Freshwater Aquatic Environments Research Articles

Synthetic Microplastics in UK tap and bottled water; Implications for human exposure

There is increasing concern for public health over inadvertent human exposure to MPs due to potential adverse health effects linked to MPs polymeric composition, toxic chemical additives, and/or harmful microorganisms adsorbing onto their surfaces. While numerous studies have reported MPs occurrence and risk in the freshwater aquatic environment and drinking water sources (e.g., rivers, lakes, and reservoirs), the current state-of-knowledge on MPs pollution in drinking water (i.e., tap water and bottled water) remains limited at a global level. This paper provides the first comprehensive study of the occurrence, concentrations, size distribution, shape, and polymer type of MPs in 177 tap water samples from 13 cities in the United Kingdom, as well as 85 samples of bottled water from 17 popular brands, with various packaging materials, on the UK market.MPs were detected in all tap water samples (range 6–100 MP/L) and bottled water samples (range 12–62 MP/L). Average MPs concentration in tap water (40 ± 16 MP/L) was statistically indistinguishable from that in bottled water (37 ± 11 MP/L). However, the average MPs particle size in tap water (32.4 μm) exceeded significantly (p < 0.05) that in bottled water (26.5 μm), indicating the various purification processes applied to bottled water may help remove larger MPs, but raises concern over the potential adverse health effects from exposure to smaller MPs. The most frequently detected polymer types were: polypropylene (PP), polyethylene (PE), and polyvinyl chloride (PVC) in tap water, and PE, PP and polyethylene terephthalate (PET) in bottled water. A strong correlation was observed (r = 0.68, P = 0.049) between the plastic cap material (PE) and the predominant polymer type in the bottled water. In terms of morphology, fragments and fibres were the most abundant MPs, together constituting 92 % and 96 % of MPs detected in tap and bottled water samples, respectively.Using EFSA (European Food Safety Authority) recommended daily water intakes, the corresponding exposures to MPs in different UK age groups were estimated. On a body weight (BW) basis, infants and toddlers were exposed (4 MP/kg BW/day) at a higher level than adults (1 MP/kg BW/day). This raises concern, given the former's incompletely developed immune/nervous systems rendering them at higher risk of adverse health effects from such exposure.

Description of the wing spur in the subfossil Malagasy lapwing, Vanellus madagascariensis (Aves: Charadriiformes, Charadriidae): Insights into some of its possible life history traits and why it is extinct

We report on a subfossil carpometacarpus of an extinct species of lapwing, Vanellus madagascariensis, restricted to Madagascar and inferred to be less than 3,000 years old. Lapwings, comprising 24 species in the New and Old World, are not recorded in the modern Malagasy avifauna. Members of this genus are often well-adapted to human induced habitat modifications. Material of this species has been recovered from three subfossil sites, each site with a single element, in the southwest of the island, including two humeri and a carpometacarpus. The carpal spur of V. madagascariensis was notably more developed than any living species of lapwing. It is presumed that these formidable armaments were employed to defend territories and hinder predation on nest contents and young. Large-scale desiccation in southwestern Madagascar starting about 3,000 years ago would have had a direct impact on local freshwater aquatic environments, in turn diminishing local habitat for this species, and ultimately leading to its extinction.

Assessing the relevance of environmental exposure data sets.

Environmental exposure data are used by decision-makers to assess environmental risks and implement actions to mitigate risks from contaminants. The first article in this series summarized the available evaluation schemes for environmental exposure data, of which there are few compared to those available for environmental hazard data. The second article covered the assessment of the reliability of environmental exposure data sets under the Criteria for the Reporting and Evaluation of Exposure Data (CREED). The aim of this article is to provide an overview and practical guidance on the relevance assessment in the context of the CREED approach for evaluating exposure monitoring data sets. Systematically considering relevance is critical for both evaluating existing data sets and for optimizing the design of new monitoring studies. Relevance is defined here as the degree of suitability or appropriateness of a data set to address a specific purpose or to answer the questions that have been defined by the assessor or for those generating exposure data. The purpose definition will be the foundation for the relevance assessment, to clarify how the assessor should rate the assessment criteria (fully met, partly met, not met/inappropriate, not reported, not applicable). This will provide transparency for anyone reviewing the outcomes. An explicit gap analysis (i.e., an articulation of the data set limitations for the stated purpose) is an important outcome of the relevance assessment. The relevance evaluation approach is demonstrated with three case studies, all relating to the freshwater aquatic environment, where the data sets are scored as relevant with or without restrictions, not relevant, or not assignable. The case studies represent both organic and inorganic constituents, and have different data characteristics (e.g., percentage of censored data, sampling frequencies, relation to supporting parameters). Integr Environ Assess Manag 2024;20:1004-1018. © 2023 SETAC.

