Various Types Of Water Bodies Research Articles

Colour range of euglenoid (Euglenophyceae) blooms

The presence of autotrophs, heterotrophs and mixotrophs among euglenoid taxa, multiple means of nutrition, and high tolerance to a wide range of thermal living conditions contribute to their colonization of various types of water bodies in different climatic zones. The formation of water “blooms” by euglenoids occurs during accelerated development and intensive cell division of these organisms. Euglenoids outcompete other microalgae and produce significant biomass under favorable conditions. The ability to produce temporal, reproductive and protective cysts also contributes to rapid bloom formations. Our observations suggest that their features probably make them model organisms for observing environmental changes in small water bodies. So far, little attention has been given to the species-dependent color variation of euglenoid blooms. Long-time research on euglenoid taxonomy, biogeography and habitat observations allow observers to recognize different blooms depending on the species causing the phenomenon: Euglena sanguinea, E. mutabilis, E. clara, E. hemichromata, E. geniculata, E. agilis, Euglenaria anabaena, Euglenaformis chlorophoenica, Monomorphina pyrum, Phacus pleuronectes, Ph. orbicularis, Lepocinclis ovum, Trachelomonas volvocina, T. volvocinopsis and T. caudata. The color range of euglenoid blooms are presented here for the first time.

Biodiversity of autotrophic euglenids based on the group specific DNA metabarcoding approach

This study reports a comprehensive analysis of photoautotrophic euglenids’ distribution and biodiversity in 16 small water bodies of various types (including fish ponds, field ponds, rural ponds and park ponds) located in three regions of Poland: Masovia, Masuria and Pomerania during a period of three years. By employing a euglenid specific barcode marker and a curated database of V2 18S rDNA sequences it was possible to identify 97.7 % of euglenid reads at species level. A total of 152 species classified in 13 genera were identified. The number of euglenid species found in one pond varied from 40 to 102. The most common species were Euglena agilis and Euglenaria caudata, found in every analysed waterbody. The highest number of observed species belonged to Trachelomonas and Phacus. Certain species exhibited a tendency to coexist, suggesting the presence of distinct species assemblages. Among them, the most distinctive cluster was associated with water bodies located in the Masuria region, characterized also by the greatest species richness, including many very rare species: Euglenaformis chlorophoenicea, Lepocinclis autumnalis, L. marssonii, Trachelomonas eurystoma, T. manschurica, T. mucosa, T. zuberi, T. zuberi var. nepos.

Leeches (Annelida, Hirudinea) Fauna of Nakhchivan Autonomous Republic

The fauna of the leeches of Nakhchivan Autonomous Republic is represented by 10 species belonging to 9 genera, 5 families, 2 orders and one class. According to zoogeographical affiliation, leech species belong to 4 faunistic complexes. In the benthic infauna of various types of water bodies, glossyphonides predominate in the frequency of occurrence and abundance of individuals. An extremely rare medical leech (Hirudo medicinalis) is the only practically useful representative of the girudofauna. Functional significance of other species in biocenoses is low. The article also presents data on morphology, body sizes, objects of finding and biotopes of leeches of fauna of Nakhchivan.

