Metabolomics perspectives of the ecotoxicological risks of polycyclic aromatic hydrocarbons: A scoping review.

Polycyclic Aromatic Hydrocarbons (PAHs) represent persistent environmental pollutants ubiquitously distributed in the environment. Their presence alongside various other contaminants gives rise to intricate interactions, culminating in profound deleterious consequences. The combination effects of different PAH mixtures on biota remains a relatively unexplored domain. Recent studies have harnessed the exceptional sensitivity of metabolomic techniques to unveil the significant ecotoxicological perils of PAH pollution confronting both human populations and ecosystems. This article furnishes a comprehensive overview of current literature focused on the metabolic repercussions stemming from exposure to complex mixtures of PAHs or PAH-pollution sources using metabolomics approaches. These insights are obtained through a wide range of models, including in vitro assessments, animal studies, investigations on human subjects, botanical specimens, and soil environments. The findings underscore that PAH mixtures induce cellular stress responses and systemic effects, leading to metabolic dysregulations in amino acids, carbohydrates, lipids, and other key metabolites (e.g., organic acids, purines), with specific variations observed based on the organism and PAH compounds involved. Additionally, the ecological consequences of PAH pollutants on plant and soil microbial responses are emphasized, revealing significant changes in stress-related metabolites and nutrient cycling in soil ecosystems. The complex interplay of various PAHs and their metabolic effects on several models, as elucidated through metabolomics, highlight the urgency of further research and the need for comprehensive strategies to mitigate the risks posed by these widespread environmental pollutants.

Challenges and opportunities in sustainable management of microplastics and nanoplastics in the environment.

The accumulation of microplastics (MPs) and nanoplastics (NPs) in terrestrial and aquatic ecosystems has raised concerns because of their adverse effects on ecosystem functions and human health. Plastic waste management has become a universal problem in recent years. Hence, sustainable plastic waste management techniques are vital for achieving the United Nations Sustainable Development Goals. Although many reviews have focused on the occurrence and impact of micro- and nanoplastics (MNPs), there has been limited focus on the management of MNPs. This review first summarizes the ecotoxicological impacts of plastic waste sources and issues related to the sustainable management of MNPs in the environment. This paper then critically evaluates possible approaches for incorporating plastics into the circular economy in order to cope with the problem of plastics. Pollution associated with MNPs can be tackled through source reduction, incorporation of plastics into the circular economy, and suitable waste management. Appropriate infrastructure development, waste valorization, and economically sound plastic waste management techniques and viable alternatives are essential for reducing MNPs in the environment. Policymakers must pay more attention to this critical issue and implement appropriate environmental regulations to achieve environmental sustainability.

Specific toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata.

Pharmaceuticals are produced to inflict a specific physiological response in organisms. However, as only partially metabolized after administration, these types of compounds can also originate harmful side effects to non-target organisms. Additionally, there is still a lack of knowledge on the toxicological effects of legacy pharmaceuticals such as the antibiotic azithromycin. This macrolide occurs at high concentrations in the aquatic environment and can constitute a threat to aquatic organisms that are at the basis of the aquatic food chain, namely microalgae. This study established a high-throughput methodology to study the toxicity of azithromycin to the freshwater microalga Raphidocelis subcapitata. Flow cytometry and pulse amplitude modulated (PAM) fluorometry were used as screening tools. General toxicity was shown by effects in growth rate, cell size, cell complexity, cell viability and cell cycle. More specific outcomes were indicated by the analysis of mitochondrial and cytoplasmatic membrane potentials, DNA content, formation of ROS and LPO, natural pigments content and photosystem II performance. The specific mode of action (MoA) of azithromycin to crucial components of microalgae cells was revealed. Azithromycin had a negative impact on the regulation of energy dissipation at the PSII centers, along with an insufficient protection by the regulatory mechanisms leading to photodamage. The blockage of photosynthetic electrons led to ROS formation and consequent oxidative damage, affecting membranes and DNA. Overall, the used methodology exhibited its high potential for detecting the toxic MoA of compounds in microalgae and should be considered for future risk assessment of pharmaceuticals.