Nile red staining of polyethylene and polystyrene in Daphnia magna tests

Microplastics pollution represents a stringent global issue. Their accumulation in the aquatic environment remains complicated due to the abundance, distribution, and resulting environmental effects they induce. Recently, assessing the toxicity level of aquatic organisms has gained scientific interest. Due to the diverse types and sizes of polymers present in the environment, the detection and evaluation of their effects are still a challenging issue. Polyethylene (PE) and polystyrene (PS) are the most commonly used polymers and are therefore predominantly detected in both marine and freshwater aquatic environments. This paper aims to evaluate the effects of Red Nile-stained PE and PS, tested in different particle sizes (PE 40-48, 125, &gt;125 µm, and PS 20, 200, 430 µm) on Daphnia magna, and highlight them through microscopic analysis. Acute toxicity tests conducted over a 48-hours exposure did not reveal significant toxicity effects in terms of mortalities compared to the controls. Red Nile staining allowed the visualization of the shapes and sizes of the tested microplastics and their entry pathways into the Daphnia bodies. PS of 20 µm size was detected in the digestive tract of Daphnia, indicating as primary pathway of entry into the body of aquatic organisms. No acute toxic effects were recorded as a result of direct exposure to PE and PS particles. However, sub-lethal effects such as feeding and growth disturbances, which could affect organisms in the long term, are suspected.

Toxic effects of environmentally relevant concentrations of naproxen exposure on Daphnia magna including antioxidant system, development, and reproduction

Naproxen (NPX) is one of common non-prescription non-steroidal anti-inflammatory drugs (NSAIDs) which is widely detected in aquatic environments worldwide due to its high usage and low degradation. NPX exerts anti-inflammatory and analgesic pharmacological effects through the inhibition of prostaglandin-endoperoxide synthase (PTGS), also known as cyclooxygenase (COX). Given its evolutionarily relatively conserved biological functions, the potential toxic effects of NPX on non-target aquatic organisms deserve more attention. However, the ecotoxicological studies of NPX mainly focused on its acute toxic effects under higher concentrations while the chronic toxic effects under realistic concentrations exposure, especially for the underlying molecular mechanisms still remain unclear. In the present study, Daphnia magna, being widely distributed in freshwater aquatic environments, was selected to investigate the toxic effects of environmentally relevant concentrations of NPX via determining the response of the Nrf2/Keap1 signaling pathway-mediated antioxidant system in acute exposure, as well as the changes in life-history traits, such as growth, reproduction, and behavior in chronic exposure. The results showed that the short-term exposure to NPX (24 h and 48 h) suppressed ptgs2 expression while activating Nrf2/Keap1 signaling pathway and its downstream antioxidant genes (ho-1, sod, cat and trxr). However, with prolonged exposure to 96 h, the opposite performance was observed, the accumulation of malondialdehyde (MDA) indicated that D. magna suffered from severe oxidative stress. To maintain homeostasis, the exposed organism may trigger ferroptosis and apoptosis processes with the help of Silent mating type information regulation 2 homologs (SIRTs). The long-term chronic exposure to NPX (21 days) caused toxic effects on D. magna at the individual and population levels, including growth, reproduction and behavior, which may be closely related to the oxidative stress induced by the drug. The present study suggested that more attention should be paid to the ecological risk assessment of NSAIDs including NPX on aquatic non-target organisms.

Molecular Footprints on Osmoregulation-Related Genes Associated with Freshwater Colonization by Cetaceans and Sirenians.