Ecological assessment of eutrofication of lakes in «Shatskyі» biosphere reserve

The natural process of eutrophication of hydroecosystems is determined by many factors and is mostly long-term, almost irreversible. In the 20th and 21st centuries. Accelerated anthropogenic eutrophication of many waters took place, in particular the lakes of Shatsky group (Shatskyi National Natural Park, Volyn Region, Ukraine). Changes in water due to their enrichment with biogenic substances and chemical compounds accompany the increase in plant productivity and may be the result of «natural aging», anthropogenic influence, organic pollution. One of the concepts of the succession of lake ecosystems assumes that lakes go through different stages of trophicity (nutrition), starting with oligotrophy or dystrophy. The last stage (climax) of the successional series is intensive eutrophication, during which the lake is partially replaced by a swamp and, in the end, can become a dry land, meadow, shrub or forest vegetation. Eutrophication of lake ecosystems is accompanied by a change in transparency, chlorophyll a concentration, and oxygen concentration. An active phase of eutrophication of the limnoecosystems of Shatskyi biosphere reserve has been established. On the territory of the latter there are rivers and streams with a constant water flow, more than 114 km long, and also includes 31 lakes. The results of ecological studies of various types of water bodies of Shatsky Lakes, which were carried out in 2016–2020, are presented. The performed typification of Shatsky Lakes by the area of the water mirror proved that there are no very large lakes here, there are three large lakes (Svityaz, Pulemetske, Luky-Peremut). The analysis of the nature-reserved territory of Western Polissia proved that special attention should be paid to lakes of small and small sizes, as well as medium and shallow lakes (Lynovets, Somynets, Buzhnya Bay, etc.), which are not capable of active self-regulation. The optimal mechanism for monitoring the ecological state of water bodies (lakes) using the remote sensing method is proposed.

Ecology of testate amoebae in waterbodies of the Central Highlands and South-Central Coast provinces of Vietnam with the description of new species Difflugia quangtrani sp. nov.

This study provides new data on ecology of testate amoebae in the waterbodies of the Central Highlands and South-Central Coast regions of Vietnam. A total of 108 species and subspecies including six new records for Vietnam were identified. One new species Difflugia quangtrani sp. nov. was described. Difflugia, Arcella, and Centropyxis were the most species-rich genera, and Centropyxis aculeata was the most common species. The results of NMDS and ANOSIM analyses for the first time showed significant differences in composition of tropical freshwater testate amoeba communities within both various types of waterbodies (reservoir, river, and wetland) and biotopes (plankton and benthos). Average species richness per sample in different types of waterbodies was similar, while that of plankton was statistically higher than in benthos. The distance decay of similarity in tropical freshwater testate amoeba community of both plankton and benthos was observed for the first time indicating the importance of geographical distance in testacean species composition changes between samples. Redundancy analyses followed by the forward selection have determined elevation, pH, and dissolved oxygen as significant factors that affect tropical freshwater testacean community. More large-scale climatic and small-scale hydrological and hydrochemical variables should be included into further studies to find out most important factors determining structure of freshwater testacean assemblages.

Historical Global Review of Acid-Volatile Sulfide Sediment Monitoring Data

Acid-volatile sulfides (AVS) are strongly associated with the bioavailability of some divalent metals such as cadmium, copper, lead, nickel and zinc. However, the global spatial variability of AVS for aquatic systems is unknown. The specific goals of this study were to: (1) summarize all available AVS monitoring data from all types of freshwater and saltwater waterbodies (streams/creeks, rivers, lakes/ponds/reservoirs and estuarine/marine areas) and (2) compare AVS concentrations from these various types of waterbodies considering both soil type classification and biomes. AVS measurements were reported from 21 different countries. A total of 17 different soil types were reported for all waterbody types and both podzols and luvisols were found in all waterbody types. Nine different biomes were sampled for all waterbody types. The temperate broadleaf and mixed forest biome was sampled for AVS in all waterbody types. Mean AVS concentrations ranged from 0.01 to 503 µmoles/g for 140 different waterbody types and the 90th centile for all these waterbodies was 49.4 µmoles/g. A ranking of waterbody type means from low to high AVS measurements showed the lowest mean value was reported for streams/creeks (5.12 µmoles/g; range from 0.1 to 39.8 µmoles/g) followed by lakes/ponds/reservoirs (11.3 µmoles/g; range from 0.79 to 127 µmoles/g); estuarine/marine areas (27.2 µmoles/g; range from 0.06 to 503 µmoles/g) and rivers (27.7 µmoles/g; range from 1.13 to 197 µmoles/g). The data provided in this study are compelling as it showed that the high variability of AVS measurements within each waterbody type as well as the variability of AVS within specific locations were often multiple orders of magnitude differences for concentration ranges. Therefore, a comprehensive spatial and temporal scale sampling of AVS in concert with divalent metals analysis is critical to avoid possible errors when evaluating the potential ecological risk of divalent metals in sediment.