Bioavailability and toxicity of microplastics to fish species: A review.

The prevalence of microplastics in aquatic environments has raised concerns about their availability and risks to aquatic biota. Since fish is an important source of animal protein for human beings, the occurrence and potential impacts of microplastics in fishes deserve special attention. Although there have been an increasing number of studies concerning microplastics ingestion and effects in fish, review papers specifically focusing on this issue are few. This review summarized the current knowledge about the bioavailability and toxicity of microplastics to fish species. By collating literatures, it can be concluded that microplastics contamination could occur in almost all types of aquatic habitats around the globe. Both field and laboratory studies suggest that fishes are very susceptible to microplastics ingestion. Compared with marine species, freshwater fishes have been less studied. Microplastics alone or in combination with other contaminants could cause various health problems to fish after exposure. There still exist some debates over the environmental relevance of the laboratory-based effect studies and the relative contribution of microplastics in increasing the exposure of fish to hazardous chemicals. Hopefully, this review could extend the current knowledge on the ecotoxicological impacts of microplastics contamination to fish and provide guidance for future research.

Engineered nanomaterials: From their properties and applications, to their toxicity towards marine bivalves in a changing environment.

As a consequence of their unique characteristics, the use of Engineered Nanomaterials (ENMs) is rapidly increasing in industrial, agricultural products, as well as in environmental technology. However, this fast expansion and use make likely their release into the environment with particular concerns for the aquatic ecosystems, which tend to be the ultimate sink for this type of contaminants. Considering the settling behaviour of particulates, benthic organisms are more likely to be exposed to these compounds. In this way, the present review aims to summarise the most recent data available from the literature on ENMs behaviour and fate in aquatic ecosystems, focusing on their ecotoxicological impacts towards marine and estuarine bivalves. The selection of ENMs presented here was based on the OECD's Working Party on Manufactured Nanomaterials (WPMN), which involves the safety testing and risk assessment of ENMs. Physical-chemical characteristics and properties, applications, environmental relevant concentrations and behaviour in aquatic environment, as well as their toxic impacts towards marine bivalves are discussed. Moreover, it is also identified the impacts derived from the simultaneous exposure of marine organisms to ENMs and climate changes as an ecologically relevant scenario.

The ecotoxicological effects of microplastics on aquatic food web, from primary producer to human: A review.

The prevalence of microplastics in global waters raises the concern about their potential effects on aquatic biota. In aquatic environment, microplastics are almost ubiquitously present in all compartments from surface water to benthic sediment, making them accessible to a wide range of aquatic biota occupying different habitats. Exposure to microplastics may induce detrimental implications to the health of aquatic organisms. This review describes the wide occurrence of microplastics ingestion by aquatic fauna and evaluates the ecotoxicological effects of microplastics as well as the associated chemicals on aquatic biota including phytoplankton and fauna from both freshwater and marine environments. Trophic transfer of microplastics and associated contaminants along the aquatic food chain and potential impacts on human health are also discussed. Finally, this review emphasizes the current knowledge gaps and gives recommendations for the future work.

Rice busk biochar treatment to cobalt-polluted fluvo-aquic soil: speciation and enzyme activities.

Rice busk biochar was mixed with cobalt (Co)-polluted soil to examine the efficacy of biochar for Co immobilization and detoxification in fluvo-aquic soil. The Co speciation (modified BCR sequential extraction), fluorescein diacetate (FDA) hydrolysis and soil enzyme activities were investigated. In soil, the Co ions (acid-soluble fraction) could be uptake by biochar due to the microporous structure on the surface, as well as the oxygen-containing functional groups and conjugated structure in the molecular structure. Therefore, when the biochar concentration was lower than the optimum concentration (~6 g·kg-1), there was transformation of Co from the acid-soluble fraction to the oxidizable fraction, resulting in lower environmental risk. However, if the biochar concentration continued increasing, the distribution coefficient of Co in the acid-soluble fraction increased (P < 0.05). The biochar could also reduce the toxicity of Co, resulting in the negative correlations between soil enzyme activities (FDA hydrolysis, urease and alkaline phosphatases) and Co in the acid-soluble fraction (r = -0.816, -0.928 and -0.908, respectively, P < 0.01). When the biochar concentration ranged from 5.83 to 6.76 g·kg-1, the efficacy for Co immobilization and detoxification reached the maxima. To conclude, in fluvo-aquic soil, rice busk biochar is an effective amendment for immobilizing Co ions and reducing the toxicity of Co. The biochar concentration in soil should range from 5.83 to 6.76 g·kg-1 to reach the optimum efficacy.

