Metabolic activity of Planktothrix rubescens and its consequences on oxygen dynamics in laboratory experiment: A stable isotope study.

Fluctuations in dissolved oxygen (DO) contents in natural waters can become intense during cyanobacteria blooms. In a reconnaissance study, we investigated DO concentrations and stable isotope dynamics during a laboratory experiment with the cyanobacterium Planktothrix rubescens in order to obtain insights into primary production under specific conditions. This observation was extended to sub-daily timescales with alternating light and dark phases. Dissolved oxygen concentrations and its isotopes (δ18ODO) ranged from 0.02 to 0.06 mmol · L-1 and from +9.6‰ to +23.4‰. The δ18ODO proved to be more sensitive than concentration measurements in response to metabolic variation and registered earlier shifts to dominance by respiration. Oxygen (O2) contents in the headspace and its isotopes (δ18OO2) ranged from 2.62 to 3.20 mmol · L-1 and from +9.8‰ to +21.9‰. Headspace samples showed less fluctuations in concentration and isotope trends because aquatic processes were hardly able to alter signals once the gas had reached the headspace. Headspace δ18OO2 values were corrected for gas-water equilibration and were determined to be higher than the mean δ18OH2O of -8.7‰. This finding suggests that counteracting respiration was important even during the highest photosynthetic activity. Additionally, headspace analyses led to the definition of a fractionation factor for respiration (αR) of this cyanobacterium with a value of 0.980. This value confirms the one commonly used for cyanobacteria. Our findings may become important for the management of water bodies where decreases in DO are caused by cyanobacteria.

Revealing assembly mechanisms of algal communities in aquatic microniches: Shifts in diversity patterns, microbial interactions and stability along nutrient gradients.

Algal blooms threaten water quality and ecosystem stability in aquatic habitats globally, yet dynamics regulating phytoplankton community assembly, the basis of blooms, remain poorly characterized in small water bodies. Here, we employed high-throughput sequencing to analyze drivers structuring phytoplankton across a trophic gradient of 10 small water bodies over 12 consecutive months. Cyanobacteria and Chlorophyta were identified as potential seed banks priming blooms. Temporal variation in community composition was muted in nutrient-limited waters given Cyanobacteria dominance. Environmental factors and interspecific relationships jointly governed temporal phytoplankton dynamics. Phytoplankton, exhibiting greater sensitivity, responded more rapidly than bacterioplankton to environmental and biological fluctuations. This research provides a robust bench mark characterizing planktonic successional trajectories across small water bodies varying in trophic status. Results reinforce ecological mechanisms underpinning biological control strategies to mitigate algal proliferation and inform water quality management of these ubiquitous aquatic ecosystems.

Distribution characteristics of reactive silicon in six water bodies in the Yangtze River Basin in China.

Terrestrial silicon (Si) from biogeochemically weathered rocks and soils into oceans must pass through several water bodies, resulting in some Si immobilized. Hence, the knowledge on Si distribution characteristics in different water bodies at a basin scale is helpful to understand Si immobilization. A total of 65 surface sediments and corresponding overlying water samples were sampled from six water bodies (Dianchi Lake, DL; Dadu River, DR; Tuojiang River, TR; Honghu Lake, HL; Donghu Lake, DhL; Taihu Lake, TL) in the Yangtze River Basin of China, total dissolved Si (TDSi) in overlying water and exchangeable Si (Ex-Si), active non-biogenic Si (NBSi), and total acid dissolved Si (TADSi) in sediments were analyzed. Water chemical parameters (pH, EC, and TDP) and sediment components (LOI, TN, TP, and TADFe) showed that the water environment characteristics of six water bodies differed. TDSi differed among regions and between lakes and rivers, significantly higher in water bodies in the upper reaches and rivers than the middle or lower reaches and lakes (p < 0.05), respectively. Ex-Si in sediments in the upper reaches was significantly higher than in the middle or lower reaches (p < 0.05), except for DhL, whose Ex-Si was the highest. Mean TADSi and active NBSi were significantly higher in lakes than rivers (p < 0.05). Oxidation of sediments significantly increased TDSi in overlying water and active NBSi in sediments (p < 0.01). Si forms in six water bodies significantly depended on components of the sediments (e.g. active Ca2+, Mg2+, Fe, and Al3+) and water chemical parameters (p < 0.05). Our results suggest that immobilization of Si in water bodies in the Yangtze River Basin depends on the types of water bodies and sediments, lakes and Fe-Al dominated sediments have a high potential to immobilize Si, but anthropogenic interference should not be ignored.