The genetic basis underlying adaptive physiological mechanisms has been extensively explored in mammals after colonizing the seas. However, independent lineages of aquatic mammals exhibit complex patterns of secondary colonization in freshwater environments. This change in habitat represents new osmotic challenges, and additional changes in key systems, such as the osmoregulatory system, are expected. Here, we studied the selective regime on coding and regulatory regions of 20 genes related to the osmoregulation system in strict aquatic mammals from independent evolutionary lineages, cetaceans, and sirenians, with representatives in marine and freshwater aquatic environments. We identified positive selection signals in genes encoding the protein vasopressin (AVP) in mammalian lineages with secondary colonization in the fluvial environment and in aquaporins for lineages inhabiting the marine and fluvial environments. A greater number of sites with positive selection signals were found for the dolphin species compared to the Amazonian manatee. Only the AQP5 and AVP genes showed selection signals in more than one independent lineage of these mammals. Furthermore, the vasopressin gene tree indicates greater similarity in river dolphin sequences despite the independence of their lineages based on the species tree. Patterns of distribution and enrichment of Transcription Factors in the promoter regions of target genes were analyzed and appear to be phylogenetically conserved among sister species. We found accelerated evolution signs in genes ACE, AQP1, AQP5, AQP7, AVP, NPP4, and NPR1 for the fluvial mammals. Together, these results allow a greater understanding of the molecular bases of the evolution of genes responsible for osmotic control in aquatic mammals.

In vitro and in vivo anti-oomycetes activities and mechanisms of linalool against Saprolegnia ferax

Saprolegnia ferax (S. ferax) is one of the most highly pathogenic oomycetes species in freshwater aquatic environments causing serious saprolegniosis. Linalool is a kind of natural alternative of antibiotics existing in various plants essential oils. In this study, the in vitro and in vivo anti-oomycetes activity and mode of action of linalool against S. ferax CQT1 were investigated. For in vitro test, linalool exhibited mycelium growth and zoospore production inhibition at 0.1% (v/v, 0.862 mg/ml) and 0.025% (v/v, 0.216 mg/ml), respectively. The mycelium was wrinkled, deformed, and shrunken after treatment with linalool. Linalool altered membrane permeability, caused permanent damage, or membrane breakdown. Further, the transcriptomic analysis showed that: (1) Linalool affected the oxidation and metabolism of fatty acids, leading to mitochondrial dysfunction and the inhibition of energy supply. (2) The increase in glycerophospholipid metabolism is probably the cell response to deal with cellular damage. (3) The degradation of branched chain amino acids may inhibit amino acid metabolism and result in the dysfunction of protein synthesis. (4) ABC transporters contribute to metabolic resistance to linalool and efflux of linalool outside of cells. For in vivo test, the cumulative survival rate of grass carp treated with linalool was significantly higher than those untreated with linalool, moreover, microscopic histopathology analysis results showed that there was robust mucus cell density in fish skin, the dermis and epidermis were relatively intact after linalool treatment. In all, our findings would provide foundations for the potential use of linalool to prevent and control S. ferax infection in the aquaculture industry.

Multi-isotopic analysis reveals the early stem turtle Odontochelys as a nearshore herbivorous forager

IntroductionAfter decades of debate on the origin of turtles, it is now widely accepted that they are diapsid reptiles originating in the Permian from a terrestrial ancestor. It seems that the initial development of the structures that will later form the unique turtle bony shell took place as a response to a fossorial lifestyle. However, the earliest stem turtle with a fully complete plastron, Odontochelys semitestacea from the Late Triassic (lower Carnian) of China, is somewhat controversially interpreted as an aquatic or even a marine form, raising the question of the environment in which the completion of the plastron happened.MethodsHere, we analyzed the stable carbon, oxygen and sulfur isotope compositions (δ13C, δ18O and δ34S) of bones from two specimens of Odontochelys along with bones and teeth of two associated specimens of the marine ichthyosaur Guizhouichthyosaurus tangae.Results and discussionWe first show that δ18O values of Odontochelys are incompatible with a terrestrial lifestyle and imply a semi-aquatic to aquatic lifestyle. Isotopic results also demonstrate that the aquatic environment of Odontochelys was submitted to a strong marine influence, therefore excluding the possibility of a strict freshwater aquatic environment. Additionally, an unusual carbon isotope composition shows that O. semitestacea was herbivorous, probably consuming macrophytic algae in coastal zones like the extant green sea turtle (Chelonia mydas) or the marine iguana (Amblyrhynchus cristatus) do.