Active soil microbial composition and proliferation are directly affected by the presence of biocides from building materials.

Combinations of biocides are commonly added to building materials to prevent microbial growth and thereby cause degradation of the façades. These biocides reach the environment by leaching from façades posing an environmental risk. Although ecotoxicity to the aquatic habitat is well established, there is hardly any data on the ecotoxicological effects of biocides on the soil habitat. This study aimed to characterize the effect of the biocides terbutryn, isoproturon, octhilinone, and combinations thereof on the total and metabolically active soil microbial community composition and functions. Total soil microbial community was retrieved directly from the nucleic acid extracts, while the DNA of the active soil microbial community was separated after bromodeoxyuridine labeling. Bacterial 16S rRNA gene and fungal internal transcribed spacer region gene-based amplicon sequencing was carried out for both active and total, while gene copy numbers were quantified only for the total soil microbial community. Additionally, soil respiration and physico-chemical parameters were analyzed to investigate overall soil microbial activity. The bacterial and fungal gene copy numbers were significantly affected by single biocides and combined biocide soil treatment but not soil respiration and physico-chemical parameters. While the total soil microbiome experienced only minor effects from single and combined biocide treatment, the active soil microbiome was significantly impacted in its diversity, richness, composition, and functional patterns. The active bacterial richness was more sensitive than fungal richness. However, the adverse effects of the biocide combination treatments on soil bacterial richness were highly dependent on the identities of the biocide combination. Our results demonstrate that the presence of biocides frequently used in building materials affects the active soil microbiome. Thereby, the approach described herein can be used as an ecotoxicological measure for the effect on complex soil environments in future studies.

Mechanisms of harmful effects of Microcystis aeruginosa on a brackish water organism Moina mongolica based on physiological and transcriptomic responses.

To investigate the detrimental impacts of cyanobacterial bloom, specifically Microcystis aeruginosa, on brackish water ecosystems, the study used Moina mongolica, a cladoceran species, as the test organism. In a chronic toxicology experiment, the survival and reproductive rates of M. mongolica were assessed under M. aeruginosa stress. It was observed that the survival rate of M. mongolica fed with M. aeruginosa significantly decreased with time and their reproduction rate dropped to zero, while the control group remained maintained stable and normal reproduction. To further explore the underlying molecular mechanisms of the effects of M. aeruginosa on M. mongolica, we conducted a transcriptomic analysis on newly hatched M. mongolica cultured under different food conditions for 24 h. The results revealed significant expression differences in 572 genes, with 233 genes significantly up-regulated and 339 genes significantly down-regulated. Functional analysis of these differentially expressed genes identified six categories of physiological functional changes, including nutrition and metabolism, oxidative phosphorylation, neuroimmunology, cuticle and molting, reproduction, and programmed cell death. Based on these findings, we outlined the basic mechanisms of microcystin toxicity. The discovery provides critical insights into the mechanisms of Microcystis toxicity on organisms and explores the response mechanisms of cladocerans under the stress of Microcystis.

Unveiling the ecotoxicological impact of microplastics on organisms - the persistent organic pollutant (POP): A comprehensive review.