Plummeting toxic contaminates from water through phycoremediation: Mechanism, influencing factors and future outlook to enhance the capacity of living and non-living algae.

Freshwater habitats hold a unique role in the survival of all living organisms and supply water for drinking, irrigation, and life support activities. In recent decades, due to anthropogenic activities, deterioration in the water quality has been a long-lasting problem and challenge to the scientific fraternity. Although, these freshwater bodies have a bearable intrinsic capacity for pollution load however alarming increase in pollution limits the intrinsic capacities and requires additional technological interventions. The release of secondary pollutants from conventional interventions further needs revisiting the existing methodologies and asking for green interventions. Green interventions such as phycoremediation are natural, eco-friendly, economic, and energy-efficient alternatives and provide additional benefits such as nutrient recovery, biofuel production, and valuable secondary metabolites from polluted freshwater bodies. This systemic review in a nut-shell comprises the recent research insights on phycoremediation, technological implications, and influencing factors, and further discusses the associated mechanisms of metal ions biosorption by living and non-living algae, its advantages, and limitations. Besides, the article explores the possibility of future research prospects for applicability at a field scale that will help in the efficient utilization of resources, and improved ecological and health risks.

Bimetallic Cu5Zn8 alloy-embedded hollow porous carbon nanocubes derived from 3D-Cu/ZIF-8 as efficient electrocatalysts for environmental pollutant detection in water bodies.

Excessive use of nitrofurantoin (NFT) and its residues can be harmful to the ecosystem, and to mitigate this, rapid and cost-effective detection of NFT in water bodies is needed. In this regard, we prepared a three-dimensional (3D) copper-zeolitic imidazole framework (Cu/ZIF-8)-derived bimetallic Cu5Zn8 alloy-embedded hollow porous carbon nanocubes (Cu5Zn8/HPCNC) for electrochemical detection of NFT. The resultant material is characterized using suitable spectrophotometry and voltammetry methods. Cu5Zn8/HPCNC is an effective electrocatalyst with high electrical conductivity and a fast electron transfer rate. It also has more catalytic active sites for improved electrochemical reduction of NFT. Fabricated Cu5Zn8/HPCNC-modified screen-printed electrode (SPE) for NFT reduction have a wide linear range with a low detection limit, and high sensitivity (15.343 µA µÐœ-1 cm-2), appreciable anti-interference ability with related nitro compounds, storage stability, reproducibility, and repeatability. Also, the practicability of Cu5Zn8/HPCNC/SPE can be successfully employed in NFT monitoring in water bodies (drinking water, pond water, river water, and tap water) with satisfactory recoveries.

Morphological and molecular identification of lymnaeid snail and trematodes cercariae in different water bodies in Perak, Malaysia.

Lymnaeid snails play a crucial role in the transmission of trematode cercariae as an intermediate host that can infect humans, ruminants like buffalo, and other animals, resulting in serious economic losses. The purpose of the study was to identify the morphological and molecular characteristics of snails and cercariae collected from water bodies near buffalo farms that were integrated with palm oil in Perak, Malaysia. The presence or absence of snails in 35 water bodies was examined via cross-sectional study. From three marsh wetlands, 836 lymnaeid snails were gathered in total. Each snail's shell was morphologically identified to determine its family and species. The cercarial stage inside each snail's body was observed using the crushing method and trematode cercariae types were determined. In addition, the target gene Cytochrome c oxidase subunit 1 (Cox1) and the ribosomal internal transcribed spacer 2 (ITS2) region were used to identify the snail species and cercarial types according to the species level. The findings indicated that the collected snails belong to the family lymnaeidae and Radix rubiginosa species. In snails, the cercarial emergence infection rate was 8.7%. Echinostome, xiphidiocercariae, gymnocephalous, brevifurcate-apharyngeate distome cercariae (BADC), and longifurcate-pharyngeal monostome cercariae (LPMC) are the five morphological cercarial types that were observed. The cercariae were identified using morphological and molecular techniques, and they are members of the four families which are Echinostomatidae, Plagiorchiidae, Fasciolidae, and Schistosomatidae. Interestingly, this is the first study on R. rubiginosa and several trematode cercariae in Perak water bodies near buffalo farms that are integrated with palm oil. In conclusion, our research shown that a variety of parasitic trematodes in Perak use R. rubiginosa as an intermediate host.

