Aquatic Organisms Research Articles (Page 1)

Octamethylcyclotetrasiloxane (D4) is a cyclic volatile methylsiloxane compound associated with the production of polydimethylsiloxanes (PDMS). Depending on processing conditions, silicone fluids made by equilibration polymerization can contain residual D4 at parts-per-million to parts-per-hundred levels. When silicone fluids enter the environment through use or disposal, aquatic organisms may be exposed to residual D4. To accurately assess the contribution of D4 to the aquatic hazard of silicone fluids, knowledge of the partitioning behavior of D4 is needed. In this study, PDMS-to-air partition coefficients (K PDMS-air) for D4 were directly measured at 21 °C using a static equilibration method. The influence of various factors on K PDMS-air was explored, including the PDMS fluid viscosity (molecular weight), the D4 concentration in the polymer, addition of hydrophobized fumed silica to PDMS, and the presence of amine functional groups within the PDMS structure. For permethylated PDMS, log K PDMS-air values varied between 4.39 and 4.53. Incorporation of treated silica filler at up to 25%w/w had no impact on K PDMS-air, while introduction of (aminopropyl)methyl-dimethylsiloxy units to the polymer (3.7 wt% nitrogen) produced modestly lower log K PDMS-air, 4.19. The K PDMS-air values were combined with reported air-water partition coefficients (K air-water) for D4 to calculate values of K PDMS-water based on the thermodynamic cycle. The resulting log K PDMS-water values ranged from 6.88 to 7.22, which were used to estimate the maximum attainable aqueous D4 concentrations for different polymer/water phase ratios. For a D4 content of 0.025% w/w in the polymer, the current threshold for classification of the polymer as hazardous to the aquatic environment, the maximum aqueous D4 concentration was ≤ 0.032 μg/L. These concentrations were at least 100-fold less than chronic aquatic toxicity thresholds derived from studies with D4, suggesting that the 0.025% w/w threshold is overly stringent in assigning aquatic hazard classifications to PDMS materials like those tested here.

Introduction The dinoflagellate genus Karenia G. Hansen and Moestrup is notorious for forming harmful algal blooms (HABs), most of which can produce a variety of potent toxins (e.g., brevetoxins), killing fish and other aquatic animals above a certain cell density. Among the 11 currently accepted Karenia species, more than half of which are toxic, 8 species ( K. bicuneiformis , K. brevis , K. brevisulcata , K. hui, K. longicanalis, K. mikimotoi, K. papilionacea , and K. selliformis ) have been reported or described in Chinese coastal waters. Among these, K. papilionacea is globally distributed, with records in Asia, Europe, America, and Oceania. In China, it occurs in the East and South China Seas, though its morphological characterization and toxicology have not been well documented. Methods In this study, we established a clonal culture of Karenia papilionacea through single-cell isolation from the coast of Qingdao (belonging to the Yellow Sea), China, and characterized its morphology using light microscopy (LM) and scanning electron microscopy (SEM), as well as its phylogeny based on large subunit (LSU) rDNA sequences. More importantly, we characterized the impact of K. papilionacea culture on brine shrimp egg hatching, as well as its toxicity to marine animals (rotifers, brine shrimp, and finfish) using laboratory bioassays. Results We observed the typical diagnostic features of K. papilionacea . In phylogenetic trees inferred using Bayesian inference (BI) and maximum likelihood (ML) techniques, the Yellow Sea strain branched together with other entities of K. papilionacea , but formed a new group, which is different from other strains reported in the East and South China Seas. The genetic distances among our strain of K. papilionacea and other isolates ranged from 0.002 to 0.011, corresponding to 6–23 base differences. The Yellow Sea strain exhibited significant lethal effects on rotifer, brine shrimp, and finfish, but had a minor impact on the hatching success of brine shrimp eggs. Discussion This study reports K. papilionacea in northern China for the first time, expanding the known distribution range of this toxic HAB-forming species along the Chinese coast. Our findings establish a foundation for monitoring and risk assessment of K. papilionacea in Chinese coastal waters and advance fundamental ecological knowledge of this toxic species. Future studies are needed to characterize toxins produced by geographical strains of K. papilionacea .

