Anthropogenic pollution of aquatic ecosystems: Emerging problems with global implications

Ecotoxicological impact of the fungicide tebuconazole on fish: a historical review, global trends and challenges

Tebuconazole (TBZ) is a triazole fungicide broadly used to control fungal diseases in agricultural crops, fruit-bearing plants and forestry plantations. However, its increasing use and release into aquatic environments has raised concerns about its hazardous effects on the health of fish. Thus, the aim of the present study was to review the scientific literature on the ecotoxicological effects of TBZ and TBZ-based commercial formulations on fish. Historical review data (publication year and geographical distribution), TBZ type, experimental design, fish species, habitat, life stage, tissue/organ, lethal concentration (LC50), concentration and exposure time, biomarkers and effects were compiled and critically analyzed. Studies were mainly conducted with freshwater species at adult and larval stages, whereas no data were find for marine fish species. Zebrafish, (Danio rerio) was the most assessed species. Both TBZ and TBZ-based commercial formulations induced oxidative stress, endocrine disruption, neurotoxicity, genotoxicity, histopathologies, behavior impairments and mortality on fish. TBZ can induce synergistic and antagonistic effects on fish when it is combined to other pesticides. Overall, the current study has shown the potential hazardous effects of TBZ and TBZ-based commercial formulations on the health of fish.

Associations between metals and metalloids, oxidative stress and genotoxicity in Nurse sharks Ginglymostoma cirratum from the Brazilian Amazon Coast

Elasmobranch populations have significantly declined in recent decades due to anthropogenic activities, with chemical contamination comprising one of the main threats to this group. Although some biochemical biomarkers have been utilized to assess elasmobranch health, especially concerning metal and metalloid contamination, associations with genotoxic biomarkers are still scarce and non-existent for Brazilian Amazon coast sharks. Herein, metals, metalloids, reduced glutathione (GSH), glutathione S-transferase (GST), metallothionein (MT), and nuclear anomalies (micronucleus, nuclear buds, and bilobed cells) were determined in gills, liver, and muscle tissues of Nurse sharks (Ginglymostoma cirratum) from the São Marcos Estuarine Complex, Maranhão, Brazil. Females exhibited significantly higher As concentrations in muscle (23.14 ± 13.98 μg g-1) and gills (4.53 ± 2.10 μg g-1) compared to males (3.98 ± 2.61 μg g-1 and 1.51 ± 0.41 μg g-1, respectively) (p < 0.05). Males showed higher Se concentrations in muscle (0.52 ± 0.02 μg g-1) compared to females (0.32 ± 0.09 μg g-1) (p < 0.05), while Rb levels were higher in male liver (0.28 ± 0.05 μg g-1) than in females (0.18 ± 0.04 μg g-1) (p = 0.001). No significant differences were observed for Hg, Ti or rare earth elements (Ce and La) between sexes (p > 0.05). Higher GSH concentrations and GST activities were noted in gills and liver, while MT concentrations were higher in muscle. Low genotoxic damage frequency was observed, likely due to the species' sedentary lifestyle and efficient DNA repair system. Moderate to strong correlations between metals/metalloids and biochemical/genotoxic responses were detected, particularly in females, highlighting the protective role of GST against DNA damage. Protective effects of Se against Hg were observed in the liver. Metal concentrations did not exceed regulatory limits, although bioaccumulation patterns and physiological responses suggest that Nurse sharks are exposed to environmental contamination, with As and Se accumulation.

Persistent elevated levels of dissolved lead in the Indian Ocean post-leaded gasoline ban: The impact of anthropogenic activities, sediment desorption, and dust storms

This study examines the distribution of dissolved lead (dPb) in the Indian Ocean, based on seawater samples collected during winter monsoon GI10 (2020) and spring inter-monsoon GI09 (2021) cruises. A total of 510 samples were analyzed for dPb concentrations using HR-ICP-MS coupled with seaFAST system. The study emphasizes the spatial distribution of dPb in the Indian Ocean, identifying major sources and key influencing factors. Concentrations of dPb in the mixed layer ranged from 23 to 114 pM, with elevated values in the northern Indian Ocean. A pronounced latitudinal gradient was observed as the dPb concentration decreased from north to south. The atmospheric lead fluxes range from 35-1439 Mmol y-1 in the Arabian Sea and 22-281 Mmol y-1 in the Bay of Bengal, while lead contributions from continental shelf sediments vary between 1.8-2 Mmol y-1 and 5.9-10.7 Mmol y-1, respectively. Atmospheric deposition is the dominant source of dPb in both basins. However, the substantially higher Pb contribution from continental shelf sediments in the Bay of Bengal highlights the impact of enhanced sediment loading, primarily driven by the Ganga-Brahmaputra River system. Among the Asian countries, China and India have exhibited a substantial rise in lead emissions by coal combustion, with an increase of approximately 4.3 to 4.8 times over a last 33-year period, amounting to 12.5×103 and 82.8×103 tons y-1 for India and China respectively in 2023, highlighting their rapid industrialization and heavy reliance on coal. Apart from coal combustion, climatic events such as the Indian Ocean Dipole (IOD), which controls dry/wet conditions, dust storms, and bushfires, play a substantial role in the addition of dPb over the southern Indian Ocean.

Non-synergistic effects of microplastics and submerged macrophytes on sediment microorganisms involved in carbon and nitrogen cycling

Submerged macrophyte communities play a crucial role in regulating sediment carbon and nitrogen cycling in lake ecosystems. However, their interactions with emerging pollutants such as polystyrene microplastics (PS-MPs) remain poorly understood. In this study, we employed metagenomic analysis to examine the combined effects of submerged macrophyte communities and PS-MPs on sediment microbial communities, focusing on microbial populations, functional genes, and metabolic pathways involved in carbon and nitrogen cycling. Our results revealed a non-synergistic interaction between macrophyte communities and PS-MPs in shaping sediment biogeochemical processes. While increasing PS-MPs concentrations (from 0.5 to 2.5 % w/w) significantly enhanced microbial diversity (species richness increased from 533 to 1301), the presence of macrophytes moderated this response. Notably, we observed differential selective pressures on functional genes involved in key carbon and nitrogen cycling steps, particularly amoAB and amoC, nirS, and nirK, indicating distinct shifts in microbial functional groups. Furthermore, we identified complex substrate-pathway interactions: nitrate and ammonium differentially influenced fermentation and methanogenesis, while inorganic carbon positively regulated nitrate dissimilatory reduction. These findings provide novel insights into the regulatory mechanisms of submerged macrophytes in sediment biogeochemical cycling under microplastic stress, highlighting their potential role in maintaining ecosystem functions in contaminated aquatic environments.