Pb(II) Uptake from Polluted Irrigation Water Using Anatase TiO2 Nanoadsorbent.

The adsorption characteristics of titanium dioxide nanoparticles (nano-TiO2) for the removal of Pb(II) from irrigation water were investigated in this work. To accomplish this, several adsorption factors, such as contact time and pH, were tested to assess adsorption efficiencies and mechanisms. Before and after the adsorption experiments, commercial nano-TiO2 was studied using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The outcomes showed that anatase nano-TiO2 was remarkably efficient in cleaning Pb(II) from water, with a removal efficiency of more than 99% after only one hour of contact time at a pH of 6.5. Adsorption isotherms and kinetic adsorption data matched the Langmuir and Sips models quite well, showing that the adsorption process occurred at homogenous sites on the surface of nano-TiO2 by forming a Pb(II) adsorbate monolayer. The XRD and TEM analysis of nano-TiO2 following the adsorption procedure revealed a non-affected single phase (anatase) with crystallite sizes of 9.9 nm and particle sizes of 22.46 nm, respectively. According to the XPS data and analyzed adsorption data, Pb ions accumulated on the surface of nano-TiO2 through a three-step mechanism involving ion exchange and hydrogen bonding mechanisms. Overall, the findings indicate that nano-TiO2 has the potential to be used as an effective and long-lasting mesoporous adsorbent in the treatment and cleaning of Pb(II) from water bodies.

Cyanotoxins in African waterbodies: occurrence, adverse effects, and potential risk to animal and human health.

Public concerns about cyanotoxins production in water and its detrimental impacts on human and animal health are growing primarily due to the widespread eutrophication observed in aquatic ecosystems. A review of relevant literature was done to determine the degree of cyanotoxin occurrence and its harmful effects in African waterbodies. Data were extracted from 64 published studies from 1990 to 2022 that quantified the concentration of cyanotoxins in African aquatic ecosystems. Cyanotoxins have been reported in 95 waterbodies (29 lakes, 41 reservoirs, 10 ponds, 9 rivers, 5 coastal waters, and 1 irrigation canal) from 15 African countries. Cyanotoxins were documented in all the regions of Africa except the central region. Microcystins have been reported in nearly all waterbodies (98.9%), but anatoxin-a (5.3%), cylindrospermopsin (2.1%), nodularins (2.1%), homoanatoxin-a (1.1%), and ß-N-methylamino-L-alanine (1.1%) were encountered in a small number of water ecosystems, homoanatoxin-a and ß-N-methylamino-L-alanine each occurred in one waterbody. The largest concentrations of microcystins and nodularins were reported in South African Lakes Nhlanganzwani (49,410 µg L-1) and Zeekoevlei (347,000 µg g-1). Microcystin concentrations exceeding the WHO guideline for lifetime drinking water (1 µg L-1) were reported in 63% of the aquatic ecosystems surveyed. The most frequently reported toxin-producing cyanobacteria genus is Microcystis spp. (73.7%), followed by Oscillatoria spp. (35.8%) and Dolichospermum spp. (33.7%). Cyanotoxin-related animal mortality and human illness were reported in the continent. Consequently, it is necessary to regularly monitor the level of nutrients, cyanobacteria, and cyanotoxins in African waterbodies in an integrated manner to devise a sustainable water resources management.

Influence of sewage discharge on dissolved oxygen concentration and fish diversity in the Girado stream and Chascomús lake.