Silicon dioxide nanoparticles (SiO2NPs) are widely used in various industries, raising concerns about their potential toxicity in aquatic organisms. Although several studies have investigated the general toxic effects of SiO2NPs, little is known about their impact on the nervous system and behavior of aquatic vertebrates. Furthermore, the combined assessment of behavioral, histological, and biochemical responses remains scarce. The study aimed to evaluate the effects of SiO2NPs on behavioral, histological, and biochemical parameters in adult zebrafish (Danio rerio). Fish were exposed to sublethal concentrations of SiO2NPs and their behavior was assessed using the social interaction test and the color preference test. Significant alterations in social behavior, such as reduced group cohesion and increased isolation tendencies, were observed. Additionally, exposed zebrafish exhibited a marked shift in color preference, indicating potential disruptions in sensory or cognitive function. Histological analyses revealed dose dependent tissue changes in brain structures, while biochemical assays indicated reduced activity of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), suggesting elevated oxidative stress (OS). To the best of our knowledge, this is one of the first studies to integrate behavioral, histological, and biochemical endpoints in zebrafish to assess the neurotoxic potential of SiO2NPs. These findings suggest that SiO2NPs can induce histological alterations in brain structures, neurobehavioral changes, and OS in zebrafish, underscoring the novelty and relevance of this interdisciplinary approach, and the importance of further studies on SiO2NPs environmental and health impacts.

ABSTRACT The nanoconfined carbon materials has attracted wide attention from academia and industry because they can disperse and stabilize metal nanoparticles through spatial confinement, preventing them from agglomerating and improving their stability and catalytic activity. Herein, in situ encapsulation of Co‐N/C nanocatalyst into carbon nanocubes (Co–CNs) was designed and reported for selectively catalytic degradation of sulfadiazine via peroxodisulfate (PDS) activation. This structure of Co–CN‐800 played a vital role in intercepting natural organic matters and access of target contamination for achieving selective degradation of target contamination. The electron paramagnetic resonance result and quenching experiments confirmed that O 2 • − and 1 O 2 are the primary reactive oxygen species in the Co–CN‐800/PDS system. The specific parameters (such as E HOMO and ionization potential) of organic pollutants were found to be highly relevant to the ln k obs values of the removal of organic pollutants by Co–CN‐800/PDS system. This suggested that the occurrence of electron transfer between PDS and pollutants, which was verified by electrochemical analysis, seemed to play a crucial role in their degradation kinetics in Co–CN‐800/PDS system. Seed germination test and ecological structure–activity relationship model had confirmed the bio‐toxicity of SDZ to aquatic organism and wheat seeds was strongly decreased to ecological environment safety standards after treatment by Co–CN‐800/PDS system. For the real wastewater, the total organic carbon and chemical oxygen demand of raw pig effluent decreased by 21.4 resp . 30.4%, after treatment by Co–CN‐800/PDS system in 60 min.

Aquatic ecosystems are increasingly contaminated by complex mixtures of perfluoroalkyl and polyfluoroalkyl substances (PFAS) and pesticides, yet the combined toxicological impacts of these pollutants on aquatic organisms remain poorly understood. This study investigated the effects of chlorpyrifos (CPF) (0.62-620 μg/L) and perfluorohexanoic acid (PFHxA) (10 μg/L) in their isolated forms and as a mixture on developing zebrafish (Danio rerio). We measured several endpoints related to survivability, hatchability, malformations, apoptosis, reactive oxygen species (ROS), locomotor activity, and gene expression following a 7-day exposure. We also employed a computational approach to identify molecular interactions between CPF and PFHxA. Survival decreased with exposure to CPF and the mixture CPF/PFHxA at 620 μg/L. Increased deformity rates were observed at 62 μg/L CPF, but no effects were observed in the hatching rate. In the behavior assay, CPF and the mixture decreased the larvae's locomotor activity. Expression of genes related to neurotoxicity and oxidative stress was altered mainly in the coexposure group. ROS levels were higher in the 62 μg/L CPF than in the solvent control but lower in the coexposure with 0.62 μg/L CPF/PFHxA. Our results demonstrate interactive effects of PFHxA and chlorpyrifos, emphasizing the importance of mixture toxicity in aquatic risk assessment.

Imidacloprid (IMI), a neonicotinoid insecticide, is widely recognized for its environmental persistence and toxicity to non-target aquatic organisms. Extended photoperiod exposure (EPE), an emerging anthropogenic stressor, further disrupts aquatic ecosystems by altering physiological and biological processes. However, their combined impacts on aquatic species remain insufficiently explored. This study evaluates the synergistic effects of IMI and EPE on Procambarus clarkii, an ecologically and economically significant crayfish species. Crayfish were exposed to 25 µg/L IMI under normal photoperiod (1000 lx, L:D = 12:12 h) and additional intensified and extended photoperiod (5000 lx, L:D = 18:6 h) treatments over one month. Key parameters, including survival rate, growth performance, oxidative stress markers, immune enzyme activities, neuroendocrine hormone levels, and gene expression, were assessed. The results indicate that EPE significantly amplifies the adverse effects of IMI. EPE reduced survival rates and growth performance, particularly in the 5000 lx group. IMI combined with EPE markedly elevated oxidative stress, as evidenced by increased malondialdehyde (MDA) levels and altered activities of superoxide dismutase (SOD) and catalase (CAT). Immune functions were impaired, with significant reductions in lysozyme (LZM) and acid phosphatase (ACP). Neuroendocrine disruption was observed through suppressed melatonin (MT) levels under EPE. Gene-expression analysis revealed upregulation of oxidative stress and apoptotic pathways (Cu/Zn-SOD, CAT and caspase-3) and downregulation of anti-apoptotic genes (bcl-2) and molt-inhibiting hormone (MIH). This study demonstrates that EPE exacerbates IMI-induced physiological and biochemical disruptions in P. clarkii. The findings highlight the pressing need for integrated management strategies addressing chemical and light pollution to protect aquatic ecosystems and sustain economically important species like crayfish.

