Search Results (452)

Hypoxia and salinization increasingly co-occur in freshwater and estuarine ecosystems, yet their combined effects under fluctuating oxygen regimes remain poorly resolved. We experimentally quantified survival responses of four planktonic crustaceans (Daphnia magna, Daphnia longispina, Eurytemora velox, and Thermocyclops crassus) along a salinity gradient expressed as conductivity (0.6–7.7 mS cm⁻¹) under two oxygen regimes: sustained hypoxia and repeated short-term hypoxia over 120 h, under standardized food-deprived conditions to isolate abiotic stress effects. Under sustained hypoxia, survival declined monotonically with decreasing oxygen in all species, with marked interspecific differences at ≤2 mg L⁻¹. Under fluctuating oxygen conditions, survival peaked at low to intermediate salinity and declined sharply at elevated salinity, indicating a strong combined effect of oxygen limitation and salinity-related stress. Multivariate analysis identified a significant salinity × oxygen interaction, indicating that the effect of oxygen depletion on survival depended on salinity. Daphnia magna showed the highest tolerance, whereas D. longispina and E. velox were highly sensitive to elevated salinity; T. crassus showed intermediate tolerance. These results indicate that elevated salinity is associated with negative effects under both sustained and episodic hypoxia and that fluctuating oxygen regimes elicit strong combined stress responses. Our findings highlight the importance of combined abiotic stress effects when predicting zooplankton responses in oxygen-depleted and salinizing aquatic ecosystems. Full article

The proliferation of daphnids in secondary clarifiers of urban wastewater treatment plants (WWTPs) can compromise effluent quality and disrupt treatment stability. This study evaluated the effectiveness of sodium hypochlorite (NaOCl) for controlling daphnid populations and assessed its influence on dormant eggs hatching. A pilot-scale oxidation ditch activated sludge system was operated under conditions simulating a full-scale WWTP. Acute toxicity tests were performed in clarified water (CW) and mixed liquor (ML) using NaOCl concentrations between 0.76 and 5 mg L⁻¹, with mortality monitored over 96 h and LC₅₀ values determined. In CW, concentrations ≥ 3.125 mg L⁻¹ caused 100% mortality within 24 h (24 h LC₅₀ = 1.75 mg L⁻¹). In ML, toxicity was significantly reduced (24 h LC₅₀ = 7.43 mg L⁻¹). Statistical analysis confirmed NaOCl concentration as the main driver of mortality, with additional contributions from operational parameters such as electrical conductivity, total dissolved solids, and dissolved oxygen. Hatching assays revealed that higher NaOCl concentrations and prior cold exposure (4 °C) increased ephippia hatching, reaching 40% under combined conditions. Although NaOCl effectively inhibits active organisms, it may stimulate dormant egg hatching, potentially sustaining populations. Optimized control strategies are therefore required to ensure effective and sustainable daphnid management in WWTPs. Full article

Daphnids, commonly known as water fleas, are freshwater planktonic microcrustacean species used as model organisms in ecotoxicology, particularly in regulatory frameworks that adhere to OECD and ISO standards. Mortality is the most common endpoint in toxicity testing; however, more sensitive indicators are required to assess sublethal acute effects of pollutants. The use of feeding impairment as a toxicity phenotypic endpoint in daphnids is considered a cost-effective approach that aligns with the 3Rs principle (Replace, Reduce, Refine) and is more physiologically and environmentally relevant. Current feeding methods are inefficient due to the large test volumes and extended incubation periods required. In this paper, we present a miniaturised protocol to assess feeding behaviour following exposure to chemicals in daphnids. The method is based on the consumption of algae, which is measured with chlorophyll fluorescence. The optimised protocol is more robust and rapid, and results can be obtained in 30 min and in a 96-well plate. Responses in feeding rate were investigated using this miniaturised protocol following exposure to a range of prevalent pollutants, which include two metals and, as a more realistic sample, a leachate from smoked cigarette filters. All three pollutants were tested at sublethal concentrations. This method provides an efficient approach to assess the toxicity of chemicals and water quality. Full article

