<0.05) higher in the rainy season than in the dry season, while testicular weight and the gonado-somatic index (GSI) were similar. Sperm reserves and daily sperm production were significantly (P<0.05) higher in the rainy season than in the dry season. The study concluded that the season of the year affected the body weight of the Guinea cocks, testicular morphometric parameters, sperm reserve, and sperm production in adult Guinea cocks.

Assessing the ecological patterns of Aedes aegypti in areas with high arboviral risks in the large city of Abidjan, Côte d’Ivoire

Background The city of Abidjan, Côte d’Ivoire has increasingly faced multiple outbreaks of Aedes mosquito-borne arboviral diseases (e.g., dengue (DEN) and yellow fever (YF)) during the recent years, 2017–2023. Thus, we assessed and compared Aedes aegypti larval and adult population dynamics and Stegomyia indices in four urbanized areas with differential arboviral incidences in Abidjan, Côte d’Ivoire. Methods From August 2019 to July 2020, we sampled Aedes mosquito immatures (larvae and pupae), adults and breeding habitats in Anono and Gbagba with high arboviral incidences and Ayakro and Entente with low arboviral incidences in the Abidjan city, using standardized methods. Sampling was conducted in the peridomestic and domestic (indoors and outdoors) premises during short dry season (SDS), short rainy season (SRS), long dry season (LDS) and long rainy season (LRS). The abdomens and ovaries of Ae. aegypti females were examined to determine their blood-meal and parity statuses. Stegomyia indices (container index: CI, house index: HI and Breteau index: BI), blood-meal status and parity rates were compared by study sites and seasons and with the World Health Organization (WHO)-established epidemic thresholds. Results Overall, Aedes and arboviral risk indices were high and similar between the four study areas. In total, 86,796 mosquitoes were identified and dominated by Ae. aegypti species (97.14%, 84,317/86,796). The most productive larval breeding habitats were tires, discarded containers and water storage containers. CI, HI, and BI in Anono (22.4%, 33.5% and 89.5), Ayakro (23.1%, 43.8% and 91.0), Entente (15.9%, 24.8% and 48.5) and Gbagba (23.3%, 43.0% and 102.0) were high in the respective study sites. Stegomyia indices were higher than the WHO-established epidemic thresholds during any seasons for DEN, and LRS and SRS for YF. The numbers of Ae. aegypti-positive breeding sites were higher in the domestic premises (68.0%, 900/1,324) than in the peridomestic premises (32.0%, 424/1,324). In the domestic premises, Ae. aegypti-positive breeding sites (94.6%, 851/4,360) and adult individuals (93.4%, 856/916) were mostly found outdoors of houses. Aedes aegypti adult females were mostly unfed (51.3%, 203/396), followed by blood-fed (22.2%, 88/396), gravid (13.9%, 55/396) and half-gravid (12.6%, 50/396), and had parity rate of 49.7% (197/396) that was comparable between the study sites. Conclusions The city of Abidjan, Côte d’Ivoire is highly infested with Ae. aegypti which showed comparable ecological patterns across study sites and seasons. Thus, the local communities are exposed to high and permanent risks of transmission of DEN and YF viruses that were above the WHO-established epidemic thresholds throughout. The results provide a baseline for future vector studies needed to further characterize the observed patterns of local Ae. aegypti abundances and behaviors, and risks of transmission of these arboviruses. Community-based larval source management of identified productive containers might reduce Ae. aegypti numbers and risks of transmission of Aedes-borne arboviruses in Abidjan, and other sub-Saharan African cities.