Life cycle of Bilharziella polonica (Trematoda, Schistosomatidae) parasite of semi-aquatic birds in Uzbekistan

Schistosomatidae are an actively studied ecological group of trematodes. Their ability to cause various parasitic diseases in animals and humans makes them an interesting object of study for a number of research centres worldwide. One of the commonest species in this group is Bilharziella polonica (Kowalewsky, 1895), whose mature stages have been recorded in aquatic and semi-aquatic birds in Uzbekistan. Our research team established that the following birds were infected with mature trematodes B. polonica: Anas platyrhynchos (23%), A. crecca (18%), Podiceps ruficollis (11%), Ardea cinerea (14%) and one individual of Oxyura leucocephala. The highest infection rate was shown by the mallard A. platyrhynchos (23%) and common teal A. crecca (18%). The infection intensity ranged between 2 and 27 individuals. Research into various types of water bodies in Karakalpakstan identified 10 mollusc species – Lymnaeidae (4 species), Planorbidae (4 species) and Physidae (2 species). Cercariae morphologically similar to larvae of B. polonica were found in two species, Planorbis planorbis and P. tangitarensis. 6 chicks of domestic ducks were experimentally infected with those cercariae to track the life cycle of B. polonica in the organism of a definitive host. Helmintholological dissections showed that every duck was infected with B. polonica, which became mature 23–27 days after the infection. Eggs of B. polonica were recorded in the excrement of one of the birds 33–35 days after the infection. Based on field and experimental research, we identify the mollusc P. tangitarensis as a new intermediate host for B. polonica in Uzbekistan.

A New Lightweight Convolutional Neural Network for Multi-Scale Land Surface Water Extraction from GaoFen-1D Satellite Images

Mapping land surface water automatically and accurately is closely related to human activity, biological reproduction, and the ecological environment. High spatial resolution remote sensing image (HSRRSI) data provide extensive details for land surface water and gives reliable data support for the accurate extraction of land surface water information. The convolutional neural network (CNN), widely applied in semantic segmentation, provides an automatic extraction method in land surface water information. This paper proposes a new lightweight CNN named Lightweight Multi-Scale Land Surface Water Extraction Network (LMSWENet) to extract the land surface water information based on GaoFen-1D satellite data of Wuhan, Hubei Province, China. To verify the superiority of LMSWENet, we compared the efficiency and water extraction accuracy with four mainstream CNNs (DeeplabV3+, FCN, PSPNet, and UNet) using quantitative comparison and visual comparison. Furthermore, we used LMSWENet to extract land surface water information of Wuhan on a large scale and produced the land surface water map of Wuhan for 2020 (LSWMWH-2020) with 2m spatial resolution. Random and equidistant validation points verified the mapping accuracy of LSWMWH-2020. The results are summarized as follows: (1) Compared with the other four CNNs, LMSWENet has a lightweight structure, significantly reducing the algorithm complexity and training time. (2) LMSWENet has a good performance in extracting various types of water bodies and suppressing noises because it introduces channel and spatial attention mechanisms and combines features from multiple scales. The result of land surface water extraction demonstrates that the performance of LMSWENet exceeds that of the other four CNNs. (3) LMSWENet can meet the requirement of high-precision mapping on a large scale. LSWMWH-2020 can clearly show the significant lakes, river networks, and small ponds in Wuhan with high mapping accuracy.

Temporal Stability of Phytoplankton Functional Groups Within Two Agricultural Irrigation Ponds in Maryland, USA

