Main Basin Research Articles

Phytoplankton Composition in Relation to Its Nutritional Value in Burullus Lagoon, Egypt

Burullus Lagoon is a brackish water lake in the Nile Delta of Egypt. This study assumed that changes in environmental conditions affect phytoplankton species composition and their biochemical structure. The biochemical content of phytoplankton is considered as an initiatory study at Lake Brullus. Winter versus summer cruises from twelve sites representing the eastern, middle and western main lake basins were performed during 2018. Phytoplankton revealed a seasonally variation which attained the lowest value during winter season (72300 Unit/L) and the highest levels during summer season (88700 Unit/L). This is coincided with high total protein content (2692.5 mg/l) in summer. Chlorophyceae was the first major class by (37.9 %) followed by Bacillariophyceae (29.31%), then Cyanophyceae (20.7%), while, Euglenophyceae and Dinophyceae are rare classes constitute (8.63% and 3.4% respectively). Middle of the lake recorded the maximum total biochemical contents in winter (870.5, 57.6 and 6.1 mg/l of proteins, carbohydrates and lipids, respectively), this results corresponding to the elevation of total phytoplankton density at this central basin (29200 Unit/L), especially the Chlorophyceae (13700 Unit/L). The western basin had an optimum total biochemical structure in summer (1909.1, 55.4 and 6.5 mg/l) of proteins, carbohydrates and lipids, respectively, where phytoplankton was increased to 56000 Unit/L. The middle and western basins lied in mesotrophic to eutrophic state according to the Q index. Excessive nutrients loads by drainage water into the lagoon lead to significant pronounced effect in the phytoplankton biodiversity raise the urgent need for lagoon management strategies.

Eco-efficiency measurement as an approach to improve the sustainable development of municipalities: A case study in the Midwest of Brazil

Global challenges related to energy consumption, water scarcity, deforestation, and environmental pollution have a direct impact on municipalities in Brazil and other countries around the world. Thus, the present study aims to evaluate eco-efficiency and its determinants in 41 Brazilian municipalities between 2014 and 2016 in the area covered by the Araguaia River Valley, in the Midwest of Brazil, Goiás state region. The Araguaia River Valley is considered of economic and especially environmental importance. It is located in one of the main Brazilian river basins, adjacent to states comprising the Legal Amazon, one of the world's most important biomes. To measure the eco-efficiency rate, we applied Data Envelopment Analysis (DEA) via the model of output-oriented variable returns to scale (VRS). Variables used as input include Energy Consumption, Water Consumption, Number of Inhabitants, Fleet of Vehicles, Territorial Area, Deforested Area, and output is the ratio between GDP per capita and Deforested Area. In the second stage, we used Tobit regression with eco-efficiency rate as the dependent variable. For the analyzed period, results show low mean eco-efficiency in the VRS model, with values of 0.45 (2014) and 0.48 (2016). Results indicate that the municipalities of Castelândia in 2014, and Santo Antônio da Barra in 2016, achieved a sustainable balance between environmental and economic variables, contributing to conservation. That suggests that these municipal areas be a benchmark for the others and to local and national public managers, as well as the effective DEA technology applicability in calculating eco-efficiency. In contrast to these two cases, the Mineiros municipality (Araguaia River headwater area) obtained a very low eco-efficiency score. This is extremely concerning since this is an important and sensitive area in this region. In the second stage of the research, the Tobit model indicates that Deforested Area in 2014 and 2016 was significant and negatively correlated with the dependent variable, while Water Consumption (2016) was positively correlated with eco-efficiency. However, the robustness test shows the significant and negative correlation between Water Consumption and eco-efficiency in both years, additionally, the test confirms the results for the Deforested Area variable. These results are important to support policymakers and public managers in the development of more sustainable and eco-efficient municipalities worldwide.