Habitat Assessment of Bocachico (Prochilodus magdalenae) in Ciénaga de Betancí, Colombia, Using a Habitat Suitability Index Model

This study evaluates the habitat of the Bocachico fish (Prochilodus magdalenae) in the Ciénaga de Betancí, Colombia, using a habitat suitability index (HSI) model. Wetlands like the Ciénaga de Betancí are under significant pressure from anthropogenic activities, affecting biodiversity and ecosystem health. The Bocachico, a species of immense cultural and economic importance, faces habitat degradation and fragmentation. Using hydrodynamic and water quality data, a numerical model (EFDC+ Explorer 11.5), and field data collected from multiple sampling campaigns, we assessed habitat suitability based on five key parameters: water temperature, dissolved oxygen, ammonia nitrogen, velocity, and depth. The model results indicated that environmental conditions in the wetland remained relatively stable during the dry season, with an average HSI score of 0.67, where 9% of the wetland area displayed acceptable conditions, and the remaining 91% displayed medium conditions. The wet season, on the other hand, had an average HSI score of 0.64, with 7.2% of the area in the acceptable suitability range, and the remaining 92.8% in the medium category. Variations in HSI were primarily driven by ammonia nitrogen levels, water velocity, and depth. Despite limited fluctuations in the HSI, areas of low suitability were identified, particularly in regions impacted by human activities. These findings have practical implications for conservation strategies, providing valuable insights for the sustainable management and conservation of the Ciénaga de Betancí, informing strategies for improving habitat conditions for the Bocachico, and supporting wetland restoration efforts.

The E3 ligase TaE3V-B1 ubiquitinates proteins encoded by the vernalization gene TaVRN1 and regulates developmental processes in wheat

Abstract In wheat (Triticum aestivum), early maturity is desired to avoid the hot and dry summer season, especially in view of climate change. Here, we report that TaE3V1, a C3H2C3 RING-type E3 ligase that interacts with TaVRN1, is associated with early development. Aside from its RING domain, TaE3V1 does not harbor any domains that are conserved in other RING-type or other E3 ligase proteins. TaE3V-B1b, encoded by the functional TaE3V1 allele, interacts with and ubiquitinates TaVRN1. In contrast, TaE3V-B1a, encoded by a natural nonfunctional TaE3V1 allele, neither interacts with TaVRN1 nor has E3 ligase activity. TaE3V-B1b activity decreases with plant age under warmer temperatures, but not under the low temperatures required for vernalization. We employed a gene editing method to simultaneously inactivate the three homoeologous TaE3V1 genes to validate their functions. Overall, our results suggest that the naturally mutated and edited TaE3V1 alleles can accelerate wheat development and aid adaptation to warming climates.

A Statistical Evaluation of the Occurence of Meningitis in Takum, Taraba State, Nigeria

Meningitis remains a critical public health issue in Nigeria, particularly within the dry season when environmental factors such as low humidity and dust elevate transmission risks. Using historical incidence data from 2012 to 2021, this study utilizes the Autoregressive Integrated Moving Average (ARIMA) model estimate and predict the occurrence of meningitis occurrences. Findings frm the study revealed that the ARIMA(1,1,0) model emerged as the optimal fit, capturing the seasonal patterns and temporal trends in meningitis cases. This study recommends the integration of ARIMA-based forecasting into Nigeria’s public health strategies to strengthen early warning systems, optimize resource deployment, and enable more proactive responses during high-risk periods.

Relationships between flower-visiting insects and forest cover in cocoa-growing landscapes in Ghana

Abstract Context Increased cocoa cultivation (Theobroma cacao) has led to the conversion of over 6 million hectares of rainforest to cocoa farmlands in West Africa. Globally, pollinator decline has been driven by land use changes. Though land use change through cocoa expansion may affect insect pollinators and, by extension, pollination services, this has rarely been assessed. Objectives Our study examined the relationships between the proportion of natural forest in the landscape (reduced primarily due to cocoa expansion) and flower-visiting insect abundance, and bee abundance, richness, diversity and community composition. The effect of pan trap type (aerial or ground) was also tested. Methods Eighteen sites were selected along a gradient of an increasing proportion of natural forests in the surrounding landscape (from 9 to 100%). Ground and aerial pan traps were deployed in each site to sample flower-visiting insects. Two sampling sessions were conducted; during the rainy season in 2021 and during the dry season in 2022. Results The abundances of Coleoptera, Hymenoptera and Hemiptera increased with increasing proportion of natural forests in the landscape, while Diptera decreased. Natural forest and trap type did not significantly influence bee abundance, species richness, and Shannon diversity. However, bee community composition differed along the forest gradient, indicating that forests and cocoa farms harbour different bee communities. Ground pan traps captured more insects (61% of 19,927 flower-visiting insects) than aerial pan traps, which was driven by the Diptera as the abundances of the other orders were not significantly related to trap type. Conclusions Preserving natural forest in cocoa-growing landscapes is important to sustain the coexistence of diverse flower-visiting insect communities owing to their differential responses to the proportions of natural forests.

