Lotic Research Articles

Presence of microplastics during high rainfall events in the Cauvery River (South India): Ecological risk and cultural practices.

Rivers directly support the development of a region/country; however, globally, these aquatic regions are impacted by recent human activity. During a rainfall event, we monitored the baseline information on the spatial variability of microplastics (MPs) in the Cauvery River in South India. Forty surface water samples from two selected sites were collected between 27 September and 16 October 2022 during the commencement of monsoon which indicates 69 and 43 pieces L-1 of MPs, respectively. SEM and FTIR analysis on the surface morphotypes (cracks, grooves, pits) and elemental (Si, Ti, Mg, Cu, Ta) presence/adsorption of these elements' (in particle) surface indicates surface deformation of fibers, which is mainly due to external input/forces. Fragments of polymers establish a high degree of deterioration indicating its longer trajectory in the aquatic environment. The origin of extended fiber ranges between 631.65 and 5639.9µm, which is being associated with laundry activities for textiles, household items, and fishing gear. Toxicity and ecological risk assessment suggest significant degree of weathered MPs due to photo-oxidation process and aging owing to exposition of intense UV light. This research serves as a strong illustration of the multiple pressures from urban development and cultural practices that have a bigger influence on the river ecosystem like Cauvery River and regular monitoring.

Assessing the Water Quality and Its Influence on the Chlorophyll-a Concentration in the Karnaphuli River Estuary

The Karnaphuli river, essential for the economy and biodiversity of Bangladesh, faces increasing threat due to the proximity of industries, necessitating regular water quality monitoring to safeguard both environmental and economic interests. Hence, this study investigates the nutrient distribution and physicochemical parameters (pH, temperature, turbidity, dissolved oxygen, and electric conductivity) in relation to the chlorophyll a dynamics in the Karnaphuli river estuary during the monsoon season for evaluating water quality in the river estuary, stretching about 42 kilometres. Surface and deep-water samples have been collected from five different stations. Nutrients, chlorophyll concentration, and dissolved oxygen have been evaluated using a Continuous Flow Autoanalyzer, spectrophotometer, and DO kit, respectively, while electric conductivity, temperature, turbidity, and pH have been measured using a CTD tool. Spatial mapping and correlation analysis have been conducted as well. Temperature and pH values didn’t show much fluctuation within the sampling stations falling within the range of 29°C-31°C and 6.5-7.5, respectively. Positive correlation of pH with ammonia at surface water (r=92) indicates that the effluents of ammonia plants are the primary source of pH in river water. TSP plant effluent has been shown to cause turbidity, evident from the positive correlation between phosphate and turbidity both at surface and deep water (r=91). Increase in turbidity (562.1 NTU) resulted in a decrease in dissolved oxygen (3 mg/L), which poses a serious threat to the survival of aquatic life, including fish, in the river downstream. Decreased water quality at river downstream is evident by comparatively low chlorophyll presence of 1.5 μg/L. However, the shallow coastal region in the study area is indicative of a healthy aquatic ecosystem evident by the presence of high productivity indicated by high chlorophyll concentration of 8.9 μg/L, which is due to comparatively low levels of turbidity and also the water condition there met the standard DO for fisheries (>5mg/L). The findings underscore the critical importance of regular water quality monitoring in the Karnaphuli river to safeguard both the environment and economy of Bangladesh, urging collective action to mitigate the escalating threats posed by industrial activities and ensure the long-term sustainability of the river ecosystem. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 13(1), 2024, P 91-104

Remote Sensing Estimation of CDOM for Songhua River of China: Distributions and Implications