Formation and Persistence of Extensional Internally Drained Basins: The Case of the Fucino Basin (Central Apennines, Italy)

AbstractThe interaction between sedimentation/erosion and faulting represents one of the most intriguing topics in landscape and tectonics evolution. Only few studies have been able to document the feedback between faulting and sedimentary loading from field observations. Here, we focus on how sediment loading/unloading influences the dynamics of fault systems in the Fucino basin, in the Central Apennines (Italy). The Fucino basin represents a remarkable case study with respect to the other main extensional basins in the Apennines because of its large dimension, square shape, significant sediment thickness, and its endorheic nature throughout its evolution.We present a detailed structural and geomorphologic analysis of the Fucino basin and its surroundings, investigating the kinematic and geometry of each main fault strand. The slickenlines analysis reveals multiple families of slip‐vectors and timing of activity, suggesting a change in extension slip‐direction from N240° to N200° during middle Pleistocene. Using a local isostatic model, we estimate that up to the 30% of the vertical geological displacement of the faults, which overall ranges from 0.5 to 2.5 km, is related to the sediment loading/unloading. We demonstrate a positive feedback between sedimentation and faulting which may also lead to a reorganization in fault kinematics related to a significant increase in vertical stress. We propose a conceptual model for the permanent endorheic configuration of the Fucino basin, which includes the effect of sediment loading.

Aetiology of garlic rot, an emerging disease in France

AbstractThe incidence of garlic rot has constantly increased in France since the early 2000s. To set up an efficient method of garlic protection against this disease, we have clarified its aetiology. This was achieved by surveying garlic from the two main French basins of garlic production over 3 years. Fungi were isolated from 5,493 garlic cloves belonging to pink, purple, and white garlic types. Sequencing of the translation elongation factor 1α gene of 1,171 strains revealed that 94% of the strains belonged to the species Fusarium proliferatum and 6% belonged to F. oxysporum. The pathogenicity of both species on garlic was confirmed by artificial inoculations and reisolations. There was significantly more F. oxysporum in garlic cloves with symptoms coming from the southeast basin (9.44%) than from the southwest basin (2.76%). This study confirms that garlic rot is present in pink, purple, and white types. However, pink type garlic harbours F. oxysporum significantly less frequently (1.59%) than white (9.39%) and purple (7.34%) types. Sequencing of rpb1, rpb2, ITS, and IGS regions of a subsample of strains revealed that there is little genetic diversity in the French population of F. proliferatum.

Spatio-Temporal Assessment of Global Gridded Evapotranspiration Datasets across Iran

Estimating evapotranspiration (ET), the main water output flux within basins, is an important step in assessing hydrological changes and water availability. However, direct measurements of ET are challenging, especially for large regions. Global products now provide gridded estimates of ET at different temporal resolution, each with its own method of estimating ET based on various data sources. This study investigates the differences between ERA5, GLEAM, and GLDAS datasets of estimated ET at gridded points across Iran, and their accuracy in comparison with reference ET. The spatial and temporal discrepancies between datasets are identified, as well as their co-variation with forcing variables. The ET reference values used to check the accuracy of the datasets were based on the water balance (ETwb) from Iran’s main basins, and co-variation of estimated errors for each product with forcing drivers of ET. The results indicate that ETERA5 provides higher base average values and lower maximum annual average values than ETGLEAM. Temporal changes at the annual scale are similar for GLEAM, ERA5, and GLDAS datasets, but differences at seasonal and monthly time scales are identified. Some discrepancies are also recorded in ET spatial distribution, but generally, all datasets provide similarities, e.g., for humid regions basins. ETERA5 has a higher correlation with available energy than available water, while ETGLEAM has higher correlation with available water, and ETGLDAS does not correlate with none of these drivers. Based on the comparison of ETERA5 and ETGLEAM with ETwb, both have similar errors in spatial distribution, while ETGLDAS provided over and under estimations in northern and southern basins, respectively, compared to them (ETERA5 and ETGLEAM). All three datasets provide better ET estimates (values closer to ETWB) in hyper-arid and arid regions from central to eastern Iran than in the humid areas. Thus, the GLEAM, ERA5, and GLDAS datasets are more suitable for estimating ET for arid rather than humid basins in Iran.