Field surveysin rural Tanzania reveal key opportunities for targeted larval source management and species sanitation to control malaria in areas dominated by Anopheles funestus.

Larval source management (LSM) is re-emerging as a critical malaria intervention to address challenges associated with core vector control tools, such as insecticide-treated nets (ITNs), and to accelerate progress towards elimination. Presently, LSM is not widely used in rural settings and is instead more commonly applied in urban and arid settings. A systematic entomological assessment was conducted in rural communities of southeastern Tanzania, where insecticide-treated nets (ITNs) are widely used, to explore opportunities for deploying LSM to improve malaria control. Aquatic habitat surveys were conducted in 2022 and 2023 to understand habitat usage by different mosquito vectors, covering five villages during the rainy season and seven villages during the dry season. Additionally, samples of adult mosquitoes were collected to assess the role of various Anopheles species in malaria transmission in the area, and to explore opportunities for species sanitation using targeted LSM. Adult mosquito surveys showed that in this area, the total entomological inoculation rates (EIR) for indoor collections were 20.1 and 6.5 infectious bites per person per year for outdoors. Anopheles funestus and Anopheles arabiensis were the only Anopheles vectors identified. Anopheles funestus was responsible for over 97.6% of the malaria transmission indoors and 95.4% outdoors. The concurrent larval surveys found that habitats with late instar An. arabiensis and An. funestus comprised only a small subset of 11.2%-16.5% of all water bodies in the rainy season, and 9.7%-15.2% in the dry season. In terms of size, these habitats covered 66.4%-68.2% of the total habitat areas in the wet season, reducing to 33.9%-40.6% in the dry season. From the rainy season to the dry season, the surface area of habitats occupied by An. arabiensis and An. funestus decreased by 92.0% to 97.5%, while the number of habitats occupied by An. arabiensis and An. funestus decreased by 38.0% to 57.3%. Anopheles funestus preferred large, permanent habitats with clear water and vegetation year-round, while An. arabiensis showed contrasting seasonal preferences, favouring sunlit still waters in the rainy season and larger, opaque habitats in the dry season. These findings suggest that An. funestus, which is the dominant malaria vector in the area, mediating over 95% of malaria transmission, preferentially occupies only a small subset of uniquely identifiable aquatic habitats in both wet and dry seasons. This presents an opportunity to expand LSM in rural settings by carefully targeting An. funestus habitats, which might be effective and logistically feasible as a complementary approach alongside existing interventions. Further research should assess the impact of targeted LSM for species sanitation compared to blanket LSM.

Determinant Factors of Microbial Drinking Water Quality at the Point of Use in Rural Ethiopia: A Case Study of the South Gondar Zone