Eutrophication mitigates Cu-induced inhibition on growth and photosynthetic performance in the marine diatom Thalassiosira weissflogii

Eutrophication and metal pollution threaten coastal ecosystems, yet interactions between these stressors are insufficiently explored. This study investigated how nitrogen (N) and copper (Cu) levels impact the physiology of the marine diatom Thalassiosira weissflogii. Results indicate that high nitrogen (HN) conditions significantly alleviate copper's inhibitory effects on chlorophyll a (Chl a) synthesis, growth rate (μ), and photosynthetic performance. Under low nitrogen (LN) conditions, high Cu exposure reduced Chl a content and growth rates by up to 72 % and 55 %, respectively, while reductions under HN were less severe (56 % for Chl a, 20 % for growth). Higher relative electron transport rate (rETR) and gross oxygen release by PS II (GO) under HN across Cu concentrations suggest that N enrichment buffers the toxicity of Cu on this diatom by potentially enhancing PSII activity. These findings underscore the role of nutrient-metal interactions in ecosystem management, highlighting how eutrophication may mitigate heavy metal stress in coastal waters.

Combined effects of polyamide microplastics and the pathogenic bacterium Vibrio parahaemolyticus on the immune parameters of Mytilus coruscus

The thick-shelled mussel, Mytilus coruscus, plays a vital role in marine ecosystems but is vulnerable to pollutants. Polyamide microplastics (PA-MPs), such as nylon, can adsorb harmful bacteria like Vibrio parahaemolyticus, posing threats to bivalves and economic risks to aquaculture. In this study, M. coruscus was exposed to four treatments over 14 days: (1) control, (2) PA microplastics (50 particles/L), (3) V. parahaemolyticus (1011 CFU/L), and (4) combined PA and V. parahaemolyticus. Evaluations included gill tissue pathology, bacterial loads in mussel tissues, and antioxidant and immune enzyme activities in hemolymph. Results showed that co-exposure to PA microplastics and V. parahaemolyticus led to gill tissue damage, such as decreased gill epithelial thickness and hemocytic infiltration. In addition, mussels exhibited elevated oxidative stress in the hemolymph, as indicated by increased levels of hydrogen peroxide (H₂O₂), superoxide anion (O₂·-), and malondialdehyde (MDA). Concurrently, immunological activity was suppressed, as evidenced by reduced activities of alkaline phosphatase (AKP), acid phosphatase (ACP), and lysozyme (LZM). Notably, PA microplastics appeared to facilitate the clearance of V. parahaemolyticus by the mussels. These findings contribute to sustainable aquaculture and shellfish safety strategies.

Vegetation morphology and phytobiology intervene in heavy metal contamination of surface sediments in Yangtze River Estuary

Accumulation of heavy metals in estuaries can represent potential risks to the aquatic environment and public health. Estuarine coastal vegetation's physical form and biological function have important effects on dynamic processes and migration of pollutants in estuaries. Field observations were conducted at sites SJG and LHK in the Yangtze River Estuary (YRE) from September 2021 to February 2022 and September 2022 to December 2022. Site LHK (Liuhekou) represents a typical natural environment, whereas Site SJG (Sanjiagang) is more significantly influenced by anthropogenic activities. At both sites, samples of unvegetated sediments, vegetated sediment, and vegetation were collected and analyzed for six heavy metals (As, Cd, Cr, Pb, Cu, Zn). The sequence of heavy metal concentrations in both sediments and vegetation was as follows: Zn > Cr > As > Pb > Cu > Cd. The results of the contamination assessment indicated that the risk of heavy metal contamination was higher at SJG than at LHK. Cr, As, and Cd were identified as pollutants, with Cd posing the main potential ecological risk. Correlation and principal component analyses indicated that anthropogenic emissions and atmospheric deposition were the main sources of heavy metal contamination, with vegetation exhibiting elemental variability in heavy metal interception. Phytobiological analyses of the pollutant elements Cr, As, and Cd indicated that phytobiology's attenuation of sediment heavy metal contamination was significant based on metabolic processes. However, the hyper-enrichment of Cd was independent of metabolism, with its concentration stabilizing around biotoxic levels. The results in this paper promote a deeper understanding of heavy metal mitigation under the biological effectiveness of vegetation in coastal areas of the Yangtze River Estuary. The proposed analytical method provides ideas for the study of contaminant partitioning under the influence of vegetation in estuaries and coastal water environments.

The impact of salinity on heavy metal accumulation in seaweed

Aquatic heavy metal pollution, driven by industrialization and climate change, threatens marine ecosystems through bioaccumulation. Climate-induced salinity fluctuations influence metal speciation and bioavailability in coastal environments. Seaweeds, crucial for nutrient cycling and economic use, exhibit species-specific metal uptake under varying salinity conditions. This study employs bibliometric analysis to examine research trends from 1995 to 2024 on the impact of salinity on metal accumulation in seaweeds. A search conducted on 8 October 2024 resulted in 242 articles, which were then filtered to 28 relevant studies for analysis. Using the Web of Science Core Collection, these articles were analyzed with VOSviewer and Bibliometrix to identify key contributors, collaborations, and research themes. Results reveal a growing academic interest since 2006, with increasing citation counts reflecting global concern over salinity and heavy metal pollution. Significant contributions from Brazil and Portugal, alongside strong European collaborations, highlight regional strengths. Five key themes emerge, encompassing seaweed physiology, biomonitoring, and phytoremediation. Findings indicate that salinity fluctuations significantly affect metal bioavailability and uptake in seaweeds, influenced by species-specific factors, temperature, and pH. This study highlights the need for targeted, site-specific research on diverse seaweed species to effectively manage heavy metal pollution in coastal ecosystems, particularly in light of climate change and industrial activities. Additionally, the research emphasizes the potential of seaweeds as bioindicators and bioremediators in environmental monitoring and pollution management.

