Freshwater Ecosystems Research Articles

Difference in Community Structure and Function of Bacteria Attached to Stems and Leaves of Potamogeton crispus Compared to that of Bacteria in the Overlying Water and Sediment

The stems and leaves of submerged macrophytes usually grow below the water surface and could provide a good biological carrier for the colonization and growth of planktonic bacteria in water. Therefore, attached bacteria on the stem and leaf surfaces of submerged macrophytes are important components and play a crucial role in aquatic ecosystems. To further understand the structure characteristics and functional differences of the bacterial community attached to the stems and leaves of submerged macrophytes, the submerged macrophytes Potamogeton crispus and the overlying water and sediment were sampled and analyzed in this study. The results showed that a total of 10 320 OTUs were detected in the P. crispus samples, the overlying water samples, and the sediment samples. These OTUs included 64 phyla, 189 classes, 448 orders, 721 families, and 1 366 genera. The richness and diversity of bacterial communities in sediments were the highest, followed by the stem and leaves of P. crispus, and the alpha diversity index of planktonic bacteria in water was the lowest. Significant differences （P<0.05） were observed among the four alpha diversity indices of the three source samples. Bacterial communities with greater similarity were obtained from the same source samples, but there was more distinct community composition dissimilarity in bacteria collected from the submerged macrophytes and the overlying water and sediment samples （P<0.05）. At the level of phylum, order, and genus classification, the relative abundance of most dominant bacterial species, non-dominant species, and occasional species showed significant differences among the three source samples （P<0.05）. Proteobacteria, Actinobacteria, and Bacteroidetes were common dominant bacterial phyla for the three source samples, while Firmicutes were unique dominant phyla for attachment bacteria on the plant stem and leaves of P. crispus. There were differences in carbohydrate metabolism, energy metabolism, amino acid metabolism, cofactors, and vitamin metabolism among the three source samples （P<0.05）. The relative abundance of chemical heterotrophic and oxidative heterotrophic functional types in the stem and leaf samples of P. crispus was higher than that in the overlying water and sediment samples. In addition, higher nitrate reduction, nitrogen respiration, and nitric acid respiration functions were observed in sediment samples. To summarize, the stems and leaves have the potential to encourage bacterial colonization and create a unique bacterial community on the surface of submerged macrophytes. Submerged P. crispus macrophytes and their surroundings （water and sediment） play different roles in the biogeochemical cycling of nutrients in the freshwater ecosystem.

Abundance of fecal indicator bacteria and diversity of Escherichia coli associated with poultry farms and pasture land cover in streams of northwestern South Carolina

Livestock can contribute fecal indicator bacteria (FIB) to waterbodies. However, few studies have examined the relationship between watershed land use or land cover involving livestock production and the genetic diversity of Escherichia coli in freshwater ecosystems. Our major goal was to determine if FIB abundance and E. coli phylogenetic group distributions in headwater streams are related to livestock production in rural watersheds in South Carolina. In both 2017 and 2018, grab samples were collected from streams at summer baseflow. In 2017, we collected samples from watersheds with or without poultry rearing facilities (PRFs). In 2018, we collected samples from streams draining watersheds with mixed forest and pasture cover and from streams in mostly forested watersheds. In both summers, we measured concentrations of total coliforms, E. coli, and Enterococcus. We also categorized E. coli isolates into one of four phylogenetic groups (A, B1, B2, D). Streams with PRFs in their watersheds had significantly higher concentrations of Enterococcus but not total coliforms or E. coli than streams in watersheds without PRFs. Also, B2 isolates were less frequent and B1 isolates were more frequent in watersheds with PRFs than in those without. Streams draining mixed forest/pasture watersheds had significantly higher concentrations of total coliforms and E. coli but not Enterococcus, as well as higher frequencies of B1 isolates, than streams in mostly forested watersheds. Overall, the most frequent E. coli phylogenetic groups in watersheds with animal production appeared consistent with the phylogenetic groups that are especially abundant in poultry or mammalian livestock feces.