Microplastics have been ubiquitous in our environment for decades, and numerous studies have revealed their extensive dispersion, reaching far beyond the surface of the land, soil, aquatic ecosystems. They have infiltrated the food-chain, the food web, even the air we breathe, as well as the water we drink. Microplastics have been detected in the food we consume, acting as vectors for hazardous chemicals that adhere to their hydrophobic surfaces. This can result in the transfer of these chemicals to the aquatic life, posing a threat to their well-being. The release of microplastics into different environmental settings can give rise to various eco-toxicological implications. The substantial body of literature has led scientists to the consensus that microplastic pollution is a global problem with the potential to impact virtually any type of ecosystem. This paper aims to discuss crucial information regarding the occurrence, accumulation, and ecological effects of microplastics on organisms. It also highlights the new and emerging disease named "Plasticosis" that is directly linked to microplastics and its toxicological effects like permanent scarring and long-term inflammation in the digestive system of the seabirds. By comprehending the behaviour of these microplastic pollutants in diverse habitats and evaluating their ecological consequences, it becomes possible to facilitate a better understanding of this toxicological issue.

Cement pastes containing air entraining agent release the biocide octylisothiazolinone posing ecotoxicological effects.

We investigated whether cement pastes are a possible source of ecotoxicologically potent substances. For this purpose, leaching according to DIN EN 16637-2 was performed on portland cement pastes as well as blast furnace slag cement with and without an air entraining agent (AEA). The AEA, consisting of wood rosin and resin, contained the stabiliser drometrizole and the biocide octylisothizolinone (OIT), which was confirmed by our non-target screening (NTS). Our ecotoxicological studies (Daphnia magna, Aliivibrio fischeri and Desmodesmus subspicatus) of the pure cement eluates showed no effects at all. In these samples, it was possible to attribute up to 85 % of the dissolved organic carbon (DOC) to acetate, formate and diethylene glycol (DiEG). Eluates from cements with AEA contained up 70 µg/L octylisothizolinone (OIT), and no drometrizole was found. 90 % of the total OIT release happened within the first 6 h. It was possible to attribute the observed ecotoxicological effects mainly to the OIT concentrations. Additional leaching with elevated sulphate concentrations (800 mg/l) did not influence the release of DOC and OIT or increase the ecotoxicological effects. As a consequence, we advise curing the cement paste for 24 h prior to use, as this largely avoids the release of OIT and the observed ecotoxicological effects.

The Lethal and Sub-Lethal Effects of Fluorinated and Copper-Based Pesticides-A Review.

In recent decades, pollution levels have increased, mainly as a result of the intensive anthropogenic activities such industrial development, intensive agricultural practices, among others. The impact of metals and organic contaminants is, nowadays, a great concern to the scientific and political communities. Copper compounds are the main sold pesticides in Europe, as well as herbicides, including glyphosate. Diphenyl ethers are the second ones most sold. Glyphosate and copper compounds are intensively studied, but the opposite is seen in the case of diphenyl ethers, including fluorinated pesticides (e.g., oxyfluorfen). Some research has been performed to increase the knowledge about these contaminants, daily inputted on the aquatic systems and with dangerous effects at physical and biochemical levels on the organisms. A wide range of biomarkers (e.g., growth, survival, reproductive success, enzymatic activity, lipid metabolism) has been applied to determine the potential effects in many species. This review intends to: (a) perform a compilation of the knowledge in previous research about the action mode of organic (fluorinated-based herbicide) and inorganic (copper-based pesticides) contaminants; (b) carry out an information survey about the lethal and sub-lethal effects of the fluorinated-based pesticides, namely the oxyfluorfen and the copper-based pesticides, on aquatic species from different trophic levels, according to in vitro and in vivo studies; (c) understand the impact of oxyfluorfen and copper-based pesticides, considering their effects reported in in vitro studies and, simultaneously, the authorized concentrations by legal organizations and the effective concentrations of each pollutant found in the environment. The literature analyzed revealed noxious effects of Cu and oxyfluorfen to aquatic organisms, including freshwater and marine species, even when exposed to the reference as well as to environmental concentrations, thus highlighting the importance of more monitoring and ecotoxicological studies, to chemical pollutants and different species from different ecological niches, to sustain and improve the legislation.