Accessible water quality monitoring through hybrid human-machine colorimetric methods

Effective water quality monitoring is important for environmental protection and public health, yet conventional field and laboratory methods each present significant limitations. Field tools such as colorimetric test strips offer affordability and accessibility but are prone to subjective interpretation and environmental variability. In contrast, laboratory-based techniques provide high precision but are costly, resource-intensive, and less feasible in decentralized contexts. This study presents a hybrid human-machine methodology that improves the accuracy and reproducibility of colorimetric test strip analysis while maintaining field-level accessibility. A total of 34 water samples collected along a 7-km stretch of Seunggi Stream in Incheon, South Korea, were analyzed using a web-based platform that extracts RGB values from images of test strips and reference charts. To translate color into concentration, the system calculates Euclidean distances between test strip colors and known reference values, then applies inverse distance weighting (IDW) to interpolate continuous estimates from the closest matches. This approach overcomes the limitations of discrete reference charts, enabling more precise and reproducible readings without the need for complex machine learning models. Validation against standard laboratory methods revealed strong correlations (r > 0.85 for pH, lead, and total hardness), supporting the reliability of the approach. Spatial trends in pollutants were successfully mapped, demonstrating the method's utility for environmental monitoring. This cost-effective, scalable solution bridges the gap between subjective field testing and laboratory precision, offering a practical tool for resource-limited settings, citizen science, and preliminary assessments. Future research will refine analyte-specific accuracy and expand applicability to more diverse conditions.

Autonomous wave gliders as a tool to characterize delphinid habitats along the Florida Atlantic coast

As climate change and anthropogenic activities continue to impact cetacean species, it becomes increasingly urgent to efficiently monitor cetacean populations. Continuing technological advances enable innovative research methodologies which broaden monitoring approaches. In our study, we utilized an autonomous wave glider equipped with acoustic and environmental sensors to assess delphinid species presence on the east Florida shelf and compared this approach with traditional marine mammal monitoring methods. Acoustic recordings were analyzed to detect delphinid presence along the glider track in conjunction with subsurface environmental variables such as temperature, salinity, current velocity, and chlorophyll-a concentration. Additionally, occurrences of soniferous fish and anthropogenic noise were also documented. These in-situ variables were incorporated into generalized additive models (GAMs) to identify predictors of delphinid presence. The top-performing GAM found that location, sound pressure level (SPL), temperature, and chlorophyll-a concentration explained 50.8% of the deviance in the dataset. The use of satellite environmental variables with the absence of acoustic variables found that location, derived current speed and heading, and chlorophyll-a explained 44.8% of deviance in the dataset. Our research reveals the explanatory power of acoustic variables, measurable with autonomous platforms such as wave gliders, in delphinid presence drivers and habitat characterization.

Cadmium Contaminants in Pollen and Nectar Are Variably Linked to the Growth and Foraging Behaviors of Honey Bees

Cadmium (Cd) is a heavy metal present in pollen and nectar that affects pollinator attributes. Honey bees possess the ability to eliminate Cd from honey. Consequently, the concentration of Cd in pollen, rather than nectar, is the critical factor influencing the growth and foraging behavior of honey bees. However, there is a dearth of studies regarding the specific association by which the impact on bee growth and foraging behavior fluctuates in relation to the Cd dosage of pollen or nectar. We hypothesized that at low exposure levels, the amount of Cd in pollen would affect honey bee growth, and the amount of nectar influences honey bee foraging behavior. At high exposure levels, the amount of Cd in pollen and nectar would affect both honey bee growth and foraging behavior. A field experiment was performed in Sichuan (the average background value of Cd in soil is 5.6 times higher than other regions in China) to examine the impact of different soil Cd concentrations (low: 0.60 ± 0.05 mg·kg-1 (average ± SD); middle: 1.32 ± 0.08 mg·kg-1; high: 1.76 ± 0.10 mg·kg-1) on the Cd levels in plant organs (Brassica campestris), alongside the body mass and visitation rates of honey bees (Apis mellifera). Our results indicated in honey bees in the habitats with low concentrations of soil Cd that the Cd content in pollen was inversely correlated with the body mass of larvae, pupae, and worker bees. The quantity of nectar governed the foraging activity of honey bees in the habitats with low levels of soil Cd. At middle to high exposure levels, Cd concentrations in pollen and honey exerted a negative influence on honey bee development and foraging behavior. These findings offer novel insights into the impact of Cd on pollinator attributes, and the global decline of pollinators.

Effects of pyrimidine on cellular and neuronal arrangement, oxidative stress and energy content in the brain of the freshwater catfish, Heteropneustes fossilis

Fish are facing compromised health with mass mortality due to the decreased water quality of aquatic bodies. The brain, a complex body organ that controls whole body physiology, is influenced first by any kind of water fluctuations, and by keeping it relaxed and nourished, fish health can be improved. Among freshwater fish, catfish Heteropneustes fossilis has importance not only as a rich nutrient source but also due to medicinal significance. This study evaluated the impact of pyrimidine, a well-known organic compound with several therapeutic properties, on the cerebral health of the freshwater catfish H. fossilis as a bioremediation of aquatic environmental threats. In experiments, to get an effective concentration of pyrimidine, fish were incubated with different doses of pyrimidine (10 fg/mL-1 mg/mL) for 24 h, and brain histotexture and fish survival were recorded. As per the results of the previous experiment, an effective concentration of pyrimidine (10 pg/mL) was given for different durations (1-, 5- and 21-day incubation with pyrimidine and recovery; after 21-day treatment in only water for 7 days) along with the control group. Results exhibited that the level of cerebral antioxidant enzymes (catalase, superoxide dismutase, peroxidase) and lipid peroxidation were significantly lower, and macromolecules (carbohydrate, protein and lipid) were increased in pyrimidine-treated fish with duration of pyrimidine treatment as compared to the control group. Histo-neurological analysis of the brain with haematoxylin-eosin and cresyl violet revealed that an effective, nonlethal concentration of pyrimidine supported overall neuronal health without any histopathological changes. However, in the recovery experimental group, results showed reverting of pyrimidine induced positive changes in antioxidative enzyme and energy biomolecule levels, supporting the non-bio-accumulative nature of pyrimidine. However, microphotographs revealed that the neuronal quantity (cresyl violet) and cellular histotexture (haematoxylin-eosin) improvement due to pyrimidine were sustained in the recovery group. The results of this study suggested that effective concentration of pyrimidine improved the brain health of H. fossilis in a duration-dependent manner compared to control fish due to increased metabolism by upregulating energy macromolecule and cellular-neuronal texture along with downregulation of antioxidative stress.