Wetland Species Mapping Using Advanced Technological Measurement

ABSTRACTWetlands are pivotal in supporting the natural ecosystem and maintaining biodiversity while being susceptible to anthropogenic activities and climate change. However, monitoring wetlands over a large geographical and temporal extent is challenging. Vegetation health can be considered a good indicator of wetland conditions, and measuring chlorophyll content will provide insight into vegetation health. Linking wetland species mapping from chlorophyll spectral indices to local and regional conservation strategies could improve biodiversity conservation. Here, we apply this to Keetham Lake, India, using machine learning methods (relevance vector model) and hyperspectral measurements. From 10 chlorophyll‐sensitive spectral indices, we identified four as best performing, particularly for: TVI + CCCI + NDRE for calibration and NDRE + TVI for validation data. The least performing combinations were MCARI for calibration and TVI + CCCI + NDRE + MCARI for validation. Overall, we identified that NDRE + TVI was the best‐performing pair of spectral indices for chlorophyll assessment and implementation in wetland species. This approach allows for precise mapping of wetland species, providing data on their extent and the area they cover. By creating a digital database, this method enables long‐term monitoring of changes in wetland species' numbers and distribution, helping to assess trends of increase or decline in freshwater ecosystems. Such strategies are vital for supporting both local and global conservation efforts, offering insights for forward‐looking, data‐driven preservation initiatives.

Combined transcriptome and metabolome analysis reveals the mechanism of high nitrite tolerance in freshwater mussel Anodonta woodiana

Nitrite contamination and stress on aquatic organisms are increasingly emphasized in freshwater ecosystems. Freshwater bivalves exhibit high tolerance to nitrite; however, the underlying mechanism is unknown. Accordingly, this study investigated the tolerance mechanism of the globally occurring freshwater bivalve Anodonta woodiana. A. woodiana were exposed to nominal concentrations of 0, 250, 500, 1000, 2000, and 4000 mg/L nitrite for 96 h to calculate the 96-h median lethal concentration (96-h LC50). A combined transcriptome and metabolome analysis of the hemolymph (the most vital component of the bivalve immune system) was performed after exposing A. woodiana to 300 mg/L nitrite (approximately half the 96-h LC50) for 96 h. The 96-h LC50 of nitrite in A. woodiana was 618.7 mg/L. Transcriptome analysis identified 5600 differentially expressed genes (DEGs) primarily related to ribosomes, lysosomes, DNA replication, and nucleotide excision repair. Metabolome analysis identified 216 differentially expressed metabolites (DEMs) primarily involved in biosynthesis of amino acids, 2-oxocarboxylic acid metabolism, protein digestion and absorption, aminoacyl-tRNA biosynthesis, nucleotide metabolism, ABC transporters, and valine, leucine and isoleucine degradation. Combined transcriptome and metabolome analysis revealed that DEGs and DEMs were primarily associated with nucleotide (purine and pyrimidine) and amino acid metabolism (including aminoacyl-tRNA biosynthesis, cysteine and methionine metabolism, arginine and proline metabolism, and valine, leucine and isoleucine degradation) as well as the immune system (necroptosis and glutathione metabolism). This study is the first to describe the high tolerance of A. woodiana to nitrite and elucidate the molecular mechanisms underlying high nitrite tolerance in mussels.

Defensive responses of most antioxidant genes in the freshwater dinoflagellate Palatinus apiculatus to cadmium stress and their implications

Photosynthetic dinoflagellates are one of the major microalgal taxa, playing essential roles in biogeochemical cycles and food webs in aquatic environments. Some freshwater dinoflagellates are known to be sensitive to environmental conditions, like water quality and contaminants; however, their molecular toxicological responses are insufficiently discovered. In the present study, we evaluated the physiological and transcriptomic responses of the freshwater dinoflagellate Palatinus apiculatus exposed to cadmium (Cd), focusing on stress-responsive genes. The cell number of P. apiculatus decreased significantly at Cd concentrations above 0.25 mg/L after 72 h, with an estimated EC50 value of 1.35 mg/L. In addition, we constructed 87,207 transcriptomic contigs from the P. apiculatus cells exposed to the Cd. Differential expression gene analysis showed that 21.0 % of total contigs were statistically significant, including 8647 up-regulated and 4195 down-regulated genes. Gene Ontology enrichment results revealed that genes responsive to stress and external stimuli were highly expressed in Cd-treated cells. Moreover, Cd significantly induced reactive oxygen species (ROS) production in P. apiculatus cells, and their patterns were similar to the expressions of certain antioxidant genes. Among the selected genes, GR expression levels were down-regulated, which may lead to the failure of cell defense against heavy metals. These results showed molecular defense pathways of the freshwater dinoflagellate P. apiculatus against the heavy metal that could be served as potential sensitive biomarkers for evaluating molecular toxicity in freshwater ecosystems.