Rivers are crucial pathways for transporting organic carbon from land to ocean, playing a vital role in the global carbon cycle. Dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) are major components of dissolved organic matter and have significant impacts on maintaining the stability of river ecosystems and driving the global carbon cycle. In this study, the in situ samples of aCDOM(355) and DOC collected along the main stream of the Songhua River were matched with Sentinel-2 imagery. Multiple linear regression and five machine learning models were used to analyze the data. Among these models, XGBoost demonstrated a superior, highly stable performance on the validation set (R2 = 0.85, RMSE = 0.71 m−1). The multiple linear regression results revealed a strong correlation between CDOM and DOC (R2 = 0.73), indicating that CDOM can be used to indirectly estimate DOC concentrations. Significant seasonal variations in the CDOM distribution in the Songhua River were observed: aCDOM(355) in spring (6.23 m−1) was higher than that in summer (5.3 m−1) and autumn (4.74 m−1). The aCDOM(355) values in major urban areas along the Songhua River were generally higher than those in non-urban areas. Using the predicted DOC values and annual flow data at the sites, the annual DOC flux in Harbin was calculated to be approximately 0.2275 Tg C/Yr. Additionally, the spatial variation in annual CDOM was influenced by both natural changes in the watershed and human activities. These findings are pivotal for a deeper understanding of the role of river systems in the global carbon cycle.

Change in Water Quality of the Vistula River During the Emergency Discharge of Untreated Wastewater

This paper presents an environmental analysis of the impact of an emergency discharge of untreated municipal sewage from the sewage system in Warsaw. This study was based on monitoring water quality in the Vistula River at stations located before and after the discharge site. Statistical analysis, including correlation analysis and Friedmann’s test, was performed for the data covering eight measurement stations and sixteen chemical parameters. The results confirm the negative impact on the water quality in the river, especially in the mixing zone. In the mixing zone, a statistically significant increase in pollution was found for TN, N-NO3−, N-NH4+, TP, P-PO43+, SS, EC, COD, and TOC. The results of the analysis show the self-cleaning capacity of the river ecosystem and illustrate the response to a sudden, excessive influx of pollution. The direct impact of the untreated sewage discharge was found on a section of the river 1200 m after the place of the failure. The good ecological status and drinking water standards are not met in the mixing zone. The supply of water to the people requires the use of highly effective physical and chemical treatment.

Study on the Function and Planning of Urban River Ecological Corridor

This study investigates the functions and planning principles of urban river ecological corridors, highlighting their vital role in urban ecosystems. Urban rivers, which include both waterways and riparian zones, provide essential ecosystem services such as habitat provision, temperature regulation, pollutant filtration, and flood mitigation. However, rapid urbanization has led to the degradation of these corridors, resulting in habitat fragmentation, reduced biodiversity, and compromised ecological integrity. The paper reviews global efforts and strategies for urban river restoration, emphasizing the significance of ecological methods and public participation in the planning process. A case study of the Yuhangtang River in Hangzhou, China, exemplifies various restoration approaches, including traditional flood control, ecological restoration, and landscape design, all assessed using a multi-criteria decision-making (MCDM) framework. The findings indicate that employing the MCDM tool can facilitate planning that integrates the functions of river ecological corridors. Additionally, plans that achieve a balance of ecological, economic, social, and aesthetic benefits are more likely to gain public acceptance.

Study on the Function and Planning of Urban River Ecological Corridor

This study investigates the functions and planning principles of urban river ecological corridors, highlighting their vital role in urban ecosystems. Urban rivers, which include both waterways and riparian zones, provide essential ecosystem services such as habitat provision, temperature regulation, pollutant filtration, and flood mitigation. However, rapid urbanization has led to the degradation of these corridors, resulting in habitat fragmentation, reduced biodiversity, and compromised ecological integrity. The paper reviews global efforts and strategies for urban river restoration, emphasizing the significance of ecological methods and public participation in the planning process. A case study of the Yuhangtang River in Hangzhou, China, exemplifies various restoration approaches, including traditional flood control, ecological restoration, and landscape design, all assessed using a multi-criteria decision-making (MCDM) framework. The findings indicate that employing the MCDM tool can facilitate planning that integrates the functions of river ecological corridors. Additionally, plans that achieve a balance of ecological, economic, social, and aesthetic benefits are more likely to gain public acceptance.

Quantitative study on the relationship between land use and land cover and diatom community in urban streams.