Integrated Hydrologic Study of the Arid and Semi-arid Regions using RST and GIS in the Riyadh Metropolitan Area, Saudi Arabia

Abstract Water is extremely critical for human survival. It is therefore important to efficiently manage integrated water resources, which includes basins, watersheds, and wadies. In this study, the freely available data was used, which included a digital elevation model, soil and geological maps, satellite imageries, and daily precipitation records. Furthermore, remote sensing techniques and geographic information system were also integrated in this study. The linear and areal aspects, along with the longitudinal profile were also included, and the hydrologic soil groups (HSGs), land use/land cover (LULC), and curve number (CN) were identified for the main basin of the Riyadh capital. The morphometric analysis indicated that the total area of the main basin was 8500 km2, with 40 watersheds and the highest stream order as eighth. The drainage density of the main basin was 1.57 km/km2. Impermeable surface constituted most of the basin area, as group D was the most prevalently found HSG, constituting 71% of the total basin area. Additionally, the main basin had a highly steep slope, with varying elevations. Furthermore, four types of LULC were identified in the basin namely urban-based, barren land, cultivated land, and ways. The CN for every cell of the main basin ranged from 64 to 98, and the basin weighted CN was found to be 92. The potential direct runoff ranged from 10 to 59 mm. More than 70% of the total area was found to be vulnerable to high and very high runoffs (> 35 mm). These values confirmed the occurrence of flood events, particularly in urban areas and cultivated lands.

Spatial and temporal distributions of Dreissena spp. veligers in Lake Huron: Does calcium limit settling success?

The larval stage of invasive Dreissena spp. mussels (i.e., veligers) are understudied despite their seasonal numerical dominance among plankton. We report the spring and summer veliger densities and size structure across the main basin, North Channel, and Georgian Bay of Lake Huron, and seek to explain spatiotemporal variation. Monthly sampling was conducted at 9 transects and up to 3 sites per transect from spring through summer 2017. Veliger densities peaked in June and July, and we found comparable densities and biomasses of veligers between basins, despite differences in density of juvenile and adult mussels across these regions. Using a generalized additive model to explain variations in veliger density, we found that temperature, chlorophyll a, and nitrates/nitrites were most important. We generated an index of veliger attrition based on size distributions that revealed a higher rate of attrition in the North Channel than the rest of the lake. A logistic model indicated a threshold calcium concentration of around 22 mg/L was necessary for veligers to survive to larger sizes and recruit to their juvenile and benthic adult life stages. Improved understanding of factors that regulate the production and survival of Dreissena veligers could improve the ability of managers to assess future invasion threats as well as explore potential control options.

Evaluation of the effect of carbamazepine on the concentration of vitellogenin in Pseudoplatystoma magdaleniatum

Abstract Carbamazepine is a pharmaceutical used in patients with seizures and bipolar disorder, which has been found in wastewater and many water resources. This is due to the inadequate disposal of pharmaceutical waste and the lack of treatment of municipal wastewater, as is the case in Colombia. The two main hydrographic basins of Colombia are the Cauca and Magdalena rivers, which are inhabited by the endemic species Striped Catfish (Pseudoplatystoma magdaleniatum). This has become an endangered species for various reasons, including the high contamination level of these rivers. In 2019, mature adult P. magdaleniatum of both sexes were caught in the Cauca river in Colombia. This was in order to assess the concentration of vitellogenin, as a biomarker of endocrine disruption, resulting from exposure to different levels of concentration of the emerging contaminant carbamazepine for 4 months. These tests were carried out in a fish farm. A significant decrease in the vitellogenin concentration was verified in females at concentrations of 25 µg l-1 and 50 µg l-1, and in males at 50 µg l-1 of carbamazepine, with a significance level of p˂0.05. Carbamazepine could cause a negative feedback in gonadotropin secretion, acting as an estrogen mimicker that causes a decrease in the level of vitellogenin.

Population Dynamics of Intermediate-Host Snails in the White Nile River, Sudan: A Year-Round Observational Descriptive Study.