Adverse effects of iron-based nanoparticles on freshwater phytoplankton Scenedesmus armatus and Microcystis aeruginosa strains

Zero-valent nano-iron particles (nZVI) are increasingly present in freshwater aquatic environments due to their numerous applications in environmental remediation. However, despite the broad benefits associated with the use and development of nZVI nanoparticles, the potential risks of introducing them into the aquatic environment need to be considered. Special attention should be focused on primary producer organisms, the basal trophic level, whose impact affects the rest of the food web. Although there are numerous acute studies on the acute effects of these nanoparticles on photosynthetic primary producers, few studies focus on long-term exposures. The present study aimed at assessing the effects of nZVI on growth rate, photosynthesis activity, and reactive oxygen activity (ROS) on the freshwater green algae Scenedesmus armatus and the cyanobacteria Microcystis aeruginosa. Moreover, microcystin production was also evaluated. These parameters were assessed on both organisms singly exposed to 72 h-effective nZVI concentration for 10% maximal response for 28 days. The results showed that the cell growth rate of S. armatus was initially significantly altered and progressively reached control-like values at 28 days post-exposure, while M. aeruginosa did not show any significant difference concerning control values at any time. In both strains dark respiration (R) increased, unlike net photosynthesis (Pn), while gross photosynthesis (Pg) only slightly increased at 7 days of exposure and then became equal to control values at 28 days of exposure. The nZVI nanoparticles generated ROS progressively during the 28 days of exposure in both strains, although their formation was significantly higher on green algae than on cyanobacteria. These data can provide additional information to further investigate the potential risks of nZVI and ultimately help decision-makers make better informed decisions regarding the use of nZVI for environmental remediation.

The Effects of Preservatives on Antibiotic- and Preservative-Resistant Microbes and Nitrogen/Sulfur Cycle Associated Microbial Communities in Freshwater River Sediments.

The intensive use of benzoic acid (BA), 4-hydroxybenzoic acid (HB), and dehydroacetate (DHA) as additives and preservatives in cosmetics and foods causes emerging environmental pollutions. Anthropogenic releases of BA, HB and DHA are primarily emissions into water and soil. However, few studies investigate the effects of BA, HB and DHA on microbial communities in freshwater river sediments. The aim of this study is to reveal the effects of BA, HB and DHA on microbial communities in freshwater river sediments. Tetracycline-, sulfamethoxazole- and preservative-resistant microbes were increased in the river sediments treated with BA, HB and DHA. The relative abundances of methanogen- and xenobiotic-degradation-associated microbial communities were also increased in the BA-, HB- and DHA-treated sediments. The relative abundance of four nitrogen cycle associated microbial groups (anammox, nitrogen fixation, denitrification, and dissimilatory nitrate reduction) were increased after the eighth week in the BA-, HB- and DHA-treated sediments. For the sulfur cycle, the relative abundance of thiosulfate oxidation associated microbial communities were increased after the eighth week in the BA-, HB- and DHA-treated sediments. Results of this study provide insight into the effects of BA, HB and DHA on antibiotic resistance, nitrogen cycle, sulfur cycle, drug resistance and methane production in freshwater aquatic environments.

Impacts of ZnO and multi-walled carbon nanotubes (MWCNTs) on biological parameters of the Oriental river prawn Macrobrachium nipponense De Haan, 1849 (Decapoda: Caridea: Palaemonidae)

Abstract Nanomaterials (NMs) mainly settle on bottom sediments and accumulate in the benthos of aquatic communities. Decapod crustaceans, being deposit-omnivorous feeders, are appropriate biological models to assay the biological effects of NMs. The present study evaluated the effects of ZnO and multi-walled carbon nanotubes (MWCNTs) NMs separately and in combination on the activities of antioxidant enzymes on crustacean hyperglycemic hormone (CHH), hematology, reproductive performance, and hepatopancreas lesions the Oriental river prawn, Macrobrachium nipponense De Haan, 1849 [De Haan, 1833–1850]. We essayed concentrations of ZnO (0, 1, 10, 30, 50 mg l–1) and MWCNTs (0, 5, 10, 15, 20 mg l–1) and two higher concentrations of the NMs were compared in combined treatments. Both NMs showed dose-dependent effects on reproductive parameters of M. nipponense, especially the fertilization rate of eggs. Inter-molt and inter-spawn periods were postponed and reproduction stopped in 50 ppm ZnO and 15 and 20 ppm MWCNTs treatments. Our findings showed that the release of crustacean hyperglycemic hormone (CHH) and superoxide dismutase (SOD) enzyme activity are directly related to the NMs levels independently as well as in combination. NMs did not show any effect on the activities of alanine transaminase (ALT) and aspartate transaminase (AST) enzymes in muscle tissue independently, but the combined effects of the activities of these enzymes were significant. NMs caused hepatocyte enlargement, melanization, apoptosis, and necrosis damages in the hepatopancreas of prawns. The findings showed that ZnO and MWCNTs NMs have strong adverse biological effects on M. nipponense, and that this species is an appropriate bio-indicator and bio-monitor organism for NMs contaminations in the freshwater aquatic environments.