The study of the impact of urbanization on river ecosystems is an important part of constructing sustainable cities. How to quantitatively study the impact of urbanization on river ecosystems is the difficulty of urban ecological research. This study quantitatively investigated the effects of LULC on water quality and diatom assemblages in urban streams by correlation analysis, multivariate analysis, and path analysis. The results showed that (1) the percentage of LULC type in buffer 600m of reference stream sites is significantly different from that of urban stream sites. In reference sites, the average percentage of green was 94.2%, barren 3.3%, and impervious surface 2.5%. In urban upstream sites, the average percentage of impervious surface was 63.1%, green 32.8%, water 3.3%, and barren 0.8%. In urban downstream, the average percentage of impervious surface was 59.0%, green 36.5%, water 2.7%, and barren 1.8%. (2) One-way analysis results showed that water quality variables were significantly differences among the sites. The correlation analysis results indicated that LULC had a significant influence on water quality. Green had a significant negative correlation with high concentrations of NO3-N, NH4-N, and Cond. but positively correlated with MSUBST. RDA results showed that the selected water quality variables, MSUBST, and LULC types have a significant impact on the spatial patterns of the diatom assemblages. (3) Path analysis results showed that both LULC types and water quality variables exerted significant effects on diatom assemblages. This study first clarifies the quantitative relationships among LULC types, water quality, and diatom assemblages in the Beijing area. And green land was positively correlated with water quality and river ecosystems. We believed that increasing green space in urban core areas is an effective measure for improving water quality and restoring river ecosystems in the urban area.

Properties of Biofilm Prokaryotic and Eukaryotic Communities in a Representative Hypereutrophic Urban River

ABSTRACT Biofilms play an important role in nutrient and food web dynamics of shallow aquatic ecosystems. Multiple prokaryotic and eukaryotic microorganisms within biofilms interact with each other to shape the community structure and their functional attributes. However, there is no clear understanding of varied patterns of biofilm prokaryotic versus eukaryotic microbial abundances, diversities and communities, which limit our understanding of how biofilm communities and functions in hypereutrophic urban river ecosystems are changing. To elucidate the properties of biofilm communities and controls on biofilm communities in a hypereutrophic urban river, we conducted a one‐year study to investigate the seasonal and water‐depth variations on the abundance/biomass, diversity and structure of biofilm prokaryotic and eukaryotic communities. The structure and dynamics of biofilm prokaryotic and eukaryotic communities were determined by high‐throughput sequencing based on the 16S and 18S rRNA gene. Sequencing revealed that Proteobacteria, Bacteroidota and Cyanobacteria were the three dominant phyla in biofilm prokaryotic communities, and Rotifera, Chlorophyta, Annelida and Bacillariophyta were the four dominant phyla in biofilm eukaryotic communities. Biofilm bacterial abundance depended mainly on the water temperature, whereas biofilm algal biomass correlated with rotifer grazing and light levels. Prokaryotic communities had higher species richness and diversity than eukaryotic communities. Species richness and diversity displayed significant seasonal variations with minima for prokaryotic communities in winter and eukaryotic communities in summer, which were linked to water temperature and rotifer grazing, respectively. Variations in biofilm prokaryotic and eukaryotic community composition were mainly related to ammonia concentration and water temperature, respectively. The co‐occurrence network analysis suggested that rotifer grazing could considerably decrease the complexity of the biofilm network in summer, and the algal groups, especially for Chlorophyta and Bacillariophyta, were the key to the formation of stable biofilm networks. There were significant differences in seasonal and water‐depth heterogeneity of biofilm prokaryotic and eukaryotic community composition. Our findings indicate that variations in water temperature, light level, rotifer grazing and nutrients (especially ammonia) appreciably contribute to changes in the abundance, diversity and composition of biofilm prokaryotic versus eukaryotic communities in the hypereutrophic urban river. These findings increase our understanding of biofilm community characteristics in hypereutrophic urban rivers and provide insights for water pollution remediation strategies.