Hypoxic aquatic environments have increased in recent decades mainly by human activities that generate pollution. The objective of this work was to study the influence of the discharge of sewage effluents from Chascomús city on the concentration of dissolved oxygen (DO) in the Girado stream and its connection with Chascomús lake and analyze the impact on fish biodiversity. Four sites were selected to measure DO and temperature weekly for one year: discharge of sewage effluent, union of the sewage effluent with the Girado stream, Girado stream and Chascomús lake. Also, ichthyological samplings were carried out in a presumed hypoxic zone and a normoxic zone of the Girado stream. The results showed that there were two hypoxic zones corresponding to the sewage effluent and the union of the effluent with the Girado stream (~3 mg l-1). Also, two normoxic zones were identified, the course of the Girado stream and the union with Chascomús lake (~ 8 mg l-1). In these areas the water temperature varied according to the seasonality of the region (from 10 to 30 °C) without differences between zones. It is important to note that these areas received a constant flow of sewage effluent from Chascomús city (~ 885,600 l per day). In the fish sampling carried out in the 4 seasons of the year, 14 typical species of the Pampas lakes were captured with species more tolerant to low DO. Pejerrey were captured in a small number in both sites but with no signs of abnormalities in the gonads.

Geochemical and isotopic tracers to define the aquifer's vulnerability: the case study of the alluvial multi-aquifer system of the Friulian plain.

The Friuli-Venezia Giulia Region (north of Italy) is characterized by the presence of high-quality freshwater resources which benefit local citizens, animals, environmental habitats, and also agriculture and production activities. Waters from wells, canal, and wastewater selected in the Fiume Veneto area, through a detailed lithological modeling, were sampled and analyzed to characterize them from a geochemical point of view. The chemical and isotopic characterization made it possible to establish provenance, and the average age of water used, making available the estimation of the relationships between recharge capacity and water use in the Fiume Vento area. The focus of this study is to define the average age of the resources based on the time required for the recharge contributions to compensate the losses induced by exploitation. The results made it possible to support the plans for a water balance using the provenance and average age of water sources for the protection of water reserves formed by the multi-aquifer system of the high and medium Friuli plain. The methodology applied has followed the legislation of the water directive considering the overexploitation due to unauthorized withdrawals of the sampling area.

Savanna vegetation increase triggers freshwater community shifts.

Tropical savannas are globally extensive and ecologically invaluable ecosystems. As most ecosystems however, they are subject to serious anthropogenic stress. Defaunation, and especially the loss of large mammals, is pervasive in tropical savannas and known to trigger wide-ranging ecological effects, from vegetation changes to the loss of ecosystem function. Despite what is currently known about the terrestrial consequences of defaunation, and the potential cross-ecosystem influence of large mammals, virtually no research has investigated associated effects on small adjacent water bodies. This research gap persists because (1) tropical savannas have been historically neglected, (2) the ecological value of small water bodies (e.g. ponds) is only recently being recognized, and (3) empirical baseline data are often lacking. In this paper, we compared a rare pre-change dataset with newly collected data on 213 freshwater assemblages, to investigate community structure and composition before and after a major defaunation event. Our research focused on a diverse species assemblage of amphibian larvae (i.e. tadpoles) in temporary savanna ponds. We found that pond vegetation cover increased from 16.0% to 45.6% post-defaunation, that is, a near three-fold increase. Such habitat changes seemed to have benefitted those species that use vegetation during reproduction (e.g. the leaf-folding Afrixalus spp.), while others have declined. Interestingly, we found a strong correlation between tadpole community shifts and other freshwater organisms, which indicates that habitat changes have affected a wide variety of aquatic organisms. Given that organisms inhabiting temporary aquatic habitats often have complex life histories with terrestrial adult life stages, we propose that the terrestrial effects of defaunation have indirectly led to distinct aquatic communities, in addition to direct habitat effects. These results shed new light on the potential role of large-bodied mammals in shaping adjacent ecosystems, and raise important questions concerning the functioning of temporary aquatic systems in the Anthropocene.