We aimed to explore the population dynamics of snail in 3 sites of the White Nile in Sudan. More specifically, we aimed to investigate the annual patterns of snail populations that act as intermediate hosts of schistosomes and monthly snail infection rates and ecological characteristics presumably related to snail populations. We collected snails for 1 year monthly at 3 different shore sites in the vicinity of El Shajara along the White Nile river in Khartoum State, Sudan. In addition, we measured air and water temperatures, water turbidities, vegetation coverages, and water depths and current speeds. Most of the collected snails were Biomphalaria pfeifferi and Bulinus truncatus. The population densities of snails and their infection rates varied across survey sites. The collected snails liberated S. mansoni and S. haematobium cercariae as well as Amphistome and Echinostome cercariae. Infected snails were found during March–June. The ecological characteristics found to be associated with the absence of snails population were: high turbidity, deep water, low vegetation coverage (near absence of vegetation), high water temperature, and high current speed. To our knowledge, this is the first longitudinal study of the snail population and ecological characteristics in the main basin of the White Nile river.

Analysing Trends and Spatio-Temporal Variability of Precipitation in the Main Central Rift Valley Lakes Basin, Ethiopia

This study aims to investigate trends and spatiotemporal variability of precipitation during the period of 1980-2015 in the Main Central Ethiopian Rift Valley Lakes Basin. Mann-Kendall (MK) and Sen’s Slope (SS) estimation were used to detect the trends and magnitudes respectively. The Inverse Distance Weighting method was employed for spatial interpolations. The results revealed that the rainfalls had experienced less concentrated and highly variable in the central rift floor. The trend analysis showed that out of 21 stations, 4 stations (Koshe, Bulbula, Kofole and Shashamane) in annual; six stations (Koshe, Bulbula, Tora, Wulberg, Wondogenet, and Shashamane) in spring; and only one station (Shashamane) in summer showed significantly decreasing trends with -4.5 to -15.59 mm/year range. All stations in spring rainfall revealed no positive trends. Conversely, in both annual and summer rainfall statistically significant increasing trends exhibited for Ejersalelle and Adamitulu with 6.4 to 7.94mm/year range. In monthly time scales, the significant decreasing and increasing trends were also investigated for a few stations. Increasing trends could lead to an increase in potential for water resources whereas variability and decreasing trends could boost over-exploitation of water resources. This study would be provided useful information for management of water resources in the study area.

PFAS accumulation in indigenous and translocated aquatic organisms from Belgium, with translation to human and ecological health risk

BackgroundDespite specific restrictions on their production and use, per- and polyfluoralkyl substances (PFAS) are still omnipresent in the environment, including aquatic ecosystems. Most biomonitoring studies have investigated the PFAS concentrations in indigenous organisms, whereas active biomonitoring has only been used sporadically. In the present study, accumulated PFAS concentrations were measured in indigenous fish, European perch (Perca fluviatilis) and European eel (Anguilla anguilla), and in translocated freshwater mussels (Dreissena bugensis and Corbicula fluminea) at 44 sampling locations within the main water basins of Flanders, the northern part of Belgium. Finally, both human health risk and ecological risk were assessed based on accumulated concentrations in fish muscle.ResultsAmong locations, ΣPFAS concentrations ranged from 8.56–157 ng/g ww (median: 22.4 ng/g ww) in mussels, 5.22–67.8 ng/g ww (median: 20.8 ng/g ww) in perch, and 5.73–68.8 ng/g ww (median: 22.1 ng/g ww) in eel. Concentrations of PFOA and PFTeDA were higher in mussels compared to fish, whereas for PFDA and PFUnDA the opposite was true. A comparison of concentrations on a wet weight basis between both fish species showed significantly higher PFDoDA, PFTrDA, PFTeDA and PFOA concentrations in eel compared to perch and significantly higher concentrations of PFDA and PFOS in perch. In mussels, PFAS profiles were dominated by PFOA and showed a higher relative contribution of short-chained PFAS, while PFAS profiles in fish were dominated by PFOS. Furthermore, all mussel species clearly occupied a lower trophic level than both fish species, based on a stable isotope analysis.ConclusionsBiomagnification of PFDA, PFUnDA and PFOS and biodilution of PFOA and PFTeDA were observed. Translocated mussels have been proven suitable to determine which PFAS are present in indigenous fish, since similar PFAS profiles were measured in all biota. Finally, mean PFAS concentrations in fish did pose a human health risk for eel, although tolerable daily intake values for perch were close to the reported daily consumption rates in Belgium and exceeded them in highly contaminated locations. Based on the ecological risk of PFOS, the standard was exceeded at about half of the sampling locations (44% for perch and 58% for eel).