The influence of water conservancy project on microplastics distribution in river ecosystem: A case study of Lhasa River Basin in Qinghai-Tibet Plateau

Water conservancy projects affect the migration, suspension, and deposition of microplastic (MP). However, its impact on MP pollution of river ecosystem remains elusive. Herein, we investigated the MP characteristics and the influence of water conservancy projects on MPs in the Lhasa River Basin of the Qinghai-Tibet Plateau, China. The results demonstrated that the MPs concentration in surface water decreased from upstream to downstream, as more MPs in surface water were settling down and stored in reservoir sediments in the midstream. It is postulated that reservoir sedimentation of MPs occurs at a greater rate due to the barrier effect of reservoirs, steady hydrodynamics, and weak salinity-induced buoyancy. To evaluate the ecological risk of the Lhasa River Basin, the pollution load index, the polymer hazard index, and the potential ecological risk index were analyzed. The upstream exhibits elevated polymer hazard index values (>100), and the potential ecological risk index values in the Lhasa River Basin showed ecological risk similar to those of pollution load index values. This research represents the initial exploration of MP distribution within the entire Lhasa River basin, providing a foundational framework for investigating the impact of water conservancy projects on MP migration.

Assessment of Water Poverty Index (WPI) Under Changing Land Use/Land Cover in a Riverine Ecosystem of Central India

Watershed Development is a very common phenomenon in the river basins in India due to its dynamic and continuously changing nature, which are interconnected via. Land use/land cover (LULC) change and water poverty scenario over time. In the present study, the samples were chosen from seven sampled villages for the Water Poverty Index (WPI) in the upper Tons River Basin. Among them, Ghunwara and Maihar Village exhibit the highest and lowest WPI, i.e., 98.1 and 62.91 out of 100, respectively. This indicates that villages with a high WPI face challenges in their water requirements, regardless of the seasonal river serving the basin area. Conversely, villages with a low WPI can satisfy their water needs solely from the basin. The present analysis of the Upper Tons River Basin suggests that Land Use and Land Cover (LULC) will undergo influences or adjustments at various stages, ultimately affecting agricultural land in the impact region. It also becomes evident that areas with limited land use and land cover (LULC) extensions exhibit lower Water Productivity Index (WPI), primarily due to their reliance on agricultural land. It is observed that alterations, reductions, or modifications in LULC lead to changes in multiple aspects of agricultural land, resulting in noticeable variations in various metrics. The present paper not only evaluates the land use in the Upper Tons River Basin spanning from 2001 to 2021 but also highlights the changing patterns that impact water resources and their utilization capacity. Furthermore, the study estimates the influence of reducing specific features on the distribution of WPI and other LULC parameters. The Upper Tons River Basin faces challenges such as unfavorable rainfall patterns and inadequate planning for irrigation at the fundamental and local levels. Additionally, its geographical location in a rainfed area negatively affects the WPI.

Effects of Channelization on Macroinvertebrate Assemblages in a Small Stream: The Case of Awetu in Jimma City, Ethiopia

Freshwater ecosystems are increasingly modified worldwide by anthropogenic activities. Land use change is one of the leading factors responsible for stream ecosystem degradation. Physical habitat disturbance due to channelization is among the factors responsible for the loss of biodiversity and degradation of river water quality worldwide. Since 2020, Jimma City municipality has been beautifying the city and one of the activities is channelizing using concrete embankment, a part of the Awetu stream that runs through the city. The main aim of this study is to assess the effect of channelization on macroinvertebrate assemblages and the water quality of the Awetu stream. A cross-sectional study was conducted in April 2022. Macroinvertebrates, water samples, and habitat data were collected from 21 sampling sites along the three segments of the stream (upstream, channelized, and downstream). Data were analyzed for different macroinvertebrate metrics and water quality parameters. Canonical Correspondence Analysis was used to examine the overall relationship between macroinvertebrate assemblages and water quality parameters. The upstream site has better macroinvertebrate assemblages than channelized and downstream sites (p<0.05). The downstream site showed better assemblage compared to the channelized site, though it was not significant. Regarding water quality parameters, a significant variation was observed between channelized and, un-channelized sites (upstream and downstream) (p<0.05). The habitat condition score varied from 47 (poor) at channelization to 150 (suboptimal) upstream. Upstream sites were found to have relatively better macroinvertebrate assemblages, better water quality, and good habitat conditions. The downstream sites had lower macroinvertebrate assemblages, poor habitat conditions, and degraded water quality compared to the upstream sites. The channelized segment had the poorest habitat, with poor macroinvertebrate assemblages and water quality. Thus, the conservation of habitat conditions along the channelized segments of the Awetu stream is recommended to improve the water quality and macroinvertebrate assemblage.