Evaluation of heavy metal pollution and ecological risk of surface sediments in a tropical mountainous River-Estuary-Shelf Continuum system: A case study of the Selangor River, Malaysia

As human activities continue to increase, the global production of pollutants has increased significantly, with the majority of pollutants being transported to the ocean via rivers, resulting in intensified pollution in estuaries and coastal areas. To maintain a healthy marine ecological environment, it is necessary to consider rivers, estuaries, and coastal seas as integrated systems and implement pollution management based on the concept of land-ocean integration. In this study, heavy metal elements in the surface sediments of Selangor River-Estuary-Coastal Shelf Continuum were collected and analysed to assess their pollution levels and potential ecological risks. The results show that the heavy metal content is high in the downstream and estuarine regions, with a general decreasing trend observed from nearshore to offshore in the coastal shelf area. The heavy metal pollution assessment indicates that the surface sediments of the Selangor River-Estuary-Coastal Shelf continuum were contaminated, with the most severe pollution occurring downstream and within the estuary. The pollution levels gradually decrease after exiting the estuary. The ecological risk associated with heavy metal pollution in rivers, estuaries, and southeastern coastal areas was classified as moderate to serious, whereas other areas exhibited only slight ecological risks. Specifically, As causes serious pollution in the river and estuary, with moderate-to-serious pollution in the coastal shelf area and moderate-to-serious ecological risks, mainly originating from mining within the river basin. Pb causes moderate pollution in the river, estuary, and coastal areas, with slight ecological risks due to mining within the river basin and inputs from nearby rivers, ports, and industrial activities. Other heavy metals cause minor pollution and pose minimal ecological risks.

The feeding mode effect: influence on particle ingestion by four invertebrates from Sub-Antarctic and Antarctic waters

Microplastic (MP) pollution is a significant threat to marine environments not only due to its widespread presence but also because of the alarming emergence of ingestion records among benthic organisms. In this study, MP prevalence was assessed in the stomach of the crustaceans Lithodes santolla and Grimothea gregaria and the gastropods Nacella deaurata and N. concinna. Particles were analyzed with Fourier-transform infrared (FTIR) spectroscopy. Overall, the analysis revealed that the particles were mainly microfibers composed of cellulose/rayon (60%), followed by MPs (30%), and undetermined not registered in the library (10%). Higher prevalence was found in marine benthic grazers compared to scavengers, with the latter showing low particle prevalence in their stomach contents. Grazers presented a significantly higher abundance per individual but a lower size of ingested particles compared to scavengers. When grouped by trophic levels, tertiary consumers presented significantly lower abundances per individual but larger sizes of the ingested particles. Pearson's correlations showed no significant associations between particle abundance/size and species body size. The results of this study may suggest that continued MP pollution in marine environments and the associated accidental ingestion by marine organisms will alter the energy flow and organic matter availability in benthic food webs, with species that perform certain functional traits more susceptible to being affected.

Seasonal changes in bay water column properties and their influence on the distribution of dissolved and particulate substances along the south coast of Curaçao (Caribbean Sea)

As endpoints of watersheds, bays concentrate erosion- and human-derived substances such as dissolved inorganic nutrients and pollutants. We investigated the water movement and biogeochemistry of two bays in Curaçao: Piscadera Bay and Spaanse Water, during the dry (May 2022 and 2023) and wet seasons (November 2021 and 2023). Bay-ocean exchange was limited during the dry season, enhancing nutrient concentrations in the bays. The wet season showed increased mixing between bay and offshore water. Extreme rainfall from the 2023 El Niño event led to heavy runoff and wastewater influx, particularly in Piscadera Bay, where enriched δ15N and total xenobiotic concentrations were over 1.5 times higher than in the dry season. Elevated δ15N and δ13C values reflected greater terrestrial influence in Piscadera Bay. These findings show how extreme weather, likely under future climate scenarios, can enhance nutrient and pollutant export from bays to reefs.

The first eco-assessment of phytoplankton assemblages associated with environmental conditions of different lakes in the Western Black Sea basin of Türkiye

Lakes play a vital role in supporting biodiversity, providing water resources, regulating climate, cycling nutrients, and offering recreational opportunities. Despite their importance for environmental health and human well-being, lakes face significant pressures in the Anthropocene era. The present work seeks to assess the species-environment interactions and the ecological status of six lakes in the Western Black Sea basin of Türkiye utilizing phytoplankton metrics during wet and dry periods. Canonical correspondence analysis revealed a significant correlation equal to 98.5% between phytoplankton species and environmental stressors during two hydrological periods. Electrical conductivity (EC), pH, total organic carbon (TOC), and temperature were the most influential environmental factors affecting phytoplankton distribution in lakes (p = 0.002). Lake Sarıkum, a brackish habitat, was under high EC and pH pressure and is characterized by pollution-tolerant species. Lake Yeniçağa associated with TOC is characterized by some species, such as Anabaenopsis milleri, Chroococcus turgidus, Pseudoschroederia robusta, Aphanocapsa sp., Merismopedia glauca, Micractinium quadrisetum, and Microcystis aeruginosa. Lake Abant is located on the opposite side of EC, TOC, and temperature, which was associated with some species such as Cymbella affinis, Achnanthidium minutissimum, Encyonema minutum, E. silesiacum, and Dinobryon divergens. Results of the phyto-assessment displayed that the ecological status (ES) of the sampling stations during the rainy and dry periods varied from bad to high. The modified phytoplankton trophic index (MPTI) exhibited that a moderate ES was found in Lakes Sarıkum and Yeniçağa, while others had a good ES. The present study confirmed that phytoplankton communities are strongly linked to the ecological status of lakes in the Western Black Sea basin, which could be assessed using the MPTI.