Ecotoxicological effects of antibiotic adsorption behavior of microplastics and its management measures.

Microplastics adsorb heavy metals and organic pollutants to produce combined pollution. Recently, the adsorption behavior of antibiotics on microplastics has received increasing attention. Exploring the sorption behavior of pollutants on microplastics is an important reference in understanding their ecological and environmental risk studies. In this paper, by reviewing the academic literature in recent years, we clarified the current status of research on the adsorption behavior of antibiotics on microplastics, discussed its potential hazards to ecological environment and human health, and summarized the influence of factors on the adsorption mechanisms. The results show that the adsorption behavior of antibiotics on microplastics is controlled by the physical and chemical properties of antibiotics, microplastics, and water environment. Antibiotics are adsorbed on microplastics through physical and chemical interactions, which include hydrophobic interaction, partitioning, electrostatic interaction, and other non-covalent interactions. Intensity of adsorption between them is mainly determined by their physicochemical properties. The basic physicochemical properties of the aqueous environment (e.g., pH, salinity, ionic strength, soluble organic matter content, and temperature) will affect the physicochemical properties of microplastics and antibiotics (e.g., particle size, state of dispersibility, and morphology), leading to differences in the type and strength of their interactions. This paper work is expected to provide a meaningful perspective for better understanding the potential impacts of antibiotic adsorption behavior of microplastics on aquatic ecology and human health. In the meantime, some indications for future related research are provided.

Ecotoxicological and biochemical effects of a binary mixture of pesticides on the marine diatom Thalassiosira weissflogii in a scenario of global warming.

Under the current scenario of global warming, it is ecologically relevant to understand how increased temperature influences the combined toxicity of pesticides to aquatic species. Hence, this work aims to: a) determine the temperature effect (15 °C, 20 °C and 25 °C) on the toxicity of two pesticides (oxyfluorfen and Copper (Cu)), on the growth of Thalassiosira weissflogii; b) assess whether temperature affects the type of toxicity interaction between these chemicals; and c) assess the temperature effect on biochemical responses (fatty acids (FA) and sugar profiles) of the pesticides on T. weissflogii. Temperature increased the tolerance of the diatoms to the pesticides with EC50 values between 3.176 and 9.929 µg L-1 for oxyfluorfen and 42.50-230.75 µg L-1 for Cu, respectively, at 15 °C and 25 °C. The mixtures toxicity was better described by the IA model, but temperature altered the type of deviation from dose ratio (15 °C and 20 °C) to antagonism (25 °C). Temperature, as well as the pesticide concentrations, affected the FA and sugar profiles. Increased temperature increased saturated FA and decreased unsaturated FA; it also affected the sugar profiles with a pronounced minimum at 20 °C. Results highlight effects on the nutritional value of these diatoms, with potential repercussion on food webs.

Polycyclic aromatic hydrocarbon (PAH) leachates from post-consumption waterpipe tobacco waste (PWTW) into aquatic environment- a primary study.

Post-consumption waterpipe tobacco waste (PWTW) is an unrecognized type of hazardous waste that is produced and released in large quantities into the aquatic environment. It may contain high amounts of various pollutants including PAH, and to date, there has been no research on the potential for contamination by PAH from PWTW leaching into aquatic environments. In this study, the concentrations of PAH via PWTW of fruit-flavored and traditional tobacco leachate into three water types, including distilled water (DW), tap water (TW) and sea water (SW) at different contact times were evaluated. There were significantly higher concentration levels of Æ©PAH in waters with leachates from fruit-flavored PWTW than traditional tobacco (P-value<0.05). The concentration levels of Æ©PAH in DW, TW and SW at a total contact time of two months ranged from 0.13 to 3.51, 0.12 to 3.63 and 0.11-3.64 µg/L, respectively. Lower molecular weight PAH such as naphthalene (Naph), acenaphthylene (Acen) and fluorine (Flu) were detected in leachates immediately after a short contact time of 15 min. Higher molecular weight PAH including benzo [a]anthracene (BaA), benzo [b]fluoranthene (BbF), benzo [k]fluoranthene (BkF), chrysene (Chr), and benzo [a]pyrene (BaP) were detected after one month contact time, while indeno [1,2,3-cd] pyrene (Indp), benzo [ghi]perylene (BghiP) and dibenz [a,h]anthracene (DahA) were only observed at the contact time measurement of two months. By adding sodium azide as an antimicrobial agent and chemical preservative to SW samples, higher concentrations of PAH including IP, DahA and BghiP were observed. The concentration levels of PAH in water samples after two months contact time were higher than water quality standards provided by the World Health Organization (WHO) and other international organizations.