Access to safe drinking water is a fundamental human need for health and well-being implemented globally by the United Nations under Sustainable Development Goal (SDG) 6. Storing drinking water is common in rural areas of Ethiopia due to off-premises water sources and intermittent piped water supply. However, this practice can lead to further contamination during collection, transport, and storage, posing a risk to public health. The objective of this study was to identify the determinant factors of drinking water quality at the point of use in the rural setting of northwestern Ethiopia, South Gondar zone. A questionnaire survey was conducted, and water samples from 720 households were collected during the wet and dry seasons. The determinant factors were identified using the multivariable logistic regression model. About 39.2% of the surveyed households had basic water supply services, 41.9% were using unimproved sources, and 8.3% were using surface water. Only 9.4% were using basic sanitation services, and 57.2% were practicing open defecation. Safe water storage was practiced by 84.3% of households, while only 2% engaged in household water treatment. About 14% of dry and 8% of wet season samples from the storage were free from fecal coliform bacteria. Furthermore, 52.9% of dry and 62.2% of wet season samples fell under the high microbial health risk category. The season of the year, the water source type, storage washing methods, and the socioeconomic status of the household were identified as key predictors of household drinking water fecal contamination using the multivariable logistic regression model. It was observed that the drinking water in households had a high load of fecal contamination, posing health risks to consumers. To tackle these problems, our study recommends that stakeholders should enhance access to improved water sources, implement source-level water treatment, increase access to improved sanitation facilities, advocate for safe household water management practices, and endorse household water treatment methods.

Population size and structure of Grant’s gazelle and lesser kudu in Geralle National Park, Southeastern Ethiopia

Background Grant’s gazelle and lesser kudu remain widespread within and outside protected areas. Current pressures on their populations, human encroachment and disturbance associated habitat modifications, and excessive grazing pose further threats to the species. The estimation of density and abundance of species has significant value for sustainable wildlife management in Geralle National Park (GNP) and also contributes towards a more accurate global population estimate. Result Using distance sampling methods, the lowest Akaike Information Criterion (AIC) (close to zero) and Chi-square tests (P value > 0.05) showed that the hazard rate key function with an un-equal interval group model was selected for estimation of density and abundance. The density of species was 1.7 ± 0.5, 2.07 ± 0.7, gazelle/km2 and 1.39 ± 0.3, 1.92 ± 0.42, lesser kudu/km2 during the dry and wet seasons, respectively. Population density, abundance, and structure showed habitat and seasonal differences in observation. More individuals of both species were recorded during the wet season as compared to the dry season. Grassland was favored by Grant’s gazelle, while lesser kudu preferred woodlands. Both species exhibited a female-biased sex ratio, indicating potential for future population growth prospects. Conclusion It can be concluded that GNP is home to viable populations of Grant’s gazelle and lesser kudu, and season has influenced population abundance and distribution due to resource availability variations among seasons. The female-biased sex ratio indicates the future population growth prospects for the two species.

Impacts of climate change and deforestation on fire risk in the Amazon basin

Fires in the Amazon rainforest are a result of anthropogenic activity in the region. As the Amazon rainforest becomes vulnerable to fire through deforestation and climate change, it is imperative to understand how the fire risk will change in future years—not only for the potential of the forest to become a source of carbon to the atmosphere if burned but also for the potential loss of unique biodiversity and its critical role in regional and global climate. Therefore, we used the Eta regional climate model driven by 3 global climate models to simulate 2 distinct scenarios: one with a high CO2 emission (RCP8.5-DEF15) path and another with a high CO2 emission path and the total deforestation of the Amazon rainforest (RCP8.5-DEFTOT). Combining the multi-model ensemble of temperature and precipitation, we calculated the Keetch-Byram Drought Index (KBDI) and analyzed the results for the dry and wet seasons. In both scenarios, precipitation is reduced and maximum temperature increased. The greatest changes occur during the dry season and with the RCP8.5-DEFTOT scenario. In RCP8.5-DEF15, the KBDI is greatly affected, showing positive anomalies in both seasons. With the addition of deforestation, the fire risk is further exacerbated, thus highlighting the role of the forest in suppressing optimal conditions for fire. Additionally, more than half of the basin area is predicted to experience a high risk of fire in extreme years. Our results emphasize the importance of reducing global emissions and deforestation of the Amazon, given that fire activity could threaten the future of the Amazon rainforest.

Projections of future bioclimatic indicators using bias-corrected CMIP6 models: a case study in a tropical monsoon region.