Boron serves as a necessary micronutrient, but elevated concentrations may exert toxic effects, which has raised concern over its increasing presence in the environment owing to anthropogenic activities. This study assessed the sublethal effects of boron on Daphnia magna, which is a commonly employed model species in freshwater ecotoxicology. D. magna neonates were subjected to boron concentrations ranging from 0.5 to 350 mg B/L over 48 h, and acute toxicity (EC₅₀), along with swimming velocity, heart rate, and oxidative stress responses, were evaluated as toxicological endpoints. Swimming velocity increased significantly at 80 mg B/L before declining, while heart rate significantly decreased at 250 mg B/L (p < 0.05). In addition, significant increases in oxidative stress responses were observed at sublethal concentrations of 40 and 80 mg B/L (p < 0.05), highlighting the sensitivity of oxidative stress responses to boron exposure. These findings demonstrate the previously underexplored sublethal effects of boron on D. magna, including alterations in swimming velocity, heart rate, and antioxidant defenses, emphasizing the need for integrated endpoints in ecotoxicological assessments. Full article

Tetracyclines (TCs) are antibiotics widely used in human and veterinary medicine as well as in agricultural practices. They may be retained in soil or drift into freshwater, thereby exerting effects on non-target organisms and deteriorating ecological quality. In this study, tetracycline (T), oxytetracycline (OT), chlortetracycline (CT), and their binary and ternary mixtures were evaluated using a battery of bioassays including terrestrial plants, aquatic crustaceans, a ciliate protist and a bacterial species. Results showed a concentration-dependent effect for parameter immobilization in Daphnia magna and Artemia salina, seed germination in the terrestrial plants, and bioluminescence inhibition and growth inhibition in Aliivibrio fischeri and Tetrahymena thermophila, respectively. For A. fischeri, statistically significant interactions were observed between dose and exposure time. A. salina demonstrated greater sensitivity than D. magna in all cases. Both A. salina and A. fischeri showed increased toxicity to OT and the ternary mixture. Dicots presented greater sensitivity than the monocot species in all cases. In the combined exposures, there was a deviation from the concentration addition (CA) model, with possible synergism for CT + T and the ternary mixture for A. fischeri. The concurrent environmental exposure of non-target organisms to TCs should be investigated further. Full article

Research on the river-groundwater cross-contamination of per- and polyfluoroalkyl substances (PFAS) in karst regions is limited. We therefore investigated the PFAS occurrence, spatial distribution, sources and ecological risks in the Lijiang River basin, a typical karst area. PFAS concentrations were relatively low (0.08–74.0 ng/L, mean 4.13 ng/L). PFBA, PFHxA, PFNA and 6:2 FTS were widely detected. Short-chain PFAS concentrations (0.08–74.0, mean 4.75 ng/L) were higher than long-chain ones (0.02–3.31, mean 0.72 ng/L). Unusually, groundwater PFAS concentrations (0.08–74.0, mean 7.97 ng/L) exceeded those in rivers (0.08–11.7, mean 2.31 ng/L). Positive matrix factorization (PMF) combined with spatial distribution identified five main sources: sewage treatment plants (24.0%), gas station leaks/wastewater discharges (21.3%), untreated domestic sewage (18.1%), small-scale industrial wastewater (16.7%), and agricultural/aquaculture wastewater (20.2%). The ecological risk assessment showed that, except for PFUnDA posing a low risk to algae, the other PFASs presented no significant risk to algae, daphnia or fish. The human health risk assessment indicated minimal direct health risks. Our findings indicate that some PFASs in groundwater and river water may share common sources, highlighting the complex PFAS migration between rivers and groundwater in karst regions. Full article