The diving beetle, Cybister lateralimarginalis (De Geer, 1774), as a bioindicator for subcellular changes affected by heavy metal(loid) pollution in freshwater ecosystems

The present study assessed Cybister lateralimarginalis as a model species for ecotoxicological studies of metal(loid) bioaccumulation in freshwater ecosystems, by optimising protocols and analysing biomarker activities and metal(loid) concentrations from different sites and investigating their association. To accomplish this, levels of arsenic (As), selenium (Se), cadmium (Cd), mercury (Hg), and lead (Pb) were analysed, as well as a set of biomarkers were evaluated, esterase activity and oxidative stress biomarkers: fluorescence- and glutathione-based. C. lateralimarginalis were sampled in the spring/summer of 2023 along the Sava, Drava and Danube floodplains in Croatia. C. lateralimarginalis samples from Sava floodplain (Mužilovčica) showed altered carboxylesterase (CES) activity, lower glutathione (GSH) levels, and elevated Hg and As concentrations. The Weighted Pollution Index (WPI) indicated moderate pollution at the Sava floodplain, possibly due to agricultural or petrochemical impacts. At the Drava floodplain (Podravlje), higher glutathione S-transferase (GST) activity and elevated Cd, Hg, and As concentrations were observed, likely from soil accumulation, while Stara Drava beetles had lower GSH levels, suggesting agricultural impacts. Despite this, the Drava floodplain showed the lowest WPI. Higher GST activity was noted at the Danube floodplain (Kopački rit and Topoljski Dunavac), with reactive oxygen species (ROS) concentrations (Kopački rit and Podunavlje) possibly reflecting agricultural practices or illegal hunting. The present research successfully applied C. lateralimarginalis as a bioindicator species for assessing metal(loid)s in different environments, highlighting its reliability as an abundant apex predator, emphasizing the significance of integrating biomarker response evaluation into pollutant monitoring for efficient environmental risk assessment in freshwater ecosystems.

Diving into freshwater microbial metabolites: Pioneering research and future prospects

In practically every facet of life, especially nutrition, agriculture, and healthcare, microorganisms offer a prospective origin for abundant natural substances and products. Among these microorganisms, bacteria also possess the capability to rapidly acclimate to diverse environments, utilize varied resources, and effectively respond to environmental fluctuations, including those influenced by human activities like pollution and climate change. The ever-changing environment of freshwater bodies influences bacterial communities, offering opportunities for improving health and environmental conservation that remain unexplored. Herein, the study discusses the bacterial taxa along with specialised metabolites with antioxidant, antibacterial, and anticancer activity that have been identified from freshwater environments, thus achieving Sustainable Development Goals addressing health and wellbeing (SDG-3), economic growth (SDG-8) along with industrial development (SDG-9). The present review is intended as a compendium for research teams working in the fields of medicinal chemistry, organic chemistry, clinical research, and natural product chemistry.

The first Dugesia species (Platyhelminthes, Tricladida, Dugesiidae) documented for Saudi Arabia: an integrative description

Exploration of various freshwater bodies in the Kingdom of Saudi Arabia led to the discovery of a new species of Dugesia, thus representing the first documented record of freshwater planarians in this country and the second fully documented record of a naturally sexual population of a Dugesia species in the Arabian Peninsula. Based on morphological, karyological, anatomical, and molecular data, this Dugesia population from Saudi Arabia is here identified as representing a distinct, new species, Dugesia bursagrossa Harrath & Sluys, sp. nov. The species is characterized by the following anatomical features: dorsal testes; highly glandular, barrel-shaped penis papilla; vasa deferentia opening separately into the antero-dorsal portion of a small intrabulbar seminal vesicle; ejaculatory duct opening subterminally through the ventral side of the penis papilla; muscular penis bulb composed of intermingled longitudinal and circular muscles; two ovaries positioned ventrally at approximately one-third of the distance between the brain and the root of the pharynx; oviducts opening separately and at different levels into the vaginal portion of the bursal canal; very large copulatory bursa, occupying almost the entire ample space between the posterior wall of the pharyngeal pocket and the penis bulb; bursal canal lined with a nucleated epithelium and covered by subepithelial layers of longitudinal muscles, followed by layers of circular muscles. The karyotype of the new species exhibits mixoploidy, with diploid complements of 2n = 18 and triploid complements of 3n = 27 + 1B chromosomes, with all chromosomes being metacentric. Phylogenetic analysis based on the COI sequence indicates that D. bursagrossa is distinct from closely related species within the same clade, with strong support from the anatomical and karyological data.

Spatio-temporal pollution assessment of Kulfo River using CCME-WQI and pollution tolerance index by benthic macroinvertebrates, Arba Minch, Ethiopia

In developing nations, the biggest threat to public health is the quality of the water. The Kulfo River provides the majority demand of the domestic water and irrigation along its course; however, it is observed that wastes from anthropogenic and natural activities enter the river. Therefore, this study aimed to examine the pollution status by integrating conventional methods with benthic macroinvertebrates. One hundred twenty samples were collected for 15 water quality parameters from five sampling sites during dry and rainy events. The mean concentration of DO, TSS, BOD5, COD, ortho-phosphate, and turbidity did not meet the standard limits in five sampling sites during the rainy season. Benthic macroinvertebrates were collected from the left, middle, and right sides of the river for each sampling site and examined using the Benthos Biomonitoring Protocol Network Manual. CCME index and PTI index of benthic macroinvertebrates were used to examine the pollution status of the river. According to CCME index result, S2 (39.79), S3 (38.90), and S4 (37.71) are classified under poor pollution status during the rainy season and S1 (92.13) and S5 (95.70) are categorized as good and excellent pollution status in the dry season, respectively. On the contrary, based on the PTI index result, S2 (7.0), S3 (9.0), S4 (9.0), and S5 (9.0) are classified under poor pollution status during the rainy season, whereas S2 (14.0), S3 (10.0), and S4 (15.0) are categorized under fair, and sampling sites S1 (21.0) and S5 (20.0) have good pollution status in the dry season. Based on study findings, the Kulfo River is contaminated by pollutant intrusion, resulting in a decrease in its quality. Therefore, management of solid, liquid, runoff, and domestic activities is critical in upstream tributaries and Arba Minch town to prevent river water quality deterioration.