Isolation and characterization of algicidal bacteria from freshwater aquatic environments in China.

Algicidal bacteria can inhibit the growth of algae or lyse algal cells, thus playing roles in shaping aquatic microbial communities and maintaining the functions of aquatic ecosystems. Nevertheless, our understanding of their diversities and distributions remains limited. In this study, we collected water samples from 17 freshwater sites in 14 cities in China and screened a total of 77 algicidal bacterial strains using several prokaryotic cyanobacteria and eukaryotic algae as target strains. According to their target-specificities, these strains were classified into three subgroups, cyanobacterial algicidal bacteria, algal algicidal bacteria, and broad-target algicidal bacteria, each displaying distinctive compositions and geographical distribution patterns. They are assigned to Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes bacterial phyla, of which Pseudomonas and Bacillus are the most abundant gram-negative and gram-positive genus, respectively. A number of bacterial strains, such as Inhella inkyongensis and Massilia eburnean, are suggested as new algicidal bacteria. The diverse taxonomies, algal-inhibiting abilities and distributions of these isolates have suggested that there are rich algicidal bacterial resources in these aquatic environments. Our results provide new microbial resources for algal-bacterial interaction studies, and shed new insights into how algicidal bacteria can be used in the control of harmful algal blooms, as well as in algal biotechnology.

The potential ecological risk of veterinary pharmaceuticals from swine wastewater on freshwater aquatic environment

The impact of pharmaceutical residue transport in the aquatic ecosystem has become an increasing subject of environmental interest due to the inherent bioactivity of trace levels of antibiotics and the negative environmental and public health impact. In this study, three veterinary pharmaceuticals including tetracycline, ivermectin, and salicylic acid were investigated in a piggery effluent from Western Cape, South Africa. Three freshwater organisms' taxonomic groups (Pseudokirchneriella subcapitata, Daphnia magna, and Tetrahymena thermophila) were used to determine the ecological risk of different treated piggery effluent concentration range of 1%, 10%, and 20% and a cocktail mixture of veterinary pharmaceuticals of environmental concerns. The average concentration of veterinary pharmaceuticals was in the range of 47.35, 7.19, and 1.46 μg L-1 for salicylic acid, chloro-tetracycline, and ivermectin, respectively. P.subcapitata exposed to 20% piggery wastewater effluent at 24- and 48-h EC50 showed a toxicity value of 14.2% and 13.6% (v/v), respectively. The study established the ecological risk of the test compounds as low to medium risk for low-level dose and low concentrations of piggery effluent. The relative sensitivity ranking of the taxa drawn is microalgae > protozoa > Cladocera. The study results demonstrated that a high dose of piggery effluent and mixtures of veterinary pharmaceutical can pose a high risk in freshwater ecosystems. PRACTITIONER POINTS: Transport processes of veterinary antibiotics into the environment were investigated. Dilution effect of the veterinary pharmaceutical on the antibiotic levels exists. High dose of piggery effluent presented an ecological risk.

Environmental and immunonutrition effects on public health linked to water pollutants and fish disease

Freshwater aquatic environment are indeed in a bad state worldwide, due to human activities and there is an urgent need to save them and their biodiversity. Water plays a key role in diluting pollutants and because of that superiority as a solvent, it also means that water-soluble wastes pollute water easily. For instance, runoff from nearby lands provides freshwater life zones with an almost constant input of organic material, inorganic nutrients, and other pollutants. These cause undesirable changes in the physicochemical or biological factors of ecosystem, which in turn directly or indirectly affect the ecological balance of the environment, and ultimately affect human beings. And also advances in culture techniques and the introduction of new species have contributed to the rapid growth of the aquaculture industry. However, treatment methods including approved antibiotics and chemotherapeutants are directly or indirectly affected the consumer/environment-friendly. This review paper tried to indicate how agricultural activities and unbalanced fish nutrition affect fish health and water quality at large the environment.