The Directive (EU) 2024/3019 on urban wastewater treatment (WWT) imposes new, stringent targets for nutrients and pharmaceutical compounds, thereby requiring the implementation of tertiary and quaternary treatments and promoting water reuse. This study evaluated the ecotoxicological impacts of advanced wastewater treatments applied to the effluent from a WWTP after secondary treatment: ultrafiltration (UF), ultraviolet radiation (UV), ozonation (OZ), and non-thermal plasma (NTP). Ecotoxicity assays were conducted using Raphidocelis subcapitata (chronic tests) and Daphnia magna (acute and chronic tests), representing primary producers and consumers, respectively. For R. subcapitata, no significant growth inhibition was observed for most treatments, while growth was promoted due to the presence of nutrients, except for OZ, which produced inhibitory effects. In D. magna, acute toxicity was low for most treatments, except for OZ, which showed significant toxicity. An additional chronic exposure experiment was conducted for the NTP-treated effluent, inducing adverse effects on growth and reproduction of D. magna; in contrast, R. subcapitata showed no effects, demonstrating species-specific sensitivity and trophic-level-dependent responses. These findings demonstrate that although advanced oxidation technologies enhance water quality, they may cause sublethal and lethal ecotoxicity effects, highlighting the importance of ecotoxicological evaluations in risk assessment of quaternary treatments, framed by Directive (EU) 2024/3019. Full article

Phytoremediation is a sustainable approach for the remediation of heavy metal–contaminated soils; however, the management of contaminated biomass generated during this process remains an insufficiently addressed challenge. Such biomass constitutes a secondary waste stream that may release mobile pollutants and pose environmental risks. In this study, an integrated ecotoxicological assessment framework was applied to evaluate phytoremediation-derived biomass and its transformation products obtained via pyrolysis. Two types of woody biomass with different heavy metal contents and their corresponding biochars produced at 700 °C were investigated. A multitrophic battery of bioassays combining direct exposure assays using terrestrial organisms (higher plants, Eisenia fetida, and soil microbial activity) with leachate-based assays using aquatic organisms (Lemna minor, Daphnia magna, and Aliivibrio fischeri) was applied. Untreated biomass exhibited high to extreme toxicity in aquatic systems (toxic units, TU >100) and significant phytotoxic effects. Pyrolysis substantially reduced contaminant mobility and ecotoxicity of leachates, resulting in lower toxicity (TU typically <15) and no significant effects on plant growth, earthworm survival, or soil microbial functional diversity. Residual toxicity was linked to elevated pH and trace amounts of thermally generated organic substances. These results demonstrate that pyrolysis effectively reduces the environmental risk of contaminated biomass and supports the use of multitrophic ecotoxicological testing for safe waste valorization within circular economy strategies. Full article

Nutrient-rich inputs into surface waters can promote harmful blooms of Prymnesium parvum by stimulating growth under favorable environmental conditions. Glyphosate can enter aquatic ecosystems and affect algal growth, potentially further influencing P. parvum blooms. The interaction effects of nutrient conditions and glyphosate on P. parvum toxicity, however, remain unknown. This study determined the effects of glyphosate on the growth and toxicity of P. parvum. Cultures were exposed to glyphosate (0, 0.1, 0.25, and 0.5 mg L⁻¹) under phosphorous (P)-sufficient (f/2 medium) and P-limited conditions (phosphate-free medium) and, for the 0.1 mg L⁻¹ cultures, P. parvum toxicity (10,000 cells mL⁻¹) to Daphnia pulex was assessed. The addition of 0.1 and 0.25 mg glyphosate L⁻¹ significantly stimulated P. parvum growth in P-sufficient conditions, resulting in the highest growth rates and final cell densities. In P-limited conditions, however, glyphosate had no effect. P-sufficient cultures with 0.1 mg glyphosate L⁻¹ exhibited higher toxicity compared to controls. Although toxicity under P limitation was consistently higher than under P sufficiency, glyphosate did not affect this toxicity. These results suggest that glyphosate, at environmentally relevant concentrations, stimulates the growth and toxicity of P. parvum under nutrient-sufficient but not nutrient-limited conditions. Full article

This study addresses the growing need for efficient and reliable application of New Approach Methodologies (NAMs) to assess aquatic toxicity of chemicals in response to increasing environmental contamination and regulatory demands. Particular emphasis is placed on in silico methods, especially quantitative structure–activity relationship (QSAR) modeling. Curated and structurally diverse datasets were compiled for representative aquatic organisms from different trophic levels, including the microalga Raphidocelis subcapitata, the crustacean Daphnia magna, and fish species (zebrafish embryo and fathead minnow). The models demonstrated consistently strong predictive performance across the evaluated assays. They were based on interpretable molecular descriptors associated with lipophilicity, polarity, and molecular reactivity. Furthermore, interspecies quantitative structure–activity–activity relationship (QSAAR) models were developed, demonstrating that toxicity data from lower trophic levels, combined with structural descriptors, can effectively predict fish toxicity. These models support cross-species extrapolation and contribute to environmental hazard assessment and regulatory decision-making. Full article