Les savanes tropicales sont des écosystèmes étendus à l'échelle mondiale et d'une valeur écologique inestimable, mais qui sont soumis à une pression anthropique croissante. La défaunation, en particulier la perte de grands mammifères, est omniprésente dans les savanes tropicales et pouvant déclencher des effets écologiques de grande envergure allant des changements de végétation à la perte des fonctions écosystémiques. Malgré ce qui est connu des conséquences terrestres de la défaunation, presque aucune recherche n'a étudié les effets de la défaunation sur les plans d'eau temporaires adjacents qui sont utilisés par les grands mammifères. Cette lacune persiste parce que (1) les savanes tropicales ont été historiquement négligées, (2) la valeur écologique des plans d'eau temporaires a souvent été sous-estimée et (3) les données empiriques de référence sont souvent absentes. Dans l'étude présente, nous avons utilisé des données pré/post-défaunation sur 213 assemblages aquatiques de savane, dans le but d'étudier la structure et la composition de ces communités avant et après qu'un événement majeur de défaunation ait eu lieu. Notre recherche se focalise sur des plans d'eau temporaire comptant un nombre important d'espèces de larves d'amphibiens (têtards). Nous avons détecté une multiplication moyenne par près de trois de la couverture végétale des plans d'eau après la défaunation (16,0% à 45,6%). Ces changements d'habitat semblent avoir profité aux espèces qui utilisent la végétation pour leur reproduction (par exemple, Afrixalus spp.), tandis que d'autres espèces avec d'autres préférences d'habitat ont décliné. Nous avons calculé une forte corrélation entre la composition des têtards et celle de leurs prédateurs, ce qui indique que les changements d'habitat ont affecté la plupart des membres de ces communautés aquatiques. Étant donné que les organismes d'habitats aquatiques temporaires ont pour la plupart un cycle biologique complexe figurant à la fois un stade larvaire aquatique et un stade adulte terrestre, nous proposons qu'en plus des effets directs sur l'habitat aquatique (augmentation de la végétation), les effets terrestres de la défaunation ont indirectement altéré les communautés. Ces résultats suggèrent un rôle important des grands mammifères par leur influence sur les écosystèmes aquatique adjacents et soulèvent des questions urgentes concernant la fonctionnalité des systèmes aquatiques temporaires dans l'Anthropocène.

Effects of forest cover on richness of threatened fish species in Japan.

Estuaries--one of the most vulnerable ecosystems globally--face anthropogenic threats, including biodiversity loss and the collapse of sustainable fisheries. Determining the factors contributing to the maintenance of estuarine biodiversity, especially that of fish, is vital for promoting estuarine conservation and sustainability. We used environmental DNA metabarcoding analysis to determine fish species composition in 22 estuaries around Japan and measured watershed-scale land-use factors (e.g., population size, urban area percentage, and forest area percentage). We sought to test the hypothesis that the richness of the most vulnerable estuarine fish species (i.e., registered by the Japanese Ministry of the Environment in the national species red-list) is determined by watershed-scale land-use factors. The richness of such species was greater, where forest cover was highest; thus, forest cover contributes to their conservation. The proportion of agriculture cover was associated with low species richness of red-listed fishes (redundancy analysis, adjusted R2 = 43.9% of total variance, df = 5, F = 5.3843, p = 0.0001). The number of red-listed species increased from 3 to 11 along a watershed land-use gradient ranging from a high proportion of agriculture cover to a large proportion of forest cover. Furthermore, the results showed that throughout Japan all the examined watersheds that were covered by >74.8% forest had more than the average (6.7 species per site) richness of red-listed fish species. This result can be attributed to the already high average forest cover in Japan of 67.2%. Our results demonstrate how the land use of watersheds can affect the coastal sea environment and its biodiversity and suggest that proper forest management in conjunction with land-use management may be of prime importance for threatened fish species and coastal ecosystems in general.