Phytoplankton functional groups and their influence on water quality have been studied in various types of water bodies but have yet to be studied in agricultural irrigation ponds. Freshwater sources (e.g., lakes, rivers, and reservoirs) have been previously shown to exhibit high spatial and temporal variability in phytoplankton populations. Improvements in the monitoring of phytoplankton populations may be achieved if patterns of stable spatial variability can be found in the phytoplankton populations through time. The objective of this work was to determine if temporally stable spatial patterns in phytoplankton communities could be detected in agricultural irrigation ponds using a functional group approach. The study was performed at two working agricultural irrigation ponds located in Maryland, USA over two summer sampling campaigns in 2017 and 2018. Concentrations of four phytoplankton groups, along with sensor-based and fluorometer based water quality parameters were measured. Temporal stability was assessed using mean relative differences between measurements in each location and averaged measurements across ponds on each sampling date. Temporally stable spatial patterns of three phytoplankton functional groups were found for both ponds over the two sampling seasons. Both ponds had locations where specific phytoplankton functional group concentrations were consistently higher or lower than the pond's average concentration for each sampling date. Zones of consistently higher or lower than average concentrations were associated with flow conditions, pond morphology, and human activities. The existence of temporally stable patterns of phytoplankton functional group concentrations can affect the outcome of a water quality assessment and should be considered in water quality monitoring designs.

Freezing: how do water mites (Acari: Hydrachnidia) survive exposure to sub-zero temperatures?

Until now, very little is known about the ability of adult and deutonymph water mites (Acari, Hydrachnidia) to survive in sub-zero temperatures. Information concerns mainly water mites from vernal astatic waters, and the knowledge has never been experimentally verified. To determine the sensitivity of water mites to freezing, experiments were conducted on (1) the impact of acclimatization, (2) temperature, and (3) duration of freezing on survival, (4) the survival rate of water mites from various types of water bodies, and (5) the survival rate of water mites from different climatic zones. The experiments were carried out in a phytotron chamber, and water mites were placed in containers (10 × 10 × 5 cm) filled with 4/5 of water for 10 specimens each. Water mites were identified to the species level after finishing the experiments. The temperature was lowered 1 °C every hour until the target temperature was reached. After a certain period of freezing (depending on the treatment) the temperature was raised by 1 °C every hour until it reached 4 °C. The time of the experiment was measured from the moment the desired temperature was reached (below 0 °C) until the ice thawed and the temperature of 4 °C was reached again. The highest survival rates had Limnochares aquatica, Piona nodata, Sperchon clupeifer and Lebertia porosa, followed by L. insignis, Hygrobates longipalpis, H. setosus, Limnesia undulatoides, Piona pusilla, Arrenurus globator, Hydrodroma despiciens, Piona longipalpis, Sperchonopsis verrucosa, Unionicola crassipes and Mideopsis crassipes; no specimens of Torrenticola amplexa survived. The following conclusions were drawn: (1) water mites can survive freezing to −2 °C, lower temperatures are lethal for them; (2) they survived better the short period of freezing (24–48 h) than the long period (168 h); (3) resistance to freezing seems to be an evolutionary trait of individual species, only partly related to the living environment; and (4) freezing survival rates are linked to the region of Europe and are much lower in Southern than in Central Europe.

Accurate extraction of surface water in complex environment based on Google Earth Engine and Sentinel-2.

To realize the accurate extraction of surface water in complex environment, this study takes Sri Lanka as the study area owing to the complex geography and various types of water bodies. Based on Google Earth engine and Sentinel-2 images, an automatic water extraction model in complex environment(AWECE) was developed. The accuracy of water extraction by AWECE, NDWI, MNDWI and the revised version of multi-spectral water index (MuWI-R) models was evaluated from visual interpretation and quantitative analysis. The results show that the AWECE model could significantly improve the accuracy of water extraction in complex environment, with an overall accuracy of 97.16%, and an extremely low omission error (0.74%) and commission error (2.35%). The AEWCE model could effectively avoid the influence of cloud shadow, mountain shadow and paddy soil on water extraction accuracy. The model can be widely applied in cloudy, mountainous and other areas with complex environments, which has important practical significance for water resources investigation, monitoring and protection.