Analysis of Pollutant Accumulation in the Invasive Bivalve Perna viridis: Current Status in the Colombian Caribbean 2020-2023

The Colombian Caribbean faces environmental challenges due to urbanization, industrialization, and maritime activities, which introduce pollutants such as heavy metals, hydrocarbons, and microplastics into aquatic ecosystems. Perna viridis (Asian green mussel), an invasive species that has been established in Cartagena Bay since 2009, exhibits potential bioaccumulation capacity, making it a promising biomonitor. This study assessed the concentrations of mercury (Hg), cadmium (Cd), lead (Pb), and selenium (Se) in P. viridis across two key sites-a port area at the Cartagena Bay (CB) and Virgen marsh (VM) in Colombia-from 2020 to 2023. Seasonal variations driven by La Niña and El Niño phenomena significantly influenced metal concentrations, with transitional periods modulating pollutant accumulation. The levels of trace metals in soft tissue of P. viridis (dry weight) ranged from 0.0003 to 0.0039 µg/g (Cd), 0.04 to 0.21 µg/g (Hg), 0.05 to 1.18 µg/g (Pb), and 0.0029 to 0.0103 µg/g (Se). In suspended particulate matter (SPM), Cd ranged from 0.07 to 0.33 µg/g; Pb ranged from 4.94 to 25.66 µg/g; and Hg ranged from 0.18 to 1.20 µg/g. Results revealed differences in metal concentrations between sites and seasons, highlighting the role of environmental and anthropogenic factors in pollutant distribution. The findings confirm P. viridis as an effective biomonitor of complex pollution scenarios in Cartagena Bay. However, its invasive status highlights ecological risks to be addressed, such as interaction with native bivalves and benthic community structures. These results emphasize the need for ongoing monitoring efforts to mitigate pollution and preserve marine biodiversity in the Colombian Caribbean.

Human Activity as a Growing Threat to Marine Ecosystems: Plastic and Temperature Effects on the Sponge Sarcotragus spinosulus

Human activities increasingly threaten marine ecosystems through rising waste and temperatures. This study investigated the role of plastics as vectors for Vibrio bacteria and the effects of temperature on the marine sponge Sarcotragus spinosulus. Samples of plastics and sponges were collected during July, August (high-temperature period), and November (lower-temperature period). Bacterial growth and sponge responses were analysed using biochemical biomarkers. The results revealed a peak in colony-forming units (CFU), particularly of Vibrio alginolyticus, on plastics and sponges in August, followed by a decrease in November. In August, CFU counts of Vibrio spp. were significantly higher in sponges with poor external appearance (characterized by dull coloration and heavy epiphytic growth) but returned to levels observed in healthy sponges by November. Microplastics were detected in the tissues of both sponge groups, with higher concentrations found in affected specimens. Biomarker analyses revealed increased lysozyme, glutathione S-transferase, catalase, and superoxide dismutase activities in healthy sponges during August, while malondialdehyde levels, indicating oxidative damage, were higher in affected sponges. In conclusion, affected sponges exhibited elevated CFU counts of Vibrio spp. and reduced antioxidant and detoxification responses under elevated temperatures. These findings suggest that combined impacts of plastics and warming may pose significant risks to S. spinosulus in the context of global climate change.

Blood Morphology and Hematology of Adult Baikal Seals (Pusa sibirica Gmelin, 1788) Under Professional Care

Studying the blood cell morphology of marine mammals provides an opportunity to elucidate the physiological mechanisms of adaptive changes associated with the aquatic habitat that occur at the cellular level, as well as adaptations to changing environmental conditions and under various physiological and pathological processes. The Baikal seal [Pusa sibirica (family Phocidae)] is endemic to the freshwater Lake Baikal, but comprehensive hematology data are not available. We studied the morphological features of blood cells of twelve clinically normal, adult Baikal seals (n = 6 males, n = 6 females) from two oceanariums under professional care for eight years. The morphology of mature and immature erythrocytes and inclusions are described. The blood of Baikal seals is characterized by the presence of erythrocytes with a size of 8.2 ± 0.6 µm; Howell-Jolly bodies were rarely observed, the number of reticulocytes ranged from 4.1 to 93.1 × 109/L, and nucleated erythrocytes were absent. The morphological features of neutrophils, eosinophils, basophils, and platelets were described. Inter-individual and sex differences in the counts of basophils, platelets, red blood cells, and levels of hemoglobin, the mean corpuscular volume, and the mean corpuscular hemoglobin concentration were statistically observed. The results could be useful for Baikal seal veterinary care, immune response research, and comparative studies with other pinnipeds.

Active biomonitoring of river pollution using an ex-situ exposure system with two model species

In the context of increasing pollution pressure on aquatic ecosystems, it is essential to improve our knowledge of habitat quality and its suitability for organisms. It is particularly relevant to better integrate early life stages of fish into pollution biomonitoring programs, as they are reliable indicators of ecosystem integrity and because of their high sensitivity to pollutants. To avoid the influence of environmental parameters on their development, a lab-on-field approach, called the ex-situ exposure method, was developed. Aquatic organisms were exposed to a continuous flux of water under semi-controlled temperature, oxygen, and photoperiod conditions to avoid the influence of these confounding factors when interpreting the results. To investigate the potential role of water contamination, this active biomonitoring method was applied to the Garonne River (Southwest France), where migratory fish populations have declined. Two model species from different taxa were used: embryos of the Japanese medaka (Oryzias latipes) and adults of the crustacean Gammarus fossarum. The results showed a significant impact of water quality on embryo mortality and early hatching in two separate experiments on Japanese medaka. In addition, an induction of feeding rate was observed in exposed gammarids, but no impact on their embryo survival, suggesting differences in sensitivity between the two species selected. Chemical and biological analyses did not identify trace metals, pesticides, or microorganisms as potential sources of toxicity in medaka embryos or G. fossarum. These results raise concerns about the quality of the water in the Garonne River and its toxicity to aquatic organisms.