This study evaluates the potential impacts of climate change on Bangladesh by analyzing 19 bioclimatic indicators based on temperature and precipitation. Data from 18 bias-corrected CMIP6 global climate models (GCMs) were used, covering four Shared Socioeconomic Pathways (SSPs)-SSP126, SSP245, SSP370, and SSP585-across three future timeframes: near-term (2015-2044), mid-term (2045-2074), and long-term (2075-2100). Under the high-emission SSP585 scenario, average temperatures are projected to rise by up to 3.76°C, and annual precipitation could increase by 52.6%, reaching up to 3446.38mm by the end of the century. The maximum temperature (Bio5) could reach 32.91°C, while the minimum temperature (Bio6) might rise by 4.43°C, particularly during winter. Precipitation seasonality (Bio15) is projected to increase by as much as 7.9% in the northwest, indicating heightened variability between wet and dry seasons. The diurnal temperature range (Bio2) is expected to decrease by up to - 1.3°C, signifying reduced nighttime cooling, which could exacerbate heat stress. Significant reductions in temperature seasonality (Bio4) are forecast for the northeast, with notable declines in isothermality (Bio3) under SSP585, pointing to increased climatic extremes. These climatic shifts pose severe risks to agricultural productivity, water resource availability, and biodiversity, particularly in flood-prone regions. The findings highlight the need for urgent adaptation measures, including improved flood management systems, efficient water resource use, and climate-resilient agricultural practices. By providing robust region-specific projections, this study offers critical insights for policymakers and stakeholders to mitigate the adverse effects of climate change and safeguard environmental and economic sustainability in Bangladesh.

Characterization of the Elemental Composition of Aerosols Emitted in the Dry Season of the Pantanal Wetland, Brazil

The Brazilian Pantanal region experiences intense biomass burning during the dry season, releasing large quantities of gasses and particles into the atmosphere, which have serious implications on both the climate system and public health. Understanding the dynamics of these emissions is crucial for mitigating the impact on the ecosystem, its functioning, and potential anthropogenic disturbances. This study focused on analyzing emissions in the northern Pantanal during the 2022 drought. Concentrations of fine particulate matter (PM2.5), black carbon (BC), and 25 chemical elements were measured using gravimetry, reflectance analysis, and X-Ray fluorescence, respectively, from samples collected between August and October 2022. The average concentrations of PM2.5 and BC increased approximately 4-fold and 2.5-fold, respectively, compared to averages from a decade ago. Significant increases were also observed in elements such as sulfur (S), potassium (K), iron (Fe), and silicon (Si). The maximum concentrations were comparable to values typical of the southern Amazon, a region known for high deforestation rates and land use changes. Elemental analysis revealed substantial shifts in concentrations, primarily associated with biomass burning (BB) and soil suspension. Additionally, enrichment factor (Ef) analysis showed that lead (Pb) levels, correlated with human activities, were 200 times higher than those found under clean atmospheric conditions.

Remote sensing and GPS tracking reveal temporal shifts in habitat use in nonbreeding Black‐tailed Godwits

Abstract Knowledge of the habitat requirements for migratory species throughout their full annual cycle is necessary for comprehensive species protection plans. By describing seasonal shifts of space‐use patterns in a key nonbreeding area, the Senegal Delta (Mauritania, Senegal), this study addresses a significant knowledge gap in the annual cycle of the rapidly declining continental Black‐tailed Godwit Limosa limosa limosa. We fitted continuous‐time stochastic‐process movement models with GPS location data to describe the core areas used by 22 GPS‐tagged godwits over the 2022–2023 nonbreeding period. We mapped key habitat types, such as floodplain wetlands and rice fields, via supervised classification of satellite imagery. Godwits in the Senegal Delta show a distinct shift in habitat use over the nonbreeding period. The core areas of godwits in the early stages of the nonbreeding period (the wet season) were primarily in natural wetlands and fields with newly planted rice. As the rice crop matured and became too dense, godwits moved towards more recently sown rice fields. Later, as floodwaters receded and rice fields dried out, godwits abandoned rice fields and shifted towards natural wetlands with fewer invasive plants, particularly within the marshes and shallow floodplains of nature‐protected areas in the lower Delta. Synthesis and applications: Our findings illustrate the shifting importance of natural and agricultural wetlands for godwits at different stages of the nonbreeding season. Protected areas in the Senegal Delta, particularly the Djoudj National Bird Sanctuary (Senegal) and Diawling National Park (Mauritania), are crucial habitats during the dry season as godwits prepare for their northward migration, whilst rice fields take a key role during the wet season. Conservation efforts should prioritize eradicating invasive plants from the Djoudj and Diawling, as well as promote agroecological management in specific rice production complexes indicated in this study.