A Spatial Model of Microplastic Pollution Mitigation as an Effort to Preserve the Brantas River Ecosystem

A Spatial Model of Microplastic Pollution Mitigation as an Effort to Preserve the Brantas River Ecosystem

Assessment of River Ecological Health Status and Interbasin Water Transfer Potential: Case study of Luapula River Basin in Zambia

Water transfer is one mechanism for meeting increasing water demand in water-stressed areas. However, moving water from one area to another often disturbs the ecosystem including the fisheries biodiversity and growth patterns. Thus, when contemplating water transfer, baseline information on the status of the fisheries biodiversity and condition is cardinal for sustainable fisheries management during and after water transfer implementation. This work aimed at investigating the current fisheries condition (biodiversity, weight length relationship and condition factor) of the Luapula River Basin (LRB) to explore potential and implications for future interbasin water transfer on the basin fisheries. The fishes were sampled during the 2022/2023 dry and wet season at selected sites in LRB. Biodiversity indices, fish weight/length relationship and condition factor were used to describe the fish biodiversity, growth patterns and wellbeing which described the status of the aquatic condition of the donor basin. Species Richness, Shannon Diversity Index, Simpson Index and Evenness ranged between 0.8902 to 1.664, 0.9167 to 2.1437, 0.4416 to 0.8683 and 0.4172 to 0.8940 respectively. The growth coefficient (b) ranged from 1.223 to 3.755 indicating negative and positive allometric growth. The condition factor ranged between 0.692 and 2.218. Thus, it can be said that the LRB has good fish biodiversity albeit with some species showing dominance, normal growth pattern and wellbeing showing bias towards undisturbed habitats and physiological state. As such, this status quo of LRB needs to be maintained prior to, during and after IBWT implementation.

Taxonomic composition of phytoplankton in various continental aquatic hydroecosystems of Ukraine

The paper deals with present-day taxonomic composition of phytoplankton in various continental aquatic ecosystems of Ukraine (Kaniv Reservoir, the Western Bug River (with tributaries), Prypiat River (with tributaries), Sula River (within Nyzhniosulskyi National Natural Park, ponds (Hostomel town), large lakes of the Danube River) according to the modern algological nomenclature AlgaeBase. Within 2000–2022 in the phytoplankton of aquatic ecosystems under study 455 species of algae were identified, represented by 467 infraspecies taxa from 206 genera, 102 families, 53 orders, 18 classes and 8 phyla. The most diverse were Bacillariophyta (25–50%), Chlorophyta (22–39%) and Cyanobacteria (7–16% of floristic spectrum). Phytoplankton responds to present climate change by increase in Cyanobacteria share. The taxonomic hierarchy of algae, identified in plankton, is characterized by the following regression: Bacillariophyta &gt; Chlorophyta &gt; Cyanobacteria &gt; Ochrophyta &gt; Euglenozoa. Analysis of the taxonomic composition of Bacillariophyta at different levels of their systematic hierarchy (families, genera — according to Kendall index; species (infraspecie taxa) — according to Sørensen index) has made it possible to reveal the following patterns. The Kendall index for leading families varied within 0.31–0.72. The highest level of similarity was observed for lotic ecosystems. The Kendall index for leading genera varied between 0.11 and 0.59. The highest similarity level was observed between ecosystems of one type, for example, lotic (the Prypiat River and the Western Bug River) or lentic (ponds of Hostomel town and large Danube lakes). Cluster analysis of species similarity according to Sørensen index shows that two clusters can be distinguished in the dendrogram: lotic ecosystems and lentic ecosystems. The long-term data on the taxonomic composition of phytoplankton (algae present in water column at the moment of sampling) give evidence of high diversity thereof in various aquatic ecosystems of Ukraine.