Glitter is a distinctive and largely overlooked form of primary microplastic. Unlike more commonly studied microplastics, glitter particles are typically flat, highly reflective, multi-layered, and are composed of polymers such as polyethylene terephthalate, polyvinyl chloride with metallic coatings and a wide range of additives. In response to regulatory restrictions on intentionally added microplastics and increasing consumer demand, “eco-friendly” alternatives based on modified regenerated cellulose, cellulose nanocrystals, or mica have been introduced, although their environmental safety remains insufficiently characterized. This review synthesizes current knowledge on the environmental occurrence and ecotoxicological effects of both conventional and biodegradable glitters. A systematic literature search in Scopus identified 15 peer-reviewed experimental studies meeting predefined inclusion criteria. Evidence spans a wide range of taxa, including bacteria (i.e., Aliivibrio fischeri), microalgae and cyanobacteria (i.e., Phaeodactylum tricornutum, Raphidocelis subcapitata, Microcystis aeruginosa), aquatic plants (i.e., Lemna minor, Egeria densa), marine and freshwater invertebrates as crustaceans (i.e., Daphnia magna), bivalves (i.e., Mytilus galloprovincialis), sea urchins (i.e., Paracentrotus lividus), brine shrimp (Artemia sp.) and terrestrial soil fauna (Eisenia fetida, Folsomia candida). Results indicate that glitter cannot be treated as a uniform stressor: biological responses vary markedly with particle size, shape, colour, polymer type, additive composition, and weathering time, and leachates often exert stronger effects than intact particles. Reported impacts include impaired photosynthesis and growth, oxidative stress, developmental abnormalities, altered energy metabolism, and reduced reproduction. Substantial gaps remain regarding environmental concentrations, ageing processes, mixture effects, and long-term ecological consequences, particularly for biodegradable glitters. Addressing these gaps will require realistic exposure scenarios, mesocosm and field studies, and integrated chemical–biological approaches to support robust risk assessment and safer material design. Full article

Microplastic pollution is a pervasive and ecologically significant threat to aquatic systems. Zooplankton, as key mediators of energy transfer and carbon cycling, are particularly vulnerable to microplastic ingestion due to size overlap with natural prey. This systematic literature review synthesises 250 peer-reviewed studies on zooplankton–microplastic and nanoplastic interactions, identified through a Web of Science search (403 initial records, 2012–2026) and screened using Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria. Bibliometric and narrative thematic analyses were conducted to evaluate publication trends, taxonomic coverage, biological endpoints, experimental design, particle characteristics, and geographic distribution. Publication output increased rapidly after 2019, with nanoplastics emerging as a major research focus. The literature is strongly biassed toward model organisms such as Daphnia magna and Artemia salina, with limited representation of marine taxa. Ingestion and oxidative stress are the most studied endpoints, while trophic transfer, carbon flux, and multi-stressor interactions remain underexplored. Reported experimental designs are predominantly laboratory-based and frequently employ supra-environmental concentrations and simplified particle types. A major geographic gap is identified for the Black Sea, with minimal coverage and no data for dominant regional species. Future research should prioritise ecologically realistic conditions, broader taxonomic and geographic representation, and integrated multi-stressor approaches to support ecosystem-based management. This review characterises publication patterns and knowledge gaps; it does not constitute a formal evidence synthesis, and frequency distributions reflect research coverage rather than strength of evidence. Full article