Efectos de la Cobertura Forestal sobre la Riqueza de Especies Amenazadas de Peces en Japón Resumen Los estuarios-uno de los ecosistemas más vulnerables a nivel mundial-enfrentan amenazas causadas por el hombre, incluyendo la pérdida de biodiversidad y el colapso de las pesquerías sustentables. La determinación de los factores que contribuyen al mantenimiento de la biodiversidad estuarina, especialmente la de los peces, es vital para fomentar la conservación y sustentabilidad estuarinas. Usamos un análisis de metasecuenciación de ADN ambiental para determinar la composición de especies de peces en 22 estuarios de Japón y medimos los factores del uso de suelo a nivel de cuenca (p. ej.: tamaño poblacional, porcentaje de área urbana y porcentaje de área forestal). Buscamos probar la hipótesis de que la riqueza de las especies de peces más vulnerables (es decir, aquellas registradas por el Ministerio Japonés del Ambiente en la lista roja de especies a nivel nacional) está determinada por los factores de uso de suelo a nivel de cuenca. La riqueza de dichas especies fue mayor en donde la cobertura forestal era la más alta; por lo tanto, la cobertura forestal contribuye a la conservación de estas especies. La proporción de la cobertura agrícola estuvo asociada con una baja riqueza de especies de peces en la lista roja (análisis de redundancia, R2 ajustada = 43.9% de la varianza total, gl = 5, F = 5.3843, p = 0.0001). El número de especies en la lista roja incrementó de 3 a 11 a lo largo del gradiente de uso de suelo de la cuenca, yendo desde una proporción alta de cobertura agrícola a una proporción alta de cobertura forestal. Además, los resultados mostraron que, en Japón, todas las cuencas analizadas que contaban con una cobertura forestal >74.8% tenían mayor riqueza de especies de peces en la lista roja que el promedio (6.7 especies por sitio). Este resultado puede atribuirse a la ya de por sí elevada cobertura forestal de Japón (67.2%). Nuestros resultados demuestran cómo el uso de las cuencas puede afectar al ambiente costero marino y a su biodiversidad y sugiere que la gestión adecuada de los bosques en conjunto con el manejo del uso de suelo puede ser de suma importancia para las especies amenazadas de peces y los ecosistemas costeros en general.

Copper accumulation in the aquatic fern Salvinia minima causes more severe physiological stress than zinc.

Copper (Cu) and zinc (Zn) have a high demand in the industry. However, these ions, at high concentrations, can cause severe damage to both fauna and flora. Phytoremediation has gained international importance because its relatively low cost and it is environmentally friendly. The aim of the present study was to evaluate the capacity of Salvinia minima of accumulating Cu and Zn from aqueous solutions of various external concentrations (20, 40 and 80 µmol L-1 of CuSO4 and ZnSO4, separately). In addition, to estimate the effect of exposure of S. minima plants to those metals, on various physiological parameters (growth potential, maximum quantum efficiency of PSII, electrolyte leakage: as a cell membrane integrity index). S. minima was able of accumulating more Zn than Cu in its tissues, reaching values of 6.96 mg Cu g-1 dry weight (DW) and 19.6 mg Zn g-1 DW when exposed to 80 µM of each metal during 96 h, that were stored mainly at roots. Despite accumulating less Cu in its tissues, Cu had more severe reductions in various physiological parameters than Zn (in maximum quantum efficiency, integrity of cell membranes, and growth). We conclude that this species can be useful in the phytoremediation for copper and zinc in relatively short time, as maximum accumulation occurred within the first 24 h. However, in the long term, the accumulation of such metals is accompanied by a negative impact in the appearance, physiology, and growth of this plant species, which was more severe for copper exposure than for zinc.

Inland water bodies in China: Features discovered in the long-term satellite data.

Water bodies (WBs), such as lakes, ponds, and impoundments, provide essential ecosystem services for human society, yet their characteristics and changes over large areas remain elusive. Here we used unprecedented data layers derived from all Landsat images available between 1984 and 2015 to understand the overall characteristics and changes of WBs between 2 epochs (i.e., 1984 to 1999 and 2000 to 2015) in China. Results show that the abundance estimate of WBs greater than 1 km2 and the total WB surface area were 0.3 to 1.5 times and 0.2 to 0.5 times more than the previous estimates, respectively. The size-abundance and shoreline-area relationships of WBs in China conformed to the classic power scaling law, in contradiction to most previous studies. WB changes with various occurrence probabilities show widespread coexistence of disappearance of existent and emergence of new WBs across China driven primarily by human activities and climate change. Our results highlight the importance of using appropriate long-term satellite data to reveal the true properties and dynamics of WBs over large areas, which is essential for developing scaling theories and understanding the relative impacts of human activities and climate change on water resources in the world.

In-situ rapid monitoring of nitrate in urban water bodies using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) coupled with deconvolution algorithm.