Denticula, Hantzschia and Tryblionella (Bacillariaceae, Bacillariophyta) from northwestern Ceará freshwaters

Abstract Diatoms constitute a representative portion of the algal community of freshwater aquatic environments, but their studies are centered mostly in the south and southern regions of Brazil, making the microalgae biodiversity of water bodies in the semiarid practically unknown. In the state of Ceará, the few records of the Bacillariaceae are centered in the southern region of the state and are generally not identified at specific level. Denticula, Hantzschia, and Tryblionella are worldwide distributed diatom genera that belong to the family Bacillariaceae. The group is characterized by raphe located on a channel, internally supported by silica extensions, the fibulae. This is a taxonomic study on the genera Denticula, Hantzschia, and Tryblionella found in water bodies in northwestern Ceará state. Planktonic and periphytic samples were collected in four hydrographic basins, which are influenced by the semiarid climate, located in northwestern Ceará, northeastern Brazil. Fourteen infrageneric taxa were identified, described, and illustrated, all being pioneer citations for Ceará. The present study highlighted the underestimated diversity of diatoms in the semiarid region of Ceará and the need to cover undersampled or never explored regions to significantly contribute to the knowledge of the diatom flora and its distribution in Brazilian aquatic environments.

Abundance and biofilm formation capability of Vibrio cholerae in aquatic environment with an emphasis on Hilsha fish (Tenualosa ilisha).

The potentially deadly and sporadic diarrhea-causing agent, Vibrio cholerae, is present in a great number in the freshwater aquatic environment and can be transmitted to humans by different aquatic organisms. In the perspective of Bangladesh, an anadromous fish species Hilsha (Tenualosa ilisha) can act as a transmission vehicle of V. cholerae from the aquatic to the household kitchen environment. The present study was carried out to investigate the presence of V. cholerae in the aquatic habitat of Bangladesh with a major emphasis on freshly caught Hilsha fish, along with river water and plankton samples from the fish capture site. The study also detected the biofilm formation capability of V. cholerae within Hilsha fish that might help the transmission and persistence of the pathogen in aquatic habitat. Twenty out of 65 freshly caught fish (30.8%) and 1 out of 15 water samples (6.67%) showed the presence of V. cholerae and none of the plankton samples were positive for V. cholerae. The isolated strains were identified as non-O1 and non-O139 serogroups of V. cholerae and contain some major toxin and virulence genes. A few strains showed cellular cytotoxicity on the HeLa cell line. All strains were able to form biofilm on the microtiter plate and the detection of three genes related to biofilm formation (vpsA, vpsL, and vpsR) were also assayed using qPCR. In this study, the in vitro biofilm formation ability of the isolated strains may indicate the long-term persistence of V. cholerae in different parts of Hilsha fish. The abundance of V. cholerae only in freshly caught Hilsha fish and the absence of the pathogen in the surrounding aquatic environment could stipulate the role of Hilsha fish as one of the major transmission routes of V. cholerae from the freshwater aquatic environment of Bangladesh to the household kitchen environment.

Diversity and longitudinal dynamics of benthic macro-invertebrate populations in the shallow zone of the Chari River at Sarh (Chad, Central Africa)

The biology of Chadian freshwater aquatic environments is little known and works on benthic macroinvertebrates dates back to at least the 1980s thanks to the work of the office for scientific and technical research overseas (ORSTOM). This study was carried out in the Chari River, Bahr Kôh Department (Moyen Chari) over a distance of 52 km on the edge of the town of Sarh in order to assess the family diversity of macroinvertebrates. Sampling was carried out in shallow environments with a weak current. A haze net constituted of a 1 m long sleeve and a collector with a circular opening of 30 cm diameter and a mesh size of 500 µm was used following the multi-habitat approach according to the Barbourt method adapted by Stark. Sampling was carried out on a monthly basis during the flood period from August to November 2020, which corresponds to the period of maximum lateral expansion of the Chari, and during the low-water period from February to May 2021, which corresponds to the period when the water level of the Chari reached its lowest point. The fauna surveyed is composed of 10464 individuals belonging to 98 families, 17 orders and 7 classes. Insects are the most represented and constitute 76.53% of the total richness of the macrofauna collected, followed by molluscs composed of 13.26%, including 9.18% of gastropods. Annelids, Crustacea and Chelicerata were the groups with the lowest number of individuals (of the population). Chironomidae and Dytiscidae had the highest total family richness, while Thiaridae was the most abundant family. The Kruskal-wallis test was applied to explain the good spatiotemporal diversity of the stands. Depending on the season, low diversity was observed at the end of low water and during high water. The high taxonomic richness of the entomofauna, dominated by pollutants, at stations where human activities are taking place indicates a state of disturbance linked to pollution. While the spatial distribution of total abundance was dominated by Molluscs (Thiaridae, Corbiculidae) in the downstream stations is explained by the mineralisation and enrichment in organic matter of these stations.