Mercury contamination in water poses severe environmental and health risks, requiring efficient and sustainable removal strategies. In this study, rice husk (RH), rice husk-derived materials, including rice ash (RHA), and Mobil Composition of Matter No. 41 (MCM-41) were evaluated as adsorbents for Hg(II) removal in aqueous systems. Among the tested materials, MCM-41 exhibited superior adsorption performance, achieving up to 98% Hg(II) removal under optimal conditions (pH 6.8, 3 g L⁻¹ of adsorbent, and a pollutant concentration of 0.90 mg L⁻¹). Adsorption followed a pseudo-second-order kinetic model and was best described by the Langmuir isotherm, indicating monolayer adsorption. The maximum adsorption capacity reached 0.80 mg g⁻¹. Thermodynamic analysis revealed that the process was spontaneous and exothermic, primarily governed by coordination interactions and hydrogen bonding with surface silanol groups. The adsorbent’s applicability was further assessed in distilled water, synthetic industrial wastewater, and river water. Although high removal efficiencies were maintained, a decrease was observed in complex matrices due to competition from coexisting ions. Reusability tests demonstrated that MCM-41 retained its performance over four adsorption cycles. Environmental safety was evaluated through ecotoxicological and microbiological assays. Daphnia magna exhibited high sensitivity to Hg(II) (EC₅₀ values of 0.0220 mg L⁻¹ at 24 h and 0.0158 mg L⁻¹ at 48 h), while treated samples showed improved germination indices of Lactuca sativa, particularly in distilled and river water. However, residual toxicity persisted in industrial wastewater matrices. Overall, rice husk-derived MCM-41 is a promising and sustainable adsorbent for Hg(II) removal, though further optimization is needed to mitigate residual toxicity in complex water matrices. Full article

Sediment-derived turbidity, intensified by anthropogenic activities, is a widespread form of particulate pollution in aquatic ecosystems. Yet, its effects on planktonic crustaceans remain insufficiently quantified across particle types and disturbance regimes. We exposed five species (Daphnia magna, Leptodora kindtii, Eurytemora velox, Thermocyclops crassus, and T. oithonoides) to turbidity generated by red clay, diatomaceous earth (amorphous silica), and bentonite at three substrate loads (0.5, 1.5, and 3 g/100 mL) and three resuspension regimes (1, 12, and 24 disturbances per day) for 72 h. Particle size distributions and turbidity reduction under free sedimentation were measured using NTU and FAU. Survival decreased across all species, with substrate load as the most consistent predictor, while disturbance frequency showed taxon-dependent effects, particularly in D. magna and L. kindtii. Sensitivity differed among taxa, with L. kindtii and E. velox being the least tolerant, whereas cyclopoid copepods (Thermocyclops spp.) were comparatively resistant. Substrate identity also affected responses, with D. magna being particularly sensitive to amorphous silica relative to clay and bentonite. These findings indicate that survival under sediment-derived turbidity depends on both particle properties and exposure regime, suggesting that increasing sediment mobilization may act as an ecological filter shaping plankton communities. Full article

Trans-cinnamaldehyde (CIN), the main component of cinnamon essential oil, is a promising sustainable alternative to synthetic pesticides. Despite its use, ecotoxicological data on non-target species remain fragmented. This study systematically evaluates CIN’s acute toxicity across multiple trophic levels to characterize the biological sensitivity and environmental response of key organisms. Aquatic assays measured bioluminescence inhibition in Aliivibrio fischeri and immobilization in Daphnia magna. Terrestrial evaluations included lethality tests on Eisenia fetida and root elongation in Allium cepa. Additionally, the impact on soil and river microbial communities was analyzed via Biolog EcoPlates™. Significant dose–response relationships were observed across all bioindicators (p < 0.0001). A. fischeri was the most sensitive species (EC₅₀ = 1.428 mg·L⁻¹), followed by D. magna (EC₅₀ = 4.533 mg·L⁻¹). In terrestrial models, A. cepa (EC₅₀ = 11.644 mg·L⁻¹) exhibited higher sensitivity than E. fetida (LC₅₀ = 412.519 mg·kg⁻¹). Microbial metabolic activity showed dose-dependent inhibition, particularly affecting carbohydrate and polymer degradation at high concentrations. These findings define the first ecotoxicological benchmarks for CIN, establishing EC₁₀ and EC₅₀ values under standardized conditions. These data provide the necessary toxicological constraints to ensure environmental safety in future field-scale applications of this natural compound. Full article