Spatiotemporal distribution in chemical composition of wet atmospheric deposition in Bandung Indonesia.

Bandung, Indonesia, represents the complex interactions between climate variability, basin topography, and deposition processes. This study conducted a long-term spatiotemporal analysis, including pH distribution and pollutant accumulation monitoring, to observe the chemical composition of wet deposition in Bandung as part of the Acid Deposition Monitoring Network in East Asia (EANET). The results revealed that and were the predominant ions, followed by , with their distribution varying across different sites due to local emissions and atmospheric processes. The interactions between these ions, particularly the formation of secondary inorganic aerosols such as ammonium sulfate and ammonium nitrate, were closely linked to the basin's localized sources and topographical features. Areas experiencing high traffic congestion were classified as acidic regions due to their low pH levels. In contrast, a rural site exhibited a basic pH due to the high concentration of ion . Variations in pH and conductivity, along with the impacts of climatic events such as El Niño and La Niña, emphasized the role of weather patterns in shaping wet deposition dynamics. Seasonal trends indicated elevated total ion concentrations during the dry season, driven by sea salt contributions, as supported by strong correlations between Na+ and and between Na+ and Mg2+. Additionally, geological materials and atmospheric reactions contributed to the strong correlations observed between soil-derived cations and acidic species. The increasing trend in and the contrasting decrease in concentrations in rural areas suggest evolving emission sources and environmental conditions.

Pertubations of Physicochemical Properties and Heavy Metal in the Soil of Coastal Areas of Akwa Ibom State, Nigeria

This study aimed at assessing the concentrations and perturbations of the physicochemical properties and heavy metals in the soil of the coastal regions of Akwa Ibom State, Nigeria. Sampling was carried out across three mangrove locations (Iko Town, Okoroutip and Uta Ewa) in Eastern Obolo, Ibeno and Ikot Abasi Local Government Areas respectively. Four vegetation plots were randomly selected, and within each plot, three belt transects were established. Physicochemical properties [Sand, Clay, Silt, organic carbon (OC), total nitrogen, sulphate and chlorine content] and heavy metals (Arsenic, Silver, Chromium, Copper, Nickel, Lead, Mercury, Cadmium, Titanium, Vanadium and Zinc) were analyzed using standardized methods. Results from this study revealed considerable variations in the physicochemical properties of soil in the study area. The aforementioned heavy metals were present in both wet and dry seasons in considerable concentrations in the soil samples within the study areas. However, were within and below WHO limits. The variations in the physicochemical properties and the presence of these heavy metals in the samples are indicative of an impacted environment unsuitable for the growth and survival of the endemic flora and fauna species of this unique ecosystem. In view of the current knowledge of the role of mangrove ecosystems in blue-economy of the nation and mitigation of ongoing climate change, we advocate a tripartite alliance between the government, multinational companies operating within the area and the various impacted communities that leads to a concerted efforts of constant monitoring and remediation in the reduction of current and future pollutant levels.