The operational phase of offshore wind farms, lasting up to 20–25 years, exceeds the construction phase in duration. The ecological effects of underwater noise demand serious consideration, necessitating urgent research into its acoustic characteristics. This review conducts a systematic analysis of measurements of underwater noise from operational offshore wind farms, considering the correlations between turbine noise and distance, wind speed, turbine power, and foundation type. Propagation distance is the most critical factor influencing the underwater sound pressure level (SPL) of wind turbines, exhibiting a negative correlation with the SPL, with an attenuation of approximately 20.4 dB/decade. In contrast, wind speed and turbine power show a positive correlation with the SPL, with increase rates of 18.5 dB/decade and 12.4 dB/decade, respectively. Further analysis shows that foundation type and drive technology also have a significant impact on underwater SPL. With technological innovation, specifically the upgrade from conventional geared drive to direct-drive technology, the level of underwater noise can be reduced by approximately 9 dB, with the primary peak frequency being shifted to a lower range. Moreover, significant variations in SPLs were noted with the utilization of various types of foundation structures, with monopile foundations exhibiting the highest SPLs of underwater noise. These conclusions have important reference value for the scientific assessment of the health of aquatic organisms and ecosystems.

Heavy metal pollution in marine ecosystems poses significant threats to aquatic organisms and human health. This study determined the concentrations of metals in the edible muscle tissues of recently obtained Mullus surmuletus samples collected from three distinct regions of the Mersin Bay, Northeastern (NE) Mediterranean Sea. The muscle tissues of the obtained fish samples were analyzed for the selected metals using microwave-assisted digestion and the ICP-MS technique. Then, potential health risks were assessed using Target Hazard Quotient (THQ) and Cancer Risk (CR) values. Study findings showed that the mean metal concentrations varied between 1.58 and 9.75mg/kg for Al, 0.0018-0.0020mg/kg for Cr, 0.292-0.680mg/kg for Mn, 6.20-20.05mg/kg for Fe, 0.0006-0.0016mg/kg for Co, 0.0007-0.0039mg/kg for Ni, 0.450-0.562mg/kg for Cu, 4.651-5.823mg/kg for Zn, 0.00019-0.00022mg/kg for Cd, and 0.0019-0.0030mg/kg for Pb, respectively. Metal concentrations varied significantly among sampling locations, with the highest levels detected in the central and eastern regions of the bay, highly influenced by riverine inputs from the Seyhan and Berdan Rivers, as well as maritime and wastewater discharges. One-way ANOVA and Pearson correlation analyses indicated significant spatial variation and potential common sources of metal contamination in the study region. Though all metal concentrations in fish samples were below national and international permissible threshold limits for human consumption, health risk assessments indicated that copper may pose long-term carcinogenic risks.

Ammonia nitrogen is a ubiquitous environmental stressor in aquaculture systems, posing severe toxicity to aquatic organisms. This study investigated the histopathological and physiological responses of Tachysurus fulvidraco gills under acute ammonia stress. We exposed fish to gradient concentrations of ammonia nitrogen and analyzed gill tissue histology, serum ion concentrations, blood ammonia levels, and inflammatory markers. Results showed a 96h LC50 of 28.12 mg/L. Histopathological analysis revealed severe gill damage, including lamellar fusion, epithelial necrosis, and inflammatory cell infiltration, linked to NF-κB-mediated upregulation of inflammatory factors and altered expression of tight junction proteins (occludin, ZO-2). Concurrently, serum Na⁺ and K⁺ levels significantly decreased, while blood ammonia rose dose-dependently. These findings demonstrate that acute ammonia stress disrupts gill structural integrity and osmoregulatory function through inflammation and barrier dysfunction, highlighting its role in ammonia toxicity mechanisms and providing insights for aquaculture health management.