The ADDRESS of a grain: Sediment particle tracking as an approach to assessing ecosystem quality in dammed reservoirs

The study integrates hydrodynamic modelling and geospatial analysis methods to describe the dynamic transport and sedimentation conditions of suspended solids (SS) in large lowland reservoirs. The method was tested on a dam reservoir on the Vistula River (Poland). Stochastic particle tracking was used with a Lagrangian approach, then geostatistical analyses to interpret the simulation results.It is shown that, excluding the backwater, SS sedimentation is greatest in distal parts of the reservoir's lacustrine and river sections. The reservoir retains an average of 79 % of inflowing SS. The primary process affecting the sedimentation of SS is a dam-wards increasing fineness of settling grains. Hydrodynamic simulation results showed deposition of clay fraction to also be possible in the reservoir's upper part, even during floods. Moreover, sand grains entered the dam even during very low flows. Interpretation of Particle Tracking Model (PTM) simulation results and geostatistical modelling reveals that the submerged bed of the pre-dam river still has a transport function, while fine SS accumulates in slow-flowing areas outside it. The anastomosing pre-dam riverbed still influences flow conditions and SS deposition in the upper and middle reservoir. PTM modelling and geostatistical analyses determined the influence of hydrodynamic conditions on the spatial variability of SS sedimentation in terms of the quantity and grain-size distribution of sedimenting matter.An original indicator (ADDRESS [A]; Accumulation or Discharge of Dam REservoir Suspended Solids) was developed determining the ability of polymictic reservoirs to either retain SS of different diameters or allow them through the reservoir to be discharged through the dam. The indicator quickly and simply determines particle behaviour under given hydrological conditions. Information on whether all or only some of grains of specific diameters will flow through the dam is important for explaining many natural processes affecting the reservoir ecosystem and the river ecosystem below the dam.

A framework for implementation of environmental flow requirements through community perceptions – the case of Bargi Dam, Jabalpur District, Madhya Pradesh

A framework for implementation of environmental flow requirements through community perceptions – the case of Bargi Dam, Jabalpur District, Madhya Pradesh

Impact of discharge regulation on zooplankton communities regarding indicator species and their thresholds in the cascade weirs of the Yeongsan River

Discharge regulation in rivers with cascade weirs profoundly alters natural flow dynamics, impacting habitat characteristics and leading to the homogenization of community structure and function. Identifying indicator species and their ecological thresholds is crucial for effectively monitoring and assessing the ecological conditions of regulated river systems. It is also essential for guiding conservation and management efforts. In this study, we investigated the influence of discharge patterns on zooplankton communities in the Yeongsan River, specifically focusing on the effects of flow regulation by cascade weirs. We analyzed the zooplankton community dynamics over a 12-year monitoring period and demonstrated the significance of discharge in shaping river ecosystem dynamics. Species indicator tests and gradient forest modeling were used to identify indicative genera and establish their ecological thresholds under various discharge patterns. Our findings revealed a distinct and significant discharge effect on zooplankton community composition and diversity, independent of water quality and nutrient-related factors. Monsoonal rainfall influenced the discharge patterns, which were categorized into three levels; this classification was further supported by indicator species and their responses. Despite their low abundances limiting clear responses, indicator genera, such as Rotaria and Macrothrix, were shaped by discharge levels. This study highlighted the need to incorporate discharge considerations into river management and conservation strategies to safeguard aquatic biodiversity. Our study provides valuable insights into sustainable river ecosystem management by elucidating the ecological consequences of flow regulation by cascade weirs.

A fish community comparison upstream and downstream a high-head dam on the Upper Mississippi River

Abstract Standardized sampling is useful for detecting and monitoring variations in fish communities and the establishment and spread of invasive species. Lock and Dam 19, a high-head dam with a 10- meter hydraulic head, creates the largest impoundment on the Upper Mississippi River. Upstream, Pool 19 is characterized by static water levels and expansive macrophyte beds. Downstream, Pool 20 is characterized by lotic conditions and sparse vegetation. Lock and Dam 19 serves as barrier to upstream migration of fishes, particularly Bigheaded carp (Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molotrix). There is limited standardized fisheries data available for Pools 19 and 20, particularly in off-channel areas. In 2013 and 2014, we conducted two years of standardized electrofishing in Pools 19 and 20 to 1) detect a presence of adult or juvenile Bigheaded carp, 2) quantify differences in fish community structure (i.e., relative abundance of species) between Pools 19 and 20 and among strata (i.e., backwater, side channel, main channel, and impounded reaches), and 3) quantify hydrological differences (i.e., water quality variables) between Pools 19 and 20 and among strata. We detected two Bigheaded carp upstream Lock and Dam 19, the first to be documented using a standardized collection method. We used permutational multivariate analysis of variance using distance matrices (veganR package version 2.6-4) to determine that fish community structure differed significantly between pools (P&amp;lt; 0.01) and among strata (P&amp;lt; 0.01), except between main and side channel borders. We determined water quality variables differed significantly between the pools and among strata demonstrating strata proportional differences may drive the fish community differences between Pools 19 and 20. We have demonstrated that expanding standardized sampling efforts to Pools 19 and 20 is important to understand long-term changes in fish assemblages and the effects of Lock and Dam 19 on the ecology of the Upper Mississippi River.