Use of multispecies (Nannochloropsis oceanica, Artemia franciscana, and Arbacia nigra) approach to assess the quality of marine water from Callao Bay, Peru

Multi-species tests in bioassays offer a holistic view of the ecosystem's response to toxicity, as different species display varying sensitivities to pollutants. This research aimed to assess the ability of toxicity tests' to distinguish contamination levels, examine site-specific effects, and investigate seasonal variability. Using a multispecies approach (Nannochloropsis oceanica, Artemia franciscana, and Arbacia nigra), bioassays evaluated marine water quality from Callao Bay in Peru across four sampling areas (Naval School: PA1, Peruvian Marine Institute: PA2, Callao Pier: PA3, and San Lorenzo Island: PA4). These species, with varying sizes and morphologies, are relevant to marine systems and ideal for multispecies toxicity testing, contributing to broader environmental impact discussions. To conduct toxicity bioassays, seasonal evaluations were performed in fall, winter, spring, and summer. Brine shrimp displayed seasonal variations in toxicity values, with notable mortality rates during winter. Nannochloropsis oceanica was the most sensitive species, showing moderate toxicity across seasons. Areas impacted by pollution sources, such as wastewater and maritime traffic, exhibited the highest toxicity levels (PA3 and PA4). These fluctuations underscore the need to consider seasonal and local conditions when assessing organism sensitivity to seawater contaminants. Additionally, they reveal the complex interplay between environmental factors, water quality, and organism responses in marine ecosystems.

Differential biotransformation ability may alter fish biodiversity in polluted waters

Divergence in the activity of biotransformation pathways could lead to species sensitivity differences to chemical stress. To explore this hypothesis, we evaluated the biotransformation capacity of five fish species representative of Swiss biodiversity assemblages across watercourses surrounded by different land use. We report interspecific differences regarding the presence and activity of major biotransformation pathways, such as the invasive pumpinkseed (Lepomis gibbosus) displaying micropollutant clearance between 3- and 7-fold higher than native species (e.g. Salmo trutta, Squalius cephalus) collected in the same areas. These differences were exacerbated by urban and agricultural influence, which increased biotransformation potential at the enzyme level by approximately 11-fold and micropollutant clearance by approximately 2-fold compared to fish from areas with minimal human influence. In the context of the chemical defensome, we argue that fish with low biotransformation activity carry a greater burden on chemical stress, making them less likely to cope with additional stressors and sustain their population in competition with species with a higher biotransformation capacity, thus causing alterations to biodiversity assemblages.

A repercussion of COVID-19 lockdown on water quality along the east coast of India

The COVID-19 pandemic and subsequent lockdown measures significantly impacted various sectors, including coastal environments. While restrictions led to temporary improvements in air quality, their effects on coastal waters remained understudy. This research conducted four cruises along the east coast of India during pre- and post-COVID-19 lockdown to assess the water quality changes. Results show a significant increase in Chl-a (31.8%), DO (28.1%), and SDD (7.7%), while reductions in NO3 (34.7%), PO4 (51.7%), SiO4 (16.2%), TSM (25.4%), TC (72.3%), and FC (83.3%) were observed. Multivariate analysis identified land-based pollution as the primary source of pollution in coastal waters. Overall, the findings suggest improved coastal water quality during the lockdown. However, for the sustainability of coastal waters, it is proposed that raw sewage, wastewater, and atmospheric fluxes affecting coastal water quality must be regulated.

Dynamics of antibiotic resistance genes and bacterial community structure within substrate biofilms

Biofilms that develop on the surface of substrates are critical for treating wastewater. The accumulation of antibiotic resistance genes (ARGs) within these biofilms is particularly noteworthy. Despite their importance, studies that focus on biofilms attached to substrate surfaces remain scarce. This investigation explored the prevalence and succession of ARGs and microbial dynamics in biofilms on different substrates (ceramic, biomass filter, and steel slag) versus water biofilms over a year. Results showed distinct differences in ARG profiles between water and substrate biofilms. Multidrug ARGs constituted 39.14-46.73% of all ARGs in the substrate biofilms, with macrolide ARGs making up 11.98-14.52%. Seasonal variations influenced the diversity of the ARGs, notably increasing during the spring. The neutral community model suggested that the ARG assembly was dominantly driven by stochastic process. Proteobacteria, Actinobacteria and Campylobacter emerged as the predominant phyla within these biofilms. The microbial community distribution was predominantly influenced by ammonium nitrogen (NH4+-N) (R2 = 0.4113), temperature and total nitrogen (TN). Notably, temperature exerted a critical impact on the microbial community distribution (P = 0.001), identifying it as the principal factor for spatial arrangement. Furthermore, the structural variations of ARGs were primarily driven by total organic carbon (TOC) (R2 = 0.3988), temperature, oxidation-reduction potential (ORP) and NH4+-N. Our findings provided new insights into the optimization of substrate selection and ecological management to manage ARG enrichment, offering a promising strategy for aquatic ecological restoration and pollution control.

Heavy metals and microplastics derived from laboratory effluents enhance toxicological risks to the ecosystems of canals in Bangladesh

The occurrence of chemical effluents in different water bodies is an emerging concern. However, the effect of laboratory effluents on the canal ecosystem in Bangladesh is largely unknown. In this study, we collected 10 components of the canal ecosystem including sediments, water, fish, crabs, snails, phytoplanktons, and weeds specifically from canals that directly receive laboratory effluents. We examined the occurrence of both the essential (Fe, Mn, Cu, and Zn) and toxic (Pb, Cd, Cr, Co, Ni, and As) metals as well as microplastics (MPs). Results explored that laboratory effluents strongly interact with the components of the canal ecosystem and enhance the abundance of toxic metals in the canal hydrosystem. Furthermore, diverse types of MPs including fibers, fragments, and microbeads were observed in all components of the canal ecosystem. Remarkably, our results unveiled that the co-occurrence of pollutants was more severe in benthic organisms like snails or crabs might be due to their omnivorous food habits. The cumulative pollutant accumulation was much higher in all components of the canal ecosystem indicating a greater ecological risk. Although the potential risk index (RI) or hazardous index (HI) from fish ingestion was found within acceptable limits, the biomagnification of pollutants due to repeated ingestions may have strong ecotoxicological impacts even at very low concentrations.