Advancing Water Security and Agricultural Productivity: A Case Study of Transboundary Cooperation Opportunities in the Kabul River Basin

The Kabul River Basin (KRB) is witnessing frequent flood and drought events that influence food production and distribution. The KRB is one of the world’s poorest regions regarding food security. Food security issues in the KRB include shifts in short-term climate cycles with significant river flow variations that result in inadequate water distribution. Due to the lack of hydro-infrastructure, low irrigation efficiency, and continuing wars, the Afghanistan portion of the KRB has experienced low agricultural land expansion opportunities for food production. This research assesses the relationship between flood mitigation, flow balances, and food production and, cumulatively, assesses the social and economic well-being of the population of the KRB. SWAT modeling and climate change (CCSM4) implications are utilized to assess how these relationships impact the social and economic well-being of the population in the KRB. The intricacies of transboundary exchange and cooperation indicate that the conservation of ~38% of the water volume would nearly double the low flows in the dry season and result in the retention of ~2B m3/y of water for agricultural developmental use. Results show that the peak flood flow routing in reservoirs on the Afghanistan side of the KRB would have a substantial positive impact on agricultural products and, therefore, food security. Water volume conservation has the potential to provide ~44% more arable land with water, allowing a ~51% increase in crop yield, provided that improved irrigation efficiency techniques are utilized.

Sentinel-1 data reveals unprecedented reduction of open water extent due to 2023-2024 drought in the central Amazon basin

Abstract In 2023, an intense drought impacted the Amazon basin triggered by climate change and a strong El Niño event, with the Negro River reaching its lowest water level in 120 years. However, the spatiotemporal open water extent (OWE) during this drought remains unclear. This study comprehensively evaluates OWE variability in the central Amazon using Sentinel-1 synthetic aperture radar (SAR) data since 2017. Monthly OWE masks were generated through an empirical threshold classification with accuracy >95%. Overall, the central Amazon experienced a reduction of ∼8% in OWE in the 2023 dry season months (November and December) when compared to monthly-average. However, reductions of up to 80% in OWE were observed in several specific lakes. Our analysis underscores the unprecedented severity of the 2023/2024 drought on rivers and floodplains. Utilizing SAR remote sensing technologies, this study emphasizes the urgent need for proactive conservation measures to safeguard the Amazon’s ecological integrity amid escalating environmental challenges. Monthly water masks from January/2017 to September/2024 are available here: https://doi.org/10.5281/zenodo.12751783.

Contrasting patterns of Asaia association with Plasmodium falciparum between field-collected Anopheles gambiae and Anopheles coluzzii from Cameroon.

The widespread prevalence of Asaia in mosquitoes makes it a potential candidate for paratrangenic control in Anopheles. To better understand whether this bacterium could be used for malaria control, we quantified Asaia in An. gambiae s.l populations in malaria endemic regions examining co-infection with Plasmodium falciparum. Adult Anopheles mosquitoes were collected across two different eco-geographical localities in Cameroon, during both the dry and wet seasons. DNA was extracted from whole individual mosquitoes, and real time-qPCR amplification of the 16S ribosomal RNA was used to quantify Asaia in both An. gambiae and An. coluzzii samples. We also detected and quantified P. falciparum infection in the same mosquitoes. The density of Asaia was successfully quantified in a total of 864 field mosquitoes, comprising of 439 An. gambiae from Bankeng and 424 An. coluzii collected from Gounougou. Interestingly, a higher prevalence of Asaia in An. gambiae (88.3%) compared to An. coluzzii (80.9%) was observed. Moreover, the density of Asaia in both species was significantly affected by seasonal changes in the two localities. Furthermore, a significant difference between the infection densities of Asaia and the Plasmodium infection status in the two species was recorded. However, no correlation was observed between the number of Asaia and P. falciparum infections. This study provides evidence that naturally occurring Asaia infection is not correlated to P. falciparum development within An. gambiae and An. coluzzii. Nevertheless, further studies incorporating experimental infections are required to better investigate the correlation between Anopheles mosquitoes, Asaia, and Plasmodium.IMPORTANCEThe symbiont Asaia has emerged as a promising candidate for paratransgenic control of malaria, but further analysis of its biology and genetics across Africa is necessary. In this study, we investigated and quantified the influence of Asaia in naturally infected An. gambiae s.l. populations with the malaria parasite Plasmodium falciparum. Genomic DNA was extracted from whole individual mosquitoes collected from two localities, and Asaia was quantified using real-time qPCR by amplification of the 16S ribosomal RNA gene. We also detected and quantified Plasmodium falciparum infection in the same mosquitoes and established the correlation between Asaia and Plasmodium coinfection. This study provides evidence that naturally occurring Asaia infection is not correlated with P. falciparum development within An. gambiae and An. coluzzii mosquitoes.