A multibiomarker approach to assess the ecotoxicological effects of diclofenac on Asian clam Corbicula fluminea (O. F. Müller, 1774).

Diclofenac (DCF), one of the most current and widely used nonsteroidal anti-inflammatory drugs (NSAIDs), has been frequently detected in aquatic environments worldwide. However, the ecotoxicological effects of DCF on freshwater invertebrates remain largely unknown. In the present study, Corbicula fluminea were exposed to environmentally relevant concentrations of DCF (0, 2, 20, and 200 µg/L) for 28 days, and the potential adverse effects of DCF on siphoning behavior, antioxidant responses, and apoptosis were investigated. Our results showed that the siphon efficiencies of clams were significantly suppressed under DCF stress. DCF exerted neurotoxicity via reducing the activity of acetylcholinesterase (AChE) in gills and digestive gland of C. fluminea. Exposure to DCF induced antioxidant stress and increased malondialdehyde (MDA) levels in both gills and digestive gland of C. fluminea. Transcriptional alterations of apoptosis-related genes indicated that DCF might induce apoptosis by triggering mitochondrial apoptotic pathway. These findings can improve our understanding of the ecological risk of DCF in freshwater ecosystems.

Comparison of the toxic effects of organic and inorganic arsenic in Caenorhabditis elegans using a multigenerational approach.

Although arsenic (As) is a persistent contaminant in the environment, few studies have assessed its effects over generations, as it requires an animal model with a short lifespan and rapid development, such as the nematode Caenorhabditis elegans. Furthermore, few studies have evaluated the effects of As metabolites such as dimethylarsinic acid (DMAV), and several authors have considered DMA as a moderately toxic intermediate of As, although recent studies have shown that this chemical form can be more toxic than inorganic arsenic (iAs) even at low concentrations. In the present study, we compared the toxic effects of arsenate (AsV) and DMAV in C. elegans over 5 subsequent generations. We evaluated biochemical parameters such as reactive oxygen species (ROS) concentration, the activity of antioxidant defense system (ADS) enzymes such as catalase (CAT) and glutathione-S-transferase (GST), and nonenzymatic components of ADS such as reduced glutathione (GSH) and protein-sulfhydryl groups (P-SH). Exposure to 50 µg L-1 of AsV led to an increase in ROS generation and GSH levels together with a decrease in GST activity, while exposure to DMAV led to an increase in ROS levels, with an increase in lipid peroxidation, CAT activity, and a decrease in GSH levels. In addition, both treatments reduced animal growth from the third generation onward and caused disturbances in their reproduction throughout all 5 generations. This study shows that the accumulated effects of DMA need to be considered; it highlights the importance of this type of multigenerational approach for evaluating the effects of organic contaminants considered low or nontoxic.

Ecotoxicological effects and bioaccumulation in Eichhornia crassipes induced by long-term exposure to triclosan.