Bioprospecting of Metabolites from Actinomycetes and their Applications.

Actinomycetes are present in various terrestrial and aquatic habitats, predominantly in the soil rhizosphere, encompassing marine and freshwater ecosystems. These microorganisms exhibit characteristics that resemble both bacteria and fungi. Numerous actinomycetes exhibit a mycelial existence and undergo significant morphological transformations. These bacteria are widely recognized as biotechnologically significant microorganisms utilized for the production of secondary metabolites. In all, over 45% of all bioactive microbial metabolites are produced by actinomycetes, which are responsible for producing around 10,000 of them. The majority of actinomycetes exhibit substantial saprophytic characteristics in their natural environment, enabling them to effectively decompose a diverse range of plant and animal waste materials during the process of decomposition. Additionally, these organisms possess a sophisticated secondary metabolic system, which enables them to synthesize almost two-thirds of all naturally occurring antibiotics. Moreover, they can create a diverse array of chemical compounds with medical or agricultural applications, including anticancer, antiparasitic, and antibacterial agents. This review aims to provide an overview of the prominent biotechnological domains in which actinobacteria and their metabolites demonstrate noteworthy applicability. The graphical abstract provides a preview of the primary sections covered in this review. This paper presents a comprehensive examination of the biotechnological applications and metabolites of actinobacteria, highlighting their potential for patent innovations.

Genetic transformation of the freshwater diatom Cyclotella meneghiniana via bacterial conjugation

Diatoms, the most species-rich algae, produce the main primary productivity of marine and freshwater ecosystems. Though, genetic transformation has been established in a variety of marine diatoms, genetic modification of freshwater diatoms is still difficult to achieve. Centric diatom Cyclotella is a major genus of freshwater diatoms, and C. meneghiniana is the most well-known and intensively studied species in this genus. In this study, episomal plasmids for C. meneghiniana were constructed, and endogenous promoters of fucoxanthin chlorophyll a/c-binding protein 3 gene (Fcp3) or ribosomal protein L14 gene (RL14) were used to drive the expression of blasticidin-S deaminase gene (bsr), enhanced green fluorescent protein gene (eGFP) and β-glucuronidase gene (GUS). The plasmids were introduced into algal cells by bacterial conjugation, and transformants were obtained by screening on solid plates containing 0.2 μg mL−1 blasticidin-S with the transformation efficiency of 9–58 transformants per 106 cells. PCR analysis verified the transfer of the plasmid sequences in the cells, and the fluorescence detection and staining analysis demonstrated that eGFP and GUS proteins were expressed in the cytoplasm, indicating the successful and stable expression of exogenous genes in C. meneghiniana through bacterial conjugation.

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.

Dynamic models for estimating radiation doses to hydrobionts in a freshwater ecosystem

A model of radionuclide transfer in freshwater bodies, along with dosimetric models for estimating doses to aquatic biota species (including phytoplankton, zooplankton, zoobenthos, and fish), is presented. The results of the reconstruction of radiation doses to aquatic organisms living in the closed (non-flowing, lentic) Lake Uruskul, located in the vicinity of the Kyshtym accident, are provided. The contributions of the main dose-forming radionuclides, as well as both internal and external exposures, to the doses received by aquatic organisms over the 50 years following the Kyshtym accident are discussed. It is shown that benthic organisms received the highest doses (2.6-8.3Gy per day), while zooplankton experienced somewhat lower doses (up to 3.3Gy per day). Fish received doses of up to 4mGy per day during the first 100 days. Phytoplankton, with doses reaching up to 0.5Gy per day, occupied an intermediate position in this sequence. These doses could lead to long-term radiation effects.