Evaluating the impact of climate change on yield and water use efficiency of different dry-season rice varieties cultivated under conventional and alternate wetting and drying conditions.

This study is the first attempt to assess rice cultivation under alternate wetting and drying (AWD) and continuous flooding (CF) using the latest scenarios from the Intergovernmental Panel on Climate Change(IPCC), utilizing AquaCrop Model. Field experiments were conducted during the dry season 2023 to get the model calibration and validation input. We used two shared socioeconomic pathways scenarios (SSP3-7.0 and SSP5-8.5) developed within Coupled Model Intercomparison Project Phase 6 (CMIP6) and projected the rice growth during 2040-2070. The simulation results demonstrated the effectiveness of AquaCrop in capturing crop development across treatments and varieties. This model's accuracy in simulating canopy cover (nRMSE = 14-32.5%), time series biomass (nRMSE = 22-42.5%), grain yield (Pd = 4.36-24.38%), and total biomass (nRMSE = 0.39-18.98%) was generally acceptable. The analysis of future climate shows an increasing trend in the monthly average temperature by 0.8°C (Tmin) and 1.3°C (Tmax) in both scenarios. While ETo values were not anticipated, rainfall was expected to increase with average values of 5.62mm to 11.25mm. In addition, the study found that varieties with growing periods longer than 93days after transplanting (DAT), such as CAR15 and Sen Kra Ob, were most impacted by heat stress conditions, leading to reduced yield, harvest index (HI), and water use efficiency (WUE). In our case, CAR15 and Sen Kra Ob grain yields were reduced by 53% and 8%, respectively. AWD maintains superior WUE compared with CF regardless of the type of varieties, suggesting this technique is a drought-adaptive strategy.

Organic matter processing by heterotrophic bacterioplankton in a large tropical river: Relating elemental composition and potential carbon mineralization.

River hydrology shapes the sources, concentration, and stoichiometry of organic matter within drainage basins. However, our understanding of how the microbes process dissolved organic matter (DOM) and recycle nutrients in tropical rivers needs to be improved. This study explores the relationships between elemental DOM composition (carbon/nitrogen/phosphorus: C/N/P), C and N uptake, and C mineralization by autochthonous bacterioplankton in the Usumacinta River, one of the most important fluvial systems in Mexico. Our study investigated changes in the composition and concentration of DOM and evaluated carbon dioxide (CO2)production rates (C-CO2) through laboratory experiments. We compared three sites representing the middle and lower river basins, including their transitional zones, during the rainy and dry seasons. After incubation (120 h at 25°C), the DOM decreased between 25% and 89% of C content. Notably, the initial high proportion of C in DOM in samples from the middle-forested zone and the transition led to elevated C-CO2 rates (>10 mg l-1 day-1), in contrast to the lower initial C proportion and subsequent C-CO2 rates (<7 mg l-1 day-1) in the lower river basin. We also found that dissolved organic carbon uptake and NO3- and NH4+ production were higher during the dry season than in the rainy season. The low water flow in the river during the dry season accentuated the differences in elemental composition and microbial processing of DOM among the sites, while the high water flow of the rainy season homogenized these factors. Our findings indicate that microbial metabolism operates with reduced efficiency in C-rich environments like forests, particularly when faced with high C/N and C/P ratios in DOM. This study highlights the influence of the tropical hydrological regime (rainy and dry seasons) and the longitudinal changes in the river basin (middle and lower) topography and land cover on microbial metabolism by constraining DOM characteristics, emphasizing the crucial role of elemental ratios in river DOM processing.