Morphological characteristics of Kellicottia bostoniensis (Rousselet, 1908) (Rotifera: Brachionidae) in water bodies of the Middle Volga basin

The morphological characteristics of the North American invasive species Kellicottia bostoniensis Rousselet, 1908 were studied in 29 various types of water bodies and watercourses of the Middle Volga basin. The water bodies, which are the habitats of K. bostoniensis, are located on several territories that differ significantly in a set of characteristics, such as their geological structure, relief, climate, anthropogenic impact, hydrochemical and hydrophysical indicators, etc. The sizes of K. bostoniensis individuals in most of the studied water bodies and watercourses were measured and analyzed for the first time. A high positive correlation was found between the total body length and the posterior spine length (R2 = 0.79, p < 0.01), as well as the anterior spine length (R2 = 0.75, p < 0.01). A relationship was revealed between the lengths of the anterior and posterior spines (R2 = 0.58, p < 0.01). K. bostoniensis individuals in the studied water bodies and watercourses are characterized by large sizes, the median values of the total body length being 236–440 μm. These sizes are similar to those of individuals in the native habitats of North America and some biotopes of Europe and European Russia. Among the previously studied water bodies of Russia and other countries (Belarus, Sweden, Finland, Brazil, and Argentina), where researches of the morphological variability of K. bostoniensis were carried out, the largest body sizes were characteristic for the invader species of the Sura River. Larger K. bostoniensis specimens live in deep mesotrophic water bodies with high transparency, compared with representatives of this species in shallow eutrophic water bodies with less transparency in the Middle Volga basin. Our data on the morphological characteristics of the invading species of water bodies in the Middle Volga basin significantly expand the existing information on the morphological variability of K. bostoniensis individuals and their dependence on environmental factors.

Intensity of Phytoplankton Primary Production in Urban Water Bodies of Various Types

Intensity of Phytoplankton Primary Production in Urban Water Bodies of Various Types

The current state of macrozoobenthos of some small reservoirs the North Kazakhstan region

Awareness of ecosystem integrity increases the relevance of collecting information on the biodiversity of water bodies of various types. The episodic nature of studies of small water bodies, along with the high variability of their hydrological, hydrochemical, and morphometric parameters, is the reason for the lack of a full assessment of the state of biota. The current paper provides information on macrozoobenthos of four small water bodies in the North Kazakhstan region. The study revealed 59 representatives with a predominance of insects in the benthofauna. Bottom complexes of shallow temporary water bodies were characterized by a wider spectrum with a greater proportion of insects relative to similar variables for lake Big Koskol. The basis was composed by species adapted to fluctuations of water availability, which led to a relatively stable state of biocenoses against the background of a significant range of quantitative characteristics of zoobenthos. More abundant development of benthic invertebrates highlighted in the lake Bolshoy Koskol (with the dominance of amphipods) and in the temporary water body T26 (with the predominance of insects). By the size of the average annual zoobenthos biomass — 29–31.5 g / m2 — the mentioned above water bodies were classified as highly productive. The level of development of benthic organisms in water bodies T20–T14, where Vermes were the leaders in biomass assessed as increased productive and moderate productive (10.3–3.1 g/m2 respectively). A low faunistic similarity of macrozoobenthos was noted, indicating the originality of the benthic complexes of the studied water body, which once again emphasizes the role of small water body in maintaining the biodiversity of the ecosystem. Relatively high structural variables of benthocenoses indicate a stable ecological state of bottom communities. The abundance of zoobenthos creates the prerequisites for the utilization of the studied and similar water bodies for organizing amateur — sport fishery and the extraction of feed used in aquarium fish farming

A Multi-Scale Water Extraction Convolutional Neural Network (MWEN) Method for GaoFen-1 Remote Sensing Images

Automatic water body extraction method is important for monitoring floods, droughts, and water resources. In this study, a new semantic segmentation convolutional neural network named the multi-scale water extraction convolutional neural network (MWEN) is proposed to automatically extract water bodies from GaoFen-1 (GF-1) remote sensing images. Three convolutional neural networks for semantic segmentation (fully convolutional network (FCN), Unet, and Deeplab V3+) are employed to compare with the water bodies extraction performance of MWEN. Visual comparison and five evaluation metrics are used to evaluate the performance of these convolutional neural networks (CNNs). The results show the following. (1) The results of water body extraction in multiple scenes using the MWEN are better than those of the other comparison methods based on the indicators. (2) The MWEN method has the capability to accurately extract various types of water bodies, such as urban water bodies, open ponds, and plateau lakes. (3) By fusing features extracted at different scales, the MWEN has the capability to extract water bodies with different sizes and suppress noise, such as building shadows and highways. Therefore, MWEN is a robust water extraction algorithm for GaoFen-1 satellite images and has the potential to conduct water body mapping with multisource high-resolution satellite remote sensing data.