Quantifying the Interactions and Cumulative Effects of Multiple Stressors on Salmonids

The cumulative effects of human activities and natural pressures pose significant threats to ecosystem functioning and global biodiversity. Assessing the cumulative impact of multiple stressors-whether acting simultaneously or sequentially and directly or indirectly-is challenging due to their complex interactions. Consequently, these interactions may be unintentionally overlooked or disregarded in management decisions. While existing reviews have focused on coastal and freshwater ecosystems, analyses specifically targeting salmonids as a focal group are lacking. This research presents the first quantitative and qualitative assessment of stressor interactions affecting salmonid biology and physiology. A focused literature search identified 118 experimental trials with multiple stressors on salmonids. From these, 46 cases were considered suitable for the quantitative analysis. We calculated Hedges' g effect sizes to classify the interactions between multiple stressors as additive, synergistic, or antagonistic. Our findings revealed that additive effects were found most frequently (50% of interactions), followed by synergistic (30.5%) and antagonistic (19.5%) interactions. Additionally, we performed a network analysis including cases focusing on the influences of multiple stressors interactions (n = 38). Our qualitative analysis identified temperature, metals, and pesticides as the most paired stressors across the three types of interactions. The findings of this research highlight the potential vulnerabilities of salmonids and their habitats by identifying key interactions between multiple stressors, and priorities for future research. Understanding these interactions and cumulative effects, particularly in the context of climate change, can inform targeted conservation and management strategies, contributing to the preservation of these important fish species and their ecosystems, which are vital to local human communities.

Fishery and ecology-related knowledge about plants among fishing communities along Laguna Lake, Philippines

BACKGROUND

Ethnobotanical knowledge about plant roles in fisheries is crucial for sustainable resource management. Local ecological knowledge helps understand dynamics of the lake ecosystem. Fishers use plants based on availability and characteristics while adapting to the changes in the environment. Studying fishery related uses of plants and algae and the challenges interconnected with them from local perspectives can provide insights into their beneficial uses and impacts to the ecosystem.

METHODS

The study investigates the botanical knowledge of three fishing villages in Laguna Lake or Laguna de Bay (LB), Philippines, including Buhangin, Sampiruhan, and Mabato-Azufre, each with varying degrees of industrialization. The ethnobotanical study, which gathered 27 interviews between June 2022 and July 2024, included plant collection with the help of local collaborators, including local fishers as research guides.

RESULTS

Fishers in LB highlighted positive and negative plant-fishing interactions. The most frequently mentioned plant applications were fish habitat and fish hiding places. Fish food, spawning sites, conservation, and a number of challenges such as navigational concerns and aquaculture fish deaths had been previously reported in local use reports. The remaining observations provide new insights into plant-fishing interactions, including indicators of food quality and food sources for fish, the decrease in the action of waves, and how plants help in improving the quality of the water.

CONCLUSION

These results highlight that the knowledge of fishers regarding the ecosystem in which they conduct their fishing activities provides baseline information about the positive and negative relationships between plants and fishing activities in the region, which is vital for further understanding its biodiversity and ecosystem interactions. It is crucial to consider fisher knowledge and involve them as equal partners in conservation efforts of LB.

A multiple biomarker approach to understand the effects of microplastics on the health status of European seabass farmed in earthen ponds on the NE Atlantic coast

The occurrence of microplastics (MPs) in aquaculture environments is a growing concern due to their potential negative effects on fish health and, ultimately, on seafood safety. Earthen pond aquaculture, a prevalent aquaculture system worldwide, is typically located in coastal and estuarine areas thus vulnerable to MP contamination. The present study investigated the possible relation between MP levels of European seabass (Dicentrarchus labrax) farmed in an earthen pond and its health status. More precisely, two groups of fish were established based on the lowest and highest number of MPs found collectively in their gastrointestinal tract (GIT), liver, and dorsal muscle: fish with ≤2 MP/g and fish with ≥4 MP/g. The intestinal integrity and oxidative stress biomarkers in the liver and dorsal muscle were evaluated in the established groups. No significant differences in the biometric and organosomatic parameters between groups were observed. The results indicated a significant increase in the number of acid goblet cells (GC) in the rectum of fish with higher MP levels (p = 0.016). Increased acid GC number may constitute a first defence strategy against foreign particles to protect the intestinal epithelium. No significant differences in oxidative stress biomarkers between the two fish groups were observed, namely in the activity of superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase in the liver, or in lipid peroxidation levels in the liver and dorsal muscle. The overall results suggest that MP levels were possibly related to an intestinal response but its potential implications on the health status of pond-farmed seabass warrant further investigation. Monitoring MP occurrence across stages of aquaculture production could help to elucidate the potential threats of MPs to fish health.

Effects of mifepristone, a model compound with anti-progestogenic activity, on the reproduction of African clawed frog (Xenopus laevis)

This is the first study on how a substance with anti-progestogenic activity affects amphibian reproduction. Mifepristone, a synthetic anti-progestin used in abortion pills, was chosen as model compound. African clawed frog (Xenopus laevis) females were exposed to four mifepristone concentrations (0.7, 9, 120, and 1380 ng∙L-1) for 30 days. A control group was also included. Egg-laying during the experiment was significantly less at the highest concentration. At the experiment's end, mifepristone-exposed and control females were randomly mated with sexually mature males. Breeding rate for females exposed to 1380 ng∙L-1 mifepristone was only 50 %. Histology revealed no significant changes in gonads, thyroid, or liver. Females exposed to 1380 ng∙L-1 mifepristone had lower estradiol levels in plasma, lower mRNA expression of lh and fsh in brain-pituitary complex, and p450scc in ovaries. In liver, mRNA level of npr was significantly increased in females exposed to 120 ng∙L-1 mifepristone. mRNA expression of mpr, erβ, dio2, and dio3 were upregulated in animals exposed to 9 ng∙L-1 and 120 ng∙L-1 mifepristone, whereas vtg expression was significantly downregulated in females exposed to 1380 ng∙L-1 mifepristone. All these findings show that exposure to compounds with anti-progestogenic activity affects the hypothalamus-pituitary-gonad axis and decreases reproductive success.

Composition and distribution of the near-shore waters bordering the coral reefs of Aruba, Bonaire, and Curaçao in the Southern Caribbean

This study aimed to identify ocean- and land-based sources of nutrients to the coral reef communities surrounding the Southern Caribbean islands Aruba, Bonaire, and Curaçao (ABC islands). The composition of water masses around these islands were assessed to depths up to 300 m and three distinct overlying water masses were identified, separated by mixing zones. A fluctuating