Application of DNA metabarcoding in the dietary pattern of a nonbreeding white-tailed eagle population in Northeast Asia under supplementary feeding

Food supplementation has become an increasingly prevalent strategy for animal conservation. A large white-tailed eagle (Haliaeetus albicilla) population exists in a wetland in Northeast Asia during the boreal winter, mainly because of regular supplementary feeding. However, the use of supplementary food by eagles has not been assessed. In this study, we used non-invasive sampling and DNA metabarcoding to investigate the food composition of white-tailed eagles in a lake near a supplementary feeding site. Our results revealed that supplemental food was present in 94% of the samples, with a weighted percent of occurrence (wPOO) of 64.62%. In addition to supplementation, we identified 11 natural prey species, including fish, birds, and mammals, from freshwater, marine, and terrestrial ecosystems. After February, there was an increasing trend in the frequency of natural food items, especially of marine fish, in the diet of the eagles. Our study demonstrates the power of DNA metabarcoding in dietary studies of raptor species in the presence of supplementary feeding. Based on our results, multiple recommendations have been provided to achieve adaptive management of large nonbreeding populations of eagles in our study area.

Evaluating the role of recalcitrant dissolved organic matter in bacterial community dynamics in urbanized freshwater ecosystems

Dissolved organic matter (DOM) and recalcitrant dissolved organic matter (RDOM) play distinct roles in shaping microbial communities. However, characterizing these roles is difficult, especially in ecosystems subjected to varying degrees of anthropogenic influence. This study investigated the molecular compositions and ecological impacts of DOM and RDOM in the Fen River, Shanxi Taiyuan, comparing pristine upstream regions with highly urbanized downstream areas. Using 16S rRNA gene sequencing and LC-MS-based metabolomics, we observed significant shifts in microbial community composition, diversity, and metabolic functions. Upstream communities, characterized by higher diversity, were dominated by Bacteroidota, Proteobacteria, and Cyanobacteria, while downstream communities, influenced by pollution, exhibited increased expression of genes related to amino acid metabolism. Fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed that upstream DOM contained higher proportions of complex, high molecular weight compounds, including significant proportions of carboxyl-rich alicyclic molecules (CRAM) and island of stability (IOS) compounds, which play key roles in long-term carbon storage and microbial carbon sequestration. In contrast, downstream DOM was characterized as having lower aromaticity and more saturated compounds, with reduced proportions of CRAM and IOS, reflecting the impact of anthropogenic activities. These findings underscored the critical roles of CRAM and IOS in regulating DOM stability and microbial communities, further highlighting the need for targeted pollution control strategies to preserve ecosystem function in urbanized water bodies.

Coexistence in long-term managed lakes: Limited evidence of negative impacts of invasive macrophytes on fish communities

Invasive macrophytes are widespread and can disrupt freshwater ecosystems if not properly managed. Their impact on fish is a topic of ongoing discussion, with studies reporting contrasting results. Utilizing datasets spanning 17 years of monitoring across 34 lakes in Florida, we examined the effects of the primary non-native invaders water hyacinth (Eichhornia crassipes (Mart.) Solms), hydrilla ((Hydrilla verticillata L. f.) Royle), and water lettuce (Pistia stratiotes L.), plus the entire non-native macrophyte assemblage and abiotic variables on fish species richness, Shannon diversity, abundance, length, and biomass. Together, these indicators help assess and manage the impact of invasive species and environmental changes on freshwater ecosystems. Our study was conducted at both habitat and lake scales to ensure a more thorough understanding of potential impacts. We found evidence of a marginally positive influence of hydrilla on fish species richness and abundance, a positive influence of water lettuce on Shannon diversity, and a positive effect of water hyacinth on fish length, all at the habitat scale. Notably, these effects were largely analogous to those of native macrophytes. Water temperature of about 26 °C and dissolved oxygen levels between 5 and 10 mg/L appeared to be optimal for fish. Lakes located in northwest Florida exhibited higher fish diversity and abundance. The integrated use of ecological indicators reveals that long-term management of lakes might limit populations of non-native macrophytes, thereby reducing the adverse effects of invaders on fish communities and facilitating their coexistence. This study highlights the importance of management strategies and long-term monitoring in minimizing the impacts of invasive plants on freshwater ecosystems.