A review of methods for measuring groundwater–surface water exchange in braided rivers

Abstract. Braided rivers, while uncommon internationally, are significant in terms of their unique ecosystems and as vital freshwater resources at locations where they occur. With an increasing awareness of the connected nature of surface water and groundwater, there have been many studies examining groundwater–surface water exchange in various types of waterbodies, but significantly less research has been conducted in braided rivers. Thus, there is currently limited understanding of how characteristics unique to braided rivers, such as channel shifting, expanding and narrowing margins, and a high degree of heterogeneity affect groundwater–surface water flow paths. This article provides an overview of characteristics specific to braided rivers, including a map showing the regions where braided rivers are mainly found at the global scale: Alaska, Canada, the Japanese and European Alps, the Himalayas, Russia, and New Zealand. To the authors' knowledge, this is the first map of its kind. This is followed by a review of prior studies that have investigated groundwater–surface water interactions in braided rivers and their associated aquifers. The various methods used to characterise these processes are discussed with emphasis on their effectiveness in achieving the studies' objectives and their applicability in braided rivers. We also discuss additional methods that appear promising to apply in braided river settings. The aim is to provide guidance on methodologies most suitable for future work in braided rivers. In many cases, previous studies found a multi-method approach useful to produce more robust results and compare data collected at various scales. Given the challenges of working directly in braided rivers, there is considerable scope for the increased use of remote sensing techniques. There is also opportunity for new approaches to modelling braided rivers using integrated techniques that incorporate the complex river bed terrain and geomorphology of braided rivers explicitly. We also identify a critical need to improve the conceptual understanding of hyporheic exchange in braided rivers, rates of recharge to and from braided rivers, and historical patterns of dry and low-flow periods in these rivers.

Effects of temperature and water levels on dynamics of density and structure of the fish population of the channel-floodplain complex of a large river in the period of spring floods

The article discusses the features of the dynamic process of migration of ichthyofauna from wintering sites to the wetlands of a large boreal river for feeding and spawning. The influence of factors of temperature and water level on various groups of fish is estimated, and the role of water bodies of various types during fish migration in a flooded floodplain is also established. The research was performed during the spring flood in the floodplain-channel complex of the Irtysh River (Western Siberia, Russian Federation) in the water area of the conjugate water bodies: the lotic and lentic parts of the riverbed depression and the mouth of the tributary – transit section of the migration pathway of fish to the flooded floodplain. The research work was performed by “AsCor” – computerized hydroacoustic complex, hydroacoustic survey data were processed in the laboratory. The “AsCor” complex remotely performs taxonomic identification of abundant species of fish at the family level by groups (Cyprinidae, Percidae, Coregonidae–Esocidae, Acipenseridae–Lotidae). It was found that after the breakup of ice cover, maximum densities of fish were observed in the wintering sections – the initial location of the spring migration. During the 30-days observation period in the wintering sections and conjugate water bodies, the density of fish decreased from 4 to 13 times due to their migration to the floodplain. The response to a decrease in the overall density of fish in the year-round functioning lotic part of the riverbed depression to the influence of factors of water level and temperature regimes was >0.300 in general for ichthyofauna and for all groups of fish registered by hydroacoustic method (Cyprinidae, Percidae, Coregonidae–Esocidae, Acipenseridae–Lotidae). We constructed regression models of changes in the density of fish in the wintering sections of the river depending on the considered factors. Use of ANOVA analysis of variance confirmed the adequacy of the choice and the acceptability of the constructed models. We established a high statistically significant inverse correlation between the density of the fish, the water level and temperature regime for the mouth of the Konda River and the lentic part of the riverbed depression, which are transit sections of the migration pathway of fish in the floodplain. The lentic part of the riverbed depression may perform the function of a temporary station of fish during migration to the floodplain, which is beneficial from the point of view of bioenergetics resources. During the observation period, in the river flows there was a decrease in the proportion of larger fish and an increase in smaller individuals; in the lentic part of the riverbed depression, on the contrary, there was a reduced proportion of small fish and increase in the proportion of larger individuals.This pattern is explained by the reduced risk of predation by small fish in more turbulent conditions, as well as by an initial entry into the flooded floodplain of larger individuals of fish for spawning, followed by the smaller ones for feeding.