Cyprinodontiform fishes of El Salvador

Introduction: The Cyprinodontiformes are a group of secondary freshwater fishes widely distributed in El Salvador. Currently, many species of this group are usually incorrectly identified for lack of adequate tools. Additionally, their taxonomy and distribution have changed in recent years. Objective: To provide updated information about the taxonomy and distribution of El Salvador Cyprinodontiformes through identification keys, distribution notes, and general descriptions for all species. Methods: We carried out an extensive review of the literature, electronic databases, and museum specimens to generate a list of valid species present in El Salvador. Results: Eleven species in three families are confirmed: Profundulidae (two species), Anablepidae (one species), and Poeciliidae (eight species). We also include distribution data, both vertical and by main basins, and an illustrated guide. Conclusions: There are 11 species of Cyprinodontiformes in El Salvador and they can be found and identified with this article.

Morphometry of AFs in upstream and downstream of floods in Gribayegan, Iran

This study aims to determine the effect of a flood-spreading system on the morphometric characteristics of alluvial fans (AFs) in Gribayegan Fasa, Iran, and its relationship with erosion, age, texture, and type of formations. After determining the AFs using the semiautomatic method and determining their recharged watersheds, 25 morphometric characteristics were investigated. The most important morphometric characteristics were identified using principal component analysis (PCA). The group method of data handling (GMDH) neural network is used to predict erosion, soil texture, age, and formation material based on the morphometric characteristics of the fan. The results demonstrate that the semiautomatic method can effectively extract AF from the landscape. The results of AF morphometry before and after flood spreading show that the fan area, drainage basin circularity (Cirb), fan perimeter, relief ratio of the fan, fan length, minimum fan height, and maximum fan height were higher before flood spreading, and basin shape, St (soil texture), upper fan slope, fan volume, and sweep angle had higher values after the flood. In addition, the results of PCA show that fan area, fan perimeter, fan length, fan radius, fan volume, basin area, basin perimeter, main channel length, basin length, and drainage density are important factors. The results of the GMDH algorithm reveal that this method can accurately predict the formation, age, soil texture, and erosion rate using morphometric characteristics. Therefore, the R2 is 0.92 for the formation age and R2 is 0.86 for the erosion rates, formation types, and soil texture, respectively. Therefore, the most important morphometric parameters can be determined using PCA, and the conditions and processes in the basin, such as formation material, age, soil texture, and erosion rate, can be predicted with high accuracy using the GMDH algorithm.

Evaluation of lake wetland ecotourism resources based on remote sensing ecological index

The quality of ecological environment is not only an important basis for judging the sustainable development of economy but also an important factor to complete the construction of ecological civilization. Therefore, this paper puts forward the application of remote sensing ecological index to evaluate the lake wetland ecotourism resources. In this study, the Manas Lake wetland area in Xinjiang was taken as the research object, and based on the remote sensing ecological index evaluation method, the ecological resources of Manas Lake wetland were evaluated. The results showed that RSEI (Remote Sensing Based Ecological Index) showed a steady upward trend from 2000 to 2016, which reflected that the ecological environment of the study area had been improved in the past 20 years; the area with poor ecological environment condition was 4.02 km2, the area improved was 8.18 km2, and the area with little change or unchanged was 3543 km2; the area around the downstream corridor was the main area with poor ecological quality, around the lake, and far away surrounding the area for improvement. Climate change and human activities have a common effect on the ecological environment of Manas Lake wetland. Increasing human activities are the main reason for wetland degradation. Over the years, extensive agricultural development has caused serious imbalance among population, economy, and ecological environment in Manas River Basin. From the perspective of optimizing the allocation of water resources, it is proposed that the ecological value and sustainable development of tail lake wetland should be paid attention to while the large-scale development of water and soil resources in the main source river basins.