Differential regulation of magnesium transporters Slc41, Cnnm and Trpm6-7 in the kidney of salmonids may represent evolutionary adaptations to high salinity environments

Magnesium is important for enzymatic reactions and physiological functions, and its intracellular concentration is tightly regulated. Atlantic salmon has the ability to handle large changes in environmental Mg2+ concentration when migrating between freshwater and seawater habitats, making it a relevant model to investigate Mg2+ homeostasis. Parr-smolt transformation (PST) is a life history transition which prepares the freshwater juvenile for the marine environment. The kidney is one of the key organs involved in handling higher salt load in teleosts. Though several key Mg2+ transport families (SLC41, CNNM and TRPM6-7) have recently been identified in mammals and a few fishes, the molecular bases of Mg2+ homeostasis in salmon are not known. We found that all three families are represented in the salmon genome and exhibit a clear conservation of key functional domains and residues. Present study indicates a selective retention of paralogous Mg2+ transporters from the fourth whole genome duplication round (Ss4R) and a differential regulation of these genes, which suggests neo- and/or sub-functionalization events. slc41a1-1, cnnm4a1, -4a2 and trpm7-2 are the main upregulated genes in the kidney during PST and remain high or further increase after exposure to seawater (33 ppt). By contrast, slc41a1-2, -3a, cnnm3-1, and cnnm3-2 are only upregulated after seawater exposure. In addition, slc41a1-1, -2, and trpm7-2 respond when exposed to brackish water (12 ppt), while cnnm3-1 and cnnm3-2 do not, indicating the existence of a lower salinity threshold response for these members. Finally, the response of slc41a1-1, -2 and trpm7-2 in salmon was significantly reduced or completely abolished when exposed to Mg2+-reduced brackish water, while others were not, suggesting they might be specifically regulated by Mg2+. Our results are consistent with previous findings on other euryhaline teleosts and chondrichthyan species, suggesting the existence of common adaptive strategies to thrive in high salinity environments. Concomitantly, salmonid-specific innovations, such as differential regulation and recruitment of family members not previously shown to be regulated in the kidney (Cnnm1 and Cnnm4) of other vertebrates might point to adaptions associated with their very plastic anadromous life cycle.

Size Matters: The Effects of Polystyrene Nanoplastics on Parasite Transmission in the Daphnia‐Metschnikowia Host–Parasite System

ABSTRACT The accumulation of micro‐ and nanoplastics (MNPs) poses a significant threat to freshwater ecosystems. Nanoplastics (NPs; &lt; 1000 nm) are particularly concerning due to their ability to penetrate cellular membranes and disturb intracellular functions. While current research has predominantly focused on the toxicological impacts of MNP on individual species, their broader ecological effects, particularly on species interactions, remain poorly understood. Prior studies have indicated that smaller NPs within the nano‐size range generally cause more severe effects on individual organisms. However, the impact of varying NP sizes on species interactions has not been thoroughly explored. This study addresses this gap by examining the effects of polystyrene NP beads of two sizes (50 nm and 100 nm) and two concentrations (1 mg/L and 5 mg/L) on the infection dynamics of the fungal parasite Metschnikowia bicuspidata in two genotypes of the freshwater crustacean Daphnia magna. Our results indicated that lower NP concentrations (1 mg/L) had no significant effects on either host or parasite fitness. Exposure to 50 nm NPs at 5 mg/L significantly diminished both the parasite's transmission success and the host's lifespan. Conversely, 100 nm NPs at the same concentration enhanced parasite fitness. Given that M. bicuspidata is a widespread and virulent parasite affecting various Daphnia species globally, alterations in infection dynamics due to NP pollution could have broader implications for Daphnia populations and freshwater food webs. These findings highlight the critical need to incorporate species interactions into plastic pollution research and emphasise the importance of evaluating the effects of different NP sizes on ecological relationships to fully comprehend the ecological impact of MNP pollution.