Urban river and lake systems show important ecological function, and eutrophication frequently occurs and results from human activities due to the limited self-regulating ability. Since nitrate (NO3-) is one of the key factors causing water eutrophication, its rapid qualification plays critical role in the eutrophication control and management. In this study, water samples were collected from typical water bodies from Nanjing in different seasons, and Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) was employed for the quantitative determination of NO3- coupled with algorithms of deconvolution and partial least squares regression (PLSR). Results indicated that the typical absorption band of NO3- at 1500-1200 cm-1 was observed and the intensity of the band around 1360 cm-1 was positively correlated with the concentration of NO3- through spectra deconvolution. PLSR models were established based on the deconvolution spectra, which were excellent with the correlation coefficients (R2) of more than 0.8886 and the ratio of prediction to deviation (RPD) of more than 2.76; it was found that the carbonate in water might impact the prediction due to its absorption around 1450 cm-1, but the prediction model performed well in condition that the carbonate content in a low level with less than 10 mg L-1. Significant temporal and spatial variations of NO3- were observed in the typical water bodies, and the Qinhuai River having the highest NO3- content, which mainly was influenced by human activities, and the impact of water pH and temperature were not significantly observed. Therefore, FTIR-ATR combined with deconvolution and PLSR, allowed a rapid determination of NO3- in urban water bodies, providing an alternative option for the monitoring of nitrate in natural water body, which will benefit the prevention and control of eutrophication.

Assessment of spatial-temporal changes in water bodies and its influencing factors using remote sensing and GIS - a model study in the southeast coast of India.

Concerns have been raised about the threat of ecological imbalance due to the loss of water bodies in densely populated areas. The present study explored the changes in water bodies in terms of area, number, and size in northern districts of Tamil Nadu, India, between 1978 and 2018 using satellite data, geographic information system, spatial analysis, ground truth verification, and field validation. The analysis indicated that the water bodies' area has reduced by 3027 ha and 4363 ha in the Kancheepuram and Tiruvallur Districts, respectively. Almost 179 water bodies have entirely disappeared, and 628 water bodies have been partly converted for other purposes. Of the disappeared water bodies, small, medium, and large water bodies account for 53, 93, and 33, respectively. The main reason for the changes in water bodies was the conversion to agriculture and buildings. Overall, the water bodies' area and number have been reduced by 9% and 12%, respectively, while the population has grown by 37%. The water bodies lost due to anthropogenic activities demand the scientific inventory of water bodies and integrated water resources management at a state or national level with strict monitoring regulations to protect them.

Assessing the status of changing regimes of water bodies in Gorakhpur District, Uttar Pradesh, India.

Water bodies play a very important role in maintaining and restoring the ecological balance, but they are one of the most threatened habitats in the world. Anthropogenic intervention is changing the regimes of wetlands almost everywhere particularly in the developing countries. Gorakhpur District is dotted with many big and small flood plain-related water bodies like rivers, streams, tanks, dead arms, oxbow lakes, etc. Some of these water bodies are worst affected and are degraded by encroachment for agriculture and other economic and developmental activities. Channel migration, aggravated by human intervention, on alluvial plain is also very frequent, which has direct impact on the nature of water bodies and land use transformations of the region. In this paper, the authors have made an attempt to (a) bring current geographical and historical background of water bodies/wetlands for the district. It aims to assess long-term (1917-2018) and short-term (pre- and post-monsoon) changes in the water bodies of Gorakhpur District; (b) provide changes in the regime of water bodies/wetlands and their conversion to different types of land use/land cover classes due to human intervention and due to annual rainy season, which inundates a large extent of the area every year; (C) assess the channel characteristics and morphometric analysis of main rivers of the region during the last hundred years. Remote sensing and Geographical Information System (GIS) have been used to prepare the inventory and to perform change detection, using land use/land cover maps. The floodplain areas of water bodies have almost changed their morphological characters due to encroachment by the nearby areas. Canals, drainage channels, and lakes are the most affected water bodies in the region, which have recorded - 65.38% and 43.37% loss in their area. Even permanent rivers have recorded a decrease of - 16.96% in the area. As per the seasonal change, agriculture land suffered the greatest conversion (18.33%) due to floodwater inundation. The study provides a platform to planners to chalk out their policies and also for monitoring the water bodies. Furthermore, analysis on channel migration will help predict the future course of the main rivers.