This comprehensive review compiles current knowledge about the connection between plastic waste and the selection and transmission of antibiotic resistance genes (ARGs) in aquatic ecosystems, which can result in ARG contamination of fishery products—a significant source of microplastic (MP) introduction into the food chain. Plastic debris in aquatic environments is covered by a biofilm (the plastisphere) in which antibiotic-resistant bacteria (ARB) are selected and horizontal gene transfer (HGT) of ARGs is facilitated. The types of plastic waste considered in this study for their role in ARG enrichment are mainly microplastics (MPs), and also nanoplastics (NPs) and macroplastics. Studies regarding freshwaters, seawaters, aquaculture farms, and ARG accumulation favored by MPs in aquatic animals were considered. Most studies focused on the identification of the microbiota and its correlation with ARGs in plastic biofilms, while a few evaluated the effect of MPs on ARG selection in aquatic animals. A higher abundance of ARGs in the plastisphere than in the surrounding water or natural solid substrates such as sand, rocks, and wood was repeatedly reported. Studies regarding aquatic animals showed that MPs alone, or in association with antibiotics, favored the increase in ARGs in exposed organisms, with the risk of their introduction into the food chain. Therefore, reducing plastic pollution in water bodies and aquaculture waters could mitigate the ARG threat. Further investigations focused on ARG selection in aquatic animals should be conducted to better assess health risks and increase awareness of this ARG transmission route, enabling the adoption of appropriate countermeasures.

Ciliate infestations in aquatic organisms are commonly associated with aquaculture, yet their impact on natural ecosystems remains largely understudied. This study describes a mobilid peritrich species infesting the gills of Octopus bimaculatus from the Gulf of California, Mexico. All 76 examined hosts (100%) exhibited infestation, with a mean intensity of 687 ± 228 (279–1077) urceolariid cells per gill. The ciliate cells displayed morphological traits consistent with those of the genus Urceolaria: turban-shaped cells measuring 44.2 ± 13.2 (31.3–88.6) µm in diameter; an adhesive disc of 36.5 ± 10.7 (29.2–74.6) μm in diameter; 18–19 plates measuring 11.0 ± 0.86 (9–12) µm in length; and 166–169 radial pins. Phylogenetic analysis of 18S rDNA sequences placed this species within the genus Urceolaria, a sister group to Urceolaria urechi and Urceolaria serpularum, with a genetic distance of 1.0% with respect to the previously described species. Combined morphological and molecular data support the description of a new species, Urceolaria carmenae n. sp. This is the first record of a mobilid peritrich in cephalopod mollusks, thereby enhancing our understanding of the diversity of ciliates among marine invertebrates in their natural habitats.

Endocrine-disrupting chemicals (EDCs) are widespread contaminants that interfere with hormonal signaling and compromise reproductive success in aquatic organisms. Vitellogenin (VTG) is one of the most widely established biomarkers of estrogenic exposure, especially in males and juveniles. However, evidence from multi-omics studies indicates that VTG induction occurs within broader transcriptional and regulatory networks, involving genes such as cyp19a1 (aromatase), cyp1a (cytochrome P4501A), and other stress-responsive genes, underscoring the complexity of endocrine disruption. This review focuses on nuclear receptor isoforms, including estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and androgen receptor (AR) variants. We examine the diversification of vtg gene repertoires across teleost genomes and epigenetic mechanisms, such as DNA methylation and microRNAs, that modulate sex-dependent sensitivity. In addition, we discuss integrative approaches that combine VTG with transcriptomic, epigenetic, and histological endpoints. Within the Adverse Outcome Pathway (AOP) and weight-of-evidence (WoE) frameworks, these strategies provide mechanistic links between receptor activation and reproductive impairment. Finally, we outline future directions, focusing on the development of sex-specific biomarker panels, the integration of omics-based data with machine learning, and advances in ecogenomics. Embedding molecular responses into ecological and regulatory contexts will help bridge mechanistic insights with environmental relevance and support sustainability goals such as SDG 14 (Life Below Water).

Competitive blockade of NKCC1 by potassium suppresses thallium bioaccumulation and neurotoxicity in zebrafish: Implications for aquatic toxicity.

Quantitative analysis of neurotransmitters in fish brain: A tool to assess neurochemical effects of psychoactive pollutants.

Reactive oxygen species (ROS)-mediated photodegradation mechanism of 2,4'-DDT in the irradiated Pearl River suspended particulate matter-water system.

Fungal chitosan in focus: a comprehensive review on extraction methods and applications.

Microplastics in aquatic communities of neotropical agroecosystems.

An environmentally friendly cucurbit[7]uril-mediated magnetic-assisted matrix solid-phase dispersion extraction combined with HPLC-MS/MS for multiple analysis of pharmaceuticals and personal care products in aquatic organisms

Acute toxicity effects of rice paddy bactericide bismerthiazol on zebrafish (Danio rerio) embryos.

A DFT study on degradation of aflatoxin B1 using some reactive oxygen and nitrogen species of plasma-activated water.