EU Project of Life Programme “Algae Service for Life” Creates Tools for Ecological Service to Mitigate Cyanobacteria and Macroalgae Blooms in Freshwater Ecosystems

AbstractEU international project of LIFE programme “Algae Service for LIFE” seeks to promote best practices in ecological service and development of circular economy. The goal of the project is to demonstrate integrated efficient management of nutrients and nuisance algal blooms at the catchment scale by harvesting cyanobacteria scums and macroalgae mats in various types of water bodies (rivers, lakes and estuarine lagoon). Also, it seeks to raise awareness of the national and local authorities, business community and society on the environmental, water quality and health hazard issues. The paper provides the idea of applying ecological measures to control algal blooms. Thus, issues related to the causes and mechanisms of eutrophication in inland freshwaters as well as to consequences such as algal blooms are highlighted. The measures proposed in the project are briefly discussed in the light of European Union directives.

General characteristics of BOD kinetics in long-term experiments with water from Karelian waterbodies of various types

Long-term experiments (84–126 days long) on biochemical oxygen demand (BOD) were conducted to study the BOD kinetics in water samples from more than 30 waterbodies of the Karelian region and from the White Sea in different seasons of 2012–2017.The experiments were conducted under two incubation temperatures (10 and 20 °C or 2 and 10 °C) to estimate the temperature coefficient. Two approaches were applied to describe the BOD kinetics. The first one originated from a compilation of the data previously obtained for natural, contaminated and waste waters. The second one was based on visual classification involving BOD curves plotted for different waterbodies of Karelia. The distinctive feature of the long-term BOD test conducted here is that the BOD curve developed by the “apparent exponent” (APE) model during 30–80 days from the beginning of the experiments in some studied cases. This situation is completely different from the classical case, where autochthonous organic matter oxidation follows the exponential model in the first 15–20 days. BOD curve kinetic parameters were compared for еру APE and exponential models. The origins of APE curve formation were identified and described. The suspension of BOD development under various temperature conditions was explained. In the future, long-term BOD tests can be applied for water quality assessment together with the characteristics of organic matter content.

Evaluation of Water Indices for Surface Water Extraction in a Landsat 8 Scene of Nepal.

Accurate and frequent updates of surface water have been made possible by remote sensing technology. Index methods are mostly used for surface water estimation which separates the water from the background based on a threshold value. Generally, the threshold is a fixed value, but can be challenging in the case of environmental noise, such as shadow, forest, built-up areas, snow, and clouds. One such challenging scene can be found in Nepal where no such evaluation has been done. Taking that in consideration, this study evaluates the performance of the most widely used water indices: Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Modified NDWI (MNDWI), and Automated Water Extraction Index (AWEI) in a Landsat 8 scene of Nepal. The scene, ranging from 60 m to 8848 m, contains various types of water bodies found in Nepal with different forms of environmental noise. The evaluation was conducted based on measures from a confusion matrix derived using validation points. Comparing visually and quantitatively, not a single method was able to extract surface water in the entire scene with better accuracy. Upon selecting optimum thresholds, the overall accuracy (OA) and kappa coefficient (kappa) was improved, but not satisfactory. NDVI and NDWI showed better results for only pure water pixels, whereas MNDWI and AWEI were unable to reject snow cover and shadows. Combining NDVI with NDWI and AWEI with shadow improved the accuracy but inherited the NDWI and AWEI characteristics. Segmenting the test scene with elevations above and below 665 m, and using NDVI and NDWI for detecting water, resulted in an OA of 0.9638 and kappa of 0.8979. The accuracy can be further improved with a smaller interval of categorical characteristics in one or multiple scenes.