Temporal dynamics of trematode intermediate snail host environmental DNA in small water body habitats.

Environmental DNA (eDNA) surveying has potential to become a powerful tool for sustainable parasite control. As trematode parasites require an intermediate snail host that is often aquatic or amphibious to fulfil their lifecycle, water-based eDNA analyses can be used to screen habitats for the presence of snail hosts and identify trematode infection risk areas. The aim of this study was to identify climatic and environmental factors associated with the detection of Galba truncatula eDNA. Fourteen potential G. truncatula habitats on two farms were surveyed over a 9-month period, with eDNA detected using a filter capture, extraction and PCR protocol with data analysed using a generalized estimation equation. The probability of detecting G. truncatula eDNA increased in habitats where snails were visually detected, as temperature increased, and as water pH decreased (P < 0.05). Rainfall was positively associated with eDNA detection in watercourse habitats on farm A, but negatively associated with eDNA detection in watercourse habitats on farm B (P < 0.001), which may be explained by differences in watercourse gradient. This study is the first to identify factors associated with trematode intermediate snail host eDNA detection. These factors should be considered in standardized protocols to evaluate the results of future eDNA surveys.

Variations, health risks, pollution status and possible sources of dissolved toxic metal(loid)s in stagnant water bodies located in an intensive agricultural region of Turkey.

There are many reservoirs, ponds and lakes in the Meriç-Ergene River Basin (Turkey), which is an intensive agricultural region. Since agrochemicals are extensively applied to the agricultural soils in the basin, these water bodies may be contaminated with toxic metal (loid)s (TMs). However, no study has been conducted to determine TM levels in the water bodies. In this study, levels of seven TMs (Cr, As, Cu, N, Zn, Cd and Pb) in surface water samples taken from 25 different stagnant water bodies (11 reservoirs, 12 ponds and 2 lakes) in the dry and wet seasons were measured and compared with water quality guidelines. In addition, spatial and seasonal variations, health risks, pollution status and possible sources of TMs were assessed. The mean As concentration of the lakes was significantly higher due to drainage water from paddy fields. The ponds had higher total mean TM concentration likely due to their low water volume. Surface runoff from rainfall caused the Cr, Zn, Cd, Pb and Cu concentrations to increase in the wet season. Only the mean As concentration of the lakes in the dry season was above the drinking water standards. Metal pollution indices showed low contamination of the water bodies in both seasons. Health risk indices indicated that As in the lakes in the dry season via ingestion exposure pathway may pose both non-carcinogenic and carcinogenic health risks to the residents. The results of factor and correlation analyses showed that among the studied TMs, only As originated from anthropogenic sources. The findings of this study revealed that agricultural activities caused As pollution in the lakes, while the reservoirs and ponds were not significantly affected by agricultural activities. We suggest that the levels of TMs in all water bodies should be measured at regular intervals to check the quality of surface water.

Estimation of Infiltration Volumes and Rates in Seasonally Water-Filled Topographic Depressions Based on Remote-Sensing Time Series.

In semi-arid ecoregions of temperate zones, focused snowmelt water infiltration in topographic depressions is a key, but imperfectly understood, groundwater recharge mechanism. Routine monitoring is precluded by the abundance of depressions. We have used remote-sensing data to construct mass balances and estimate volumes of temporary ponds in the Tambov area of Russia. First, small water bodies were automatically recognized in each of a time series of high-resolution Planet Labs images taken in April and May 2021 by object-oriented supervised classification. A training set of water pixels defined in one of the latest images using a small unmanned aerial vehicle enabled high-confidence predictions of water pixels in the earlier images (Cohen's Κ = 0.99). A digital elevation model was used to estimate the ponds' water volumes, which decreased with time following a negative exponential equation. The power of the exponent did not systematically depend on the pond size. With adjustment for estimates of daily Penman evaporation, function-based interpolation of the water bodies' areas and volumes allowed calculation of daily infiltration into the depression beds. The infiltration was maximal (5-40 mm/day) at onset of spring and decreased with time during the study period. Use of the spatially variable infiltration rates improved steady-state shallow groundwater simulations.