In this study, the ecotoxicological effects and bioaccumulation of triclosan (TCS) in Eichhornia crassipes (E. crassipes) were investigated with 28 d exposure experiments. The results showed that chlorophyll content was increased after 7 d exposure to 0.05-0.1 mg L-1 TCS, while it was inhibited significantly by 0.5 mg L-1 TCS after 21 d exposure. The concentrations of soluble protein in the leaves increased during the initial stage (7 d and 14 d), whereas they decreased during 21 d and 28 d. The concentrations of soluble protein in the roots gradually reduced during the exposure time. The antioxidant enzyme activities in roots decreased continually with the exposure time. However, the antioxidant enzyme (SOD and CAT) activities in leaves decreased after exposure longer than 14 d. Moreover, differentially expressed genes (DEGs) were observed in the root of E. crassipes after a 28 d exposure to 0.5 mg L-1 TCS, with 11023 DEGs down-regulated and 3947 DEGs up-regulated. 5 SOD down-regulated genes and 3 CAT down-regulated genes were identified from transport and catabolism in cellular processes. After 28 d exposure, the TCS content in roots and leaves stressed by 0.5 mg L-1 TCS were up to 13.04 µg g-1 and 1.97 µg g-1, respectively. SOD in leaves was negatively correlated with TCS content in leaves, CAT in roots was negatively correlated with TCS content in roots. These results provide experimental data to assess the ecological risk of TCS with long exposure in aquatic systems.

Fluoroquinolone antibiotics: Occurrence, mode of action, resistance, environmental detection, and remediation - A comprehensive review.

Antibiotics play an essential role in the medical healthcare world, but their widespread usage and high prevalence have posed negative environmental consequences. During the past few decades, various antibiotic drugs have been detected in aquatic and terrestrial ecosystems. Among them, the Fluoroquinolones (FQ) group is ubiquitous in the environment and has emerged as a major environmental pollutant. FQs are very significant, broad-spectrum antibiotics used in treating various pathogenic diseases of humans and animals. The most known and used FQs are ciprofloxacin, norfloxacin, ofloxacin, levofloxacin, enrofloxacin, danofloxacin, and moxifloxacin. After human and animal administration, about 70% of these drugs are excreted out in unaltered form into the environment. Besides, wastewater discharge from pharmaceutical industries, hospitals, and agriculture runoff is the major contributor to the accumulation of FQs into the ecosystem. Their long-term presence in the environment creates selection pressure on microorganisms and contributes to the emergence of multi-drug-resistant bacteria. In addition to the resistance, these antibiotics also impose ecotoxicological effects on various animals and plant species. The presence of the fluorine atom in Fluoroquinolones makes them highly electronegative, strong, recalcitrant, and less compatible with microbial degradation. Many biological and chemical processes have been invented and successfully implemented during the past few decades for the elimination of these pollutants from the environment. This review provides a detailed overview of the classification, occurrence, distribution, and ecotoxicological effects of Fluoroquinolones. Their modes of action, resistance mechanism, detection and analysis methods, and remediation strategies have also been discussed in detail.

Response of submerged macrophytes and leaf biofilms to different concentrations of oxytetracycline and sulfadiazine.

Oxytetracycline and sulfadiazine were widely used and they entered the environment through various channels such as domestic sewage, medical wastewater and agricultural wastewater, causing significant ecological risk. To determine the effects of different antibiotic concentrations on submerged macrophytes, Vallisneria natans was exposed to solutions containing different concentrations of oxytetracycline and sulfadiazine (0.1 mg/L、1 mg/L、10 mg/L、50 mg/L). After 20-days exposure, we found that 10 mg/L groups had a significant effect on Vallisneria natans. Under high antibiotic concentrations, the growth of Vallisneria natans was inhibited, chloroplasts were deformed, the chlorophyll content was reduced, and antioxidant enzyme activities, such as superoxide dismutase and glutathione, were increased. There was no significant difference between the control group and groups with low antibiotic concentrations (≤1 mg/L). The N-acyl-l-homoserine lactone concentration tended to increase with increasing antibiotic concentrations. The presence of antibiotics also affected the microbial community structure of biofilms on the submerged macrophytes. For example, the higher the concentration of antibiotics, the higher the proportion of Proteobacteria. These results suggest that high concentrations of oxytetracycline and sulfadiazine can disrupt homeostasis, induce effective Vallisneria natans defense mechanisms and alter biofilms in aquatic ecosystems.