Pore resistivity variation by Resistivity imaging technique in sedimentary part of main Gadilam river basin, Cuddalore District, Tamil Nadu, India

Electrical resistivity is the only property of physics which give information of subsurface moisture content in the formation, Hence geophysical electrical resistivity survey was carried out to investigate the nature of shallow subsurface formations and geological contact in the main Gadilam river basin of Cuddalore District in Tamil Nadu. Twenty-seven vertical electrical soundings (VES) were conducted by Schlumberger configuration in the basin. Data is interpreted by curve matching techniques using IPI2 WIN software, layer parameters like apparent resistivity (?a) and thickness (h) interpretation were exported to Geographic Information System (GIS). Interpretation distinguishes three major geoelectric layers like topsoil, sandy clay layer, clayey sand layer along the contact zone in the basin. Interpreted VES sounding curves are mostly four-layer cases of QH, H, HA and KH type. Investigation demarcates lithology of subsurface and hydrogeological set up by employing maximum possible electrode sounding to infer saline water and freshwater occurrence based on resistivity signals. Zone of groundwater potential map was prepared with the combination of resistivity (?= ?1+ ?2+ ?3+ ?4) and corresponding thickness (T= T1+T2+T3+T4). High resistivity value of >200 ? m and low resistivity value of <10 ? m show the occurrence of alkaline and saline water within the formation aquifers as a result of possible rock water interaction and saline water dissolution. Four-layer resistivity cases from the matched curve (namely KH, AH, QA, and KA type) show the resistivity distribution/variation. It separates the freshwater depth wish from 1 to 140 ? m in fluvial sediments. Flood basin, sandstone and clay layer with low resistivity value of 3.16 - 7.5 ? m indicates contact with saline and freshwater aquifer. The Iso – resistivity map delineates saline water and freshwater zones with in the fourth layer cases in the same locations to indicate the irrational way of abstracting groundwater, resulting in saltwater ingress.

New insights into the contribution of gravity data for mapping the lithospheric architecture

Amongst all the potential field methods, gravity data constitutes the frequently measured geophysical information for deep seated lithospheric structures. The present work aims to outline the structural pattern, the main basins of Sinai and the depths to both Conrad and Moho discontinuities (CMD) by utilizing the gravity data. Several basins were depicted based on high-pass filtered gravity map and much of them are in a close agreement with the former studies. Additionally, the dominant fault trends are NE, NW, EW and ENE. An empirical equation was applied to low-pass-filtered gravity data to estimate the depth of the CMD. However, the thickness of the sedimentary basins increases northwards, reaching approximately 8 km, the minimum depths of Conrad and Moho discontinuities were attained in the northern compartments to be about 18 and 31 km respectively. Meanwhile, far a way to the south, the maximum detectable depth of Conrad and Moho discontinuities are 21 and 37 km. Eventually, 2D gravity modeling was constructed and constrained by 15 drilled wells and the calculated depth of CMD to figure out the comprehensive lithospheric geometry beneath Sinai Peninsula.

Potential Effects of Bigheaded Carps on Four Laurentian Great Lakes Food Webs

AbstractBigheaded carps (BHCs; Silver Carp Hypophthalmichthys molitrix and Bighead Carp H. nobilis) are economically and culturally important in Asia and Europe but are considered highly invasive throughout the Mississippi River watershed and pose a threat to the food web and fisheries of the Laurentian Great Lakes. We used the Ecopath with Ecosim model framework to evaluate potential risk of BHC population growth and food web effects in four Great Lakes habitats, including mesotrophic waters of Saginaw Bay (Lake Huron) and Lake Erie and the oligotrophic main basins of Lakes Michigan and Huron. We simulated BHC population growth and food web effects under different scenarios of BHC production rates, prey vulnerability to BHCs, and availability of age‐0 BHCs to predation by salmonines. In the main basins of Lakes Michigan and Huron, the projected BHC population growth was low or negative, with a projected final BHC biomass of 0.5–1.1 times the initial introductory biomass (2% of total fish biomass for each BHC species), and BHCs had negligible effects on most food web groups across all scenarios. In contrast, in Saginaw Bay and Lake Erie, the projected BHC biomass was 2.5–12.5 times higher than the initial biomass across all scenarios, and the largest increases occurred under scenarios of high prey vulnerability to BHCs and high BHC production rates. High projected BHC biomass in Saginaw Bay and Lake Erie had negative effects on zooplankton and planktivorous fish groups and mixed effects on piscivores but had relatively negligible effects on most other food web groups across all scenarios. Our results are consistent with reported BHC effects on food webs in the Mississippi River and its tributaries and inform efforts to prevent BHC invasion of the Great Lakes.