Macroinvertebrates functional feeding groups (FFGs) of forested streams draining urban catchments in the Niger Delta: identifying and classifying vulnerable and tolerant FFGs

ABSTRACT This study aims to assess the vulnerability and tolerance levels of macroinvertebrate functional feeding groups (FFGs) in forested streams draining urban areas in the Niger Delta. It contributes to our understanding of how human activities affect freshwater ecosystems. Between 2008 and 2012, we conducted monthly measurements of physicochemical variables and collected macroinvertebrates. We categorised sampling sites into three groups based on disturbance levels: least impacted sites (LIS), moderately impacted sites (MIS), and heavily impacted sites (HIS). Multivariate (RLQ) analysis was used to visualise associations among physicochemical variables across the sampled sites, revealing distinct relationships between certain FFGs and different sites. The RLQ model we constructed showed that grazers and collector-filterers were predominantly observed in LIS, suggesting their vulnerability to environmental stressors. Conversely, predators and shredders were more prevalent in impacted sites (MIS and HIS), indicating their tolerance to disturbances such as elevated nitrate levels and higher water temperatures. The fourth corner graph highlighted differing responses of FFGs to physicochemical variables, with predators showing positive correlations with several factors but no significant association with phosphate levels. Overall, these findings showed the importance of considering the responses of different FFGs to environmental variables in assessing the health and integrity of aquatic ecosystems.

Emergence and persistence of Cyvirus cyprinidallo 2 (CyHV-2) in Prussian carp in Serbian lakes

Between 2018 and 2021, significant die-offs of Prussian carp (Carassius gibelio) occurred in five lakes in eastern, central and northern Serbia. In all cases, Cyvirus cyprinidallo 2, formerly named Cyprinid herpesvirus 2 (CyHV-2) infection was suspected, based on initial diagnostic observations. To determine the cause of these mass mortalities, real-time PCR assays targeting CyHV-2, CyHV-3, and SVCV were conducted. CyHV-2 DNA was detected in the affected populations, while SVCV and CyHV-3 were negative in the assay. The CyHV-2 was also detected in asymptomatic Prussian carp. Sequence analysis of the CyHV-2 DNA polymerase and helicase genes revealed high similarity to previously reported strains from Serbia and other countries. The occurrence of these outbreaks in Prussian carp populations in lakes indicates the probable spread of the virus within freshwater ecosystems in Serbia, potentially impacting the degradation of aquatic habitats.

Microalgae-mediated bioremediation: Metabolomic profiling and adaptive responses under amoxicillin-induced stress

This study examines the effects of varying concentrations (25, 50, 100, and 150 mg/L) of Amoxicillin-3000 (AMOX), a widely prescribed beta-lactam antibiotic, on the growth of the microalga Chlorella sorokiniana UUIND6. Results revealed that low AMOX concentration (25 mg/L) stimulated best algal growth, prompting further exploration of AMOX degradation processes, identification of transformation products, biochemical composition of microalgae. Photodegradation, both direct (light) and indirect (induced by microalgae) was examined. LCMS identified similar transformation product in both the photodegradation with a m/z ratio of 367.1. Moreover, microalgae-induced c photodegradation resulted in negligible zone of inhibition after 96 h, achieving an impressive 98.8 % degradation, significantly surpassing the 85.5 % degradation observed with light alone. Modifications in abiotic factors also influence the stoichiometry of microalgae cells, resulting in significantly higher lipid (31.24 ± 2.93 %) and protein (44.12 ± 1.75 %) content compared to control cells (lipid 23.6 ± 2.4 %, protein 31.62 ± 1.52 %), indicating notable metabolic alterations (p<0.05) under AMOX-induced stress. Additionally, increased reactive oxygen species (ROS) scavenging activity (48.89 ± 2.51 %) suggests photosynthetic impairment and a decrease in TPC and TFC content, aiding in the prevention of oxidative stress. Overall, this study highlights the advantages of Chlorella-induced bioremediation of AMOX via photodegradation over light-driven processes. It presents a practical, sustainable approach for mitigating ecological risks in freshwater ecosystems and provides insights into antibiotic removal mechanisms and performance in microalgae-based systems under environmentally relevant conditions.