Anthropogenic activities disturb phytoplankton taxa and functional groups in an urban river

Anthropogenic activities have substantial impacts on river ecosystems, yet how phytoplankton taxa and functional groups respond to varying levels of anthropogenic activity in urban rivers remains poorly understood. Herein, we investigated the sensitivity of phytoplankton taxa and functional groups to anthropogenic disturbances in the Bahe River, which experiences increased anthropogenic activity intensity from upstream to downstream. We found that both phytoplankton composition and niche breadth exhibited distinct variations among the three reaches with different anthropogenic disturbances. Notably, we observed a marked increase in the abundance of potential bloom-forming species in the river section with the highest anthropogenic disturbance, suggesting that anthropogenic activities might promote the growth and proliferation of these species. Compared to geographical and physiochemical factors, anthropogenic activities were identified as the primary driver of changes in phytoplankton taxa and functional groups. Increasing levels of anthropogenic activities potentially led to higher concentrations of ammonium nitrogen and total phosphorus, further influencing niche differentiation among phytoplankton taxa and functional groups. Our study offers profound insights into the impacts of anthropogenic disturbances on phytoplankton, emphasizing the necessity of integrating watershed-scale human activity management into strategies for controlling phytoplankton in urban rivers.

Metagenomic insights into microbial community, functional annotation, and antibiotic resistance genes in Himalayan Brahmaputra River sediment, India.

The Brahmaputra, a major transboundary river of the Himalayas flowing predominantly through Northeast India, particularly Assam, is increasingly endangered by contamination due to rapid urbanization and anthropogenic pressures. These environmental changes pose significant risks at the microbial level, affecting nutrient cycling and productivity, and thereby impacting river ecosystem health. The next-generation sequencing technology using a metagenomics approach has revolutionized our understanding of the microbiome and its critical role in various aquatic environments. The present study aimed to investigate the structure of the bacterial community and its functional potentials within the sediments of the Brahmaputra River, India, using high-throughput shotgun metagenomics. Additionally, this study sought to explore the presence of antimicrobial resistance genes in the river's sediment. Shotgun metagenomics revealed a diverse bacterial community comprising 31 phyla, 52 classes, 291 families, 1,016 genera, and 3,630 species. Dominant phyla included Pseudomonadota (62.47-83.48%), Actinobacteria (11.10-24.89%), Bacteroidetes (0.97-3.82%), Firmicutes (0.54-3.94%), Cyanobacteria (0.14-1.70%), and Planctomycetes (0.30-0.78%). Functional profiling highlighted significant involvement in energy metabolism, amino acid and central carbon metabolism, stress response, and degradation pathways, emphasizing the microbial community's role in ecosystem functioning and resilience. Notably, 50 types of antibiotic resistance genes (ARGs) were detected, with resistance profiles spanning multidrug, aminoglycoside, β-lactam, fluoroquinolone, rifampicin, sulfonamide, and tetracycline classes. Network analysis underscored the intricate relationships among ARG subtypes, suggesting potential mechanisms of resistance propagation. Furthermore, plasmid-related genes and 185 virulence factor genes (VFGs) were identified, indicating additional layers of microbial adaptation and potential pathogenicity within the river sediments. This comprehensive microbial and functional profiling of the Brahmaputra's sediment metagenome provides crucial insights into microbial diversity, resistance potential, and ecological functions, offering a foundation for informed management and mitigation strategies to preserve river health and mitigate pollution impacts.