Bedding-parallel calcite veins as a proxy for shale reservoir quality

The Ordovician-Silurian Sichuan, Eocene Bohai Bay and Eocene Nanxiang Basins have been the main productive basins of shale oil and gas in China. Bedding-parallel calcite veins-bearing intervals are found to coincide with the shale gas- and/or shale oil-producing layers. Bedding-parallel calcite veins-bearing shale intervals are demonstrated to be always overpressured, organic-rich, mature and brittle, and they generally have higher porosity, higher permeability and higher gas/oil content than adjacent layers. A systematic study on the genetic mechanism of these veins confirms that the above phenomenon is prevalent in the three above mentioned basins and other sedimentary basins. Bedding-parallel calcite veins are viewed as a proxy for shale reservoir quality. This proxy helps geologists to preliminarily determine the potential shale reservoir layers out of the thick shale successions before systematic organic-inorganic tests, because it can be easily identified in cores, outcrops and well logs, thereby contributing to economic and time-efficient exploration. Therefore, occurrence of bedding-parallel calcite veins in shale reservoir exploration needs further attention, especially in petroliferous basins where shale reservoir exploration is still in its infancy.

Changing sources and processes sustaining surface CO<sub>2</sub> and CH<sub>4</sub> fluxes along a tropical river to reservoir system

Abstract. Freshwaters are important emitters of carbon dioxide (CO2) and methane (CH4), two potent greenhouse gases (GHGs). While aquatic surface GHG fluxes have been extensively measured, there is much less information about their underlying sources. In lakes and reservoirs, surface GHG can originate from horizontal riverine flow, the hypolimnion, littoral sediments, and water column metabolism. These sources are generally studied separately, leading to a fragmented assessment of their relative role in sustaining CO2 and CH4 surface fluxes. In this study, we quantified sources and sinks of CO2 and CH4 in the epilimnion along a hydrological continuum in a permanently stratified tropical reservoir (Borneo). Results showed that horizontal inputs are an important source of both CO2 and CH4 (>90 % of surface emissions) in the upstream reservoir branches. However, this contribution fades along the hydrological continuum, becoming negligible in the main basin of the reservoir, where CO2 and CH4 are uncoupled and driven by different processes. In the main basin, vertical CO2 inputs and sediment CH4 inputs contributed to on average 60 % and 23 % respectively to the surface fluxes of the corresponding gas. Water column metabolism exhibited wide amplitude and range for both gases, making it a highly variable component, but with a large potential to influence surface GHG budgets in either direction. Overall our results show that sources sustaining surface CO2 and CH4 fluxes vary spatially and between the two gases, with internal metabolism acting as a fluctuating but key modulator. However, this study also highlights challenges and knowledge gaps related to estimating ecosystem-scale CO2 and CH4 metabolism, which hinder aquatic GHG flux predictions.

Multivariate statistics for spatial and seasonal quality assessment of water in the Doce River basin, Southeastern Brazil.

This study employed multivariate statistical techniques in one of the main river basins in Brazil, the Doce River basin, to select and evaluate the most representative parameters of the current water quality aspects, and to group the stations according to the similarity of the selected parameters, for both dry and rainy seasons. Data from 63 qualitative monitoring stations, belonging to the Minas Gerais Water Management Institute network were used, considering 38 parameters for the hydrological year 2017/2018. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to reduce the total number of variables and to group stations with similar characteristics, respectively. Using PCA, four principal components were selected as indicators of water quality, explaining the cumulative variance of 68% in the rainy season and 65% in the dry season. The HCA grouped the stations into four groups in the rainy season and three groups in the dry season, showing the influence of seasonality on the grouping of stations. Moreover, the HCA made it possible to differentiate water quality stations located in the headwaters of the basin, in the main river channel, and near urban centers. The results obtained through multivariate statistics proved to be important in understanding the current water quality situation in the basin and can be used to improve the management of water resources because the collection and analysis of all parameters in all monitoring stations require greater availability of financial resources.