Spatial Distribution of Calanoida in Freshwater Ecosystems and Their Application as a Food Web Assessment Index

Calanoida is a representative oligo-mesotrophic indicator species, frequently used as an index for assessing lake ecosystems’ health. Additionally, they function as trophic intermediates in the food web, connecting primary producers and higher consumers within lake ecosystems’ food chains. However, research cases that present the implications of habitat environment assessments, such as ecosystem structure and water quality, represented by these taxa remain insufficient. In this study, we conducted research across 49 lakes in South Korea, analyzing the occurrence characteristics of Calanoida and examining the correlations between Calanoida abundance and water quality parameters and the morphological-based functional groups of phytoplankton. Calanoida were more frequently observed in lakes characterized by greater size, increased depth, and reduced levels of anthropogenic land use. Furthermore, Calanoida occurrence was more probable in environments characterized by lower electrical conductivity and suspended solids concentrations. Their presence was also associated with conditions where Large mucilaginous phytoplankton (MBFG7), which includes cyanobacteria, and Large filamentous phytoplankton (MBFG3) were prevalent. An analysis of the environmental factors influencing the increase in Calanoida abundance revealed an inverse relationship between their abundance and water quality factors, including nutrient levels. This trend was observed consistently across all genera. Additionally, Calanoida were observed to maintain a high abundance in environments where the presence of the Large mucilaginous phytoplankton group (MBFG7) was relatively high. In contrast, Cyclopoida exhibited varying occurrence characteristics by genus in response to different water quality factors. Based on these results, we suggest that Calanoida, commonly used as an indicator of mesotrophic conditions, can also serve as a valuable indicator for evaluating the functionality of the food web. While Calanoida struggle to inhabit environments characterized by degraded water quality, they demonstrate the ability to adapt and persist in environments containing large, mucilaginous, or filamentous phytoplankton species that are typically challenging for other zooplankton to graze.

Glitters in fishing ground baits – A direct source of primary microplastics in soil and freshwater ecosystems

The aim of this paper is to draw attention to the direct source of primary microplastics (MPs) that have been entirely neglected so far, namely by providing qualitative studies of the fishing ground baits with glitters. Among many microplastic sources already detected in fishing and angling gear and reported in the literature, the glitters in synthetic pastry are the only primary source (produced <5 mm; P-MPs), with MPs placed directly into the freshwater, during sports competitions and individual leisure activities, and were so far not discussed. Dozens of different fishbait pastry products available on the market containing glitters were funded to represent, from the material point of view, only three different classes studied further. Fourier-transform infrared (FTIR), ATR-FTIR and Raman spectroscopy combined with scanning electron microscopy with an energy-dispersive detector (SEM/EDS) enabled the characterization of their composition and morphology. Glitters are composite structures with an internal core and several chemical layers symmetrically placed on both sides. The polymer origin of particles, with the polyethylene terephthalate (PET) core, was confirmed as being an essential condition to classify them as P-MPs. One should focus on the fact that those primary microplastics are designed purposely to be particularly attractive and ingested by fishes, thus being efficiently introduced to the trophic chain with all persistent consequences, including their contribution to the plastisphere. The preliminary qualitative results of environmental stability were obtained in the accelerated ageing test to discuss the possible long-term ecological implications further. Glitters were durable in the saltwater (both natural and used for weathering in the ageing chamber) and in the seabed sediments. The primary weathering test was performed in marine environments, as oceans are the final destination of most freshwater MPs. Finally, suggestions for future studies to enlarge the knowledge about this issue are provided.

Diving into diversity: aquatic beetles of Sukhna Wildlife Sanctuary, Chandigarh, India

The Sukhna Wildlife Sanctuary, located in the Shivalik Hills of Chandigarh, India, encompasses several freshwater ecosystems, including ponds, streams, and marshes. The objective of this study is to fill the current information void regarding the populations of aquatic beetles in the sanctuary. During the period from June to September 2023, a comprehensive study was conducted in the Sukhna Wildlife Sanctuary, resulting in the identification and documentation of 164 specimens of aquatic Coleoptera. These specimens belonged to six species, five genera, and two families in which the Dytiscidae family was found to be the most prevalent. The study findings offer significant insights into the population magnitude and geographical dispersion of aquatic beetles within the investigated settings and show the need for comprehensive surveys to understand the intricate interplay of factors governing beetle distribution.