Integrative description of changes occurring on zebrafish embryos exposed to water-soluble crude oil components and its mixture with a chemical surfactant

The effects of crude oil spills are an ongoing problem for wildlife and human health in both marine and freshwater aquatic environments. Bioassays of model organisms are a convenient way to assess the potential risks of the substances involved in oil spills. Zebrafish embryos (ZFE) are a useful to reach a fast and detailed description of the toxicity of the pollutants, including both the components of the crude oil itself and substances that are commonly used for crude oil spill mitigation (e.g. surfactants). Here, we evaluated the survival rate, as well as histological, morphological, and proteomic changes in ZFE exposed to Water Accumulated Fraction (WAF) of light crude oil and in mixture with Dioctyl Sulfosuccinate Sodium (DOSS, e.g. CEWAF: Chemically Enhanced WAF), a surfactant that is frequently used in chemical dispersant formulations. Furthermore, we compared the hydrocarbon concentration of WAF and CEWAF of the sublethal dilution. In histological, morphological, and gene expression variables, the ZFE exposed to WAF showed less changes than those exposed to CEWAF. Proteomic changes were more dramatic in ZFE exposed to WAF, with important alterations in spliceosomal and ribosomal proteins, as well as proteins related to eye and retinal photoreceptor development and heart function. We also found that the concentration of high molecular weight hydrocarbons in water was slighly higher in presence of DOSS, but the low molecular weight hydrocarbons concentration was higher in WAF. These results provide an important starting point for identifying useful crude-oil exposure biomarkers in fish species.

Microplastics in fresh- and wastewater are potential contributors to antibiotic resistance - A minireview

Increasing antibiotic resistance and microplastic (MP) pollution are among the global environmental challenges of our time. This study reviews relevant studies on MP pollution and the abundance of antibiotic resistant elements in freshwater resources. The objective was to evaluate the potential antibiotic resistance spread via MPs in the freshwater aquatic environment. Studies have indicated that MPs interact with microbial communities differently than natural particles, harboring a unique bacterial community than the surrounding water. The composition of MP biofilm community revealed an abundance of bacterial cells, pathogens, antibiotic resistant genes (ARGs) and mobile genetic elements (MGEs). The closely packed bacterial cells in MP biofilm in a water matrix might offer a favorable enviroment for horizontal genes transfer (HGT). Furthermore, antibiotics in trace concentrations in freshwater resources could be adsorbed onto MP surfaces and impact the microbial composition by selective enrichment of antibiotic resistant bacteria (ARB). The biofilm matrix provide protection in MP biofilms that could impact the disinfection efficiency of conventional treatment techniques. The impacts of MPs, antibiotic resistant elements and their interaction on human health and aquatic biota remain relatively unknown to date. Future studies on MPs and antibiotic resistant elements need to consider the collective role, challenges, and consequences of the interaction between MPs and antibiotic resistant elements in freshwater ecosystem.

Evaluation of Nutraceutical Properties of Eleven Microalgal Strains Isolated from Different Freshwater Aquatic Environments: Perspectives for Their Application as Nutraceuticals

The increasing global population and the simultaneous growing attention to natural, sustainable, and healthier products are driving the food industry towards research on alternative food sources. In this scenario, microalgae are gaining worldwide attention as “functional feedstocks” for foods, feeds, supplements, and nutraceutical formulations, being a source of high-value metabolites including polyphenols and other antioxidant compounds. In this work, eleven microalgal strains from freshwater environments were evaluated for their nutraceutical properties, focusing on photosynthetic pigments, total polyphenols, and flavonoid content, as well as in vitro antioxidant activities. Data helped to select those strains showing the most promising features for simultaneous massive growth and bioactive compound production. Results highlighted that the microalgae have variable values for both biochemical parameters and antioxidant activities, mainly depending on the solvents and applied treatment rather than on the isolation sources or the phylogenetic attribution. According to our results, the putative best candidates for massive cultivation under laboratory conditions for the simultaneous extraction of different molecules with nutraceutical potential are strains F1 (Scenedesmaceae), F3 (Chlamydomonas debariana), R1 (Chlorella sorokiniana), and C2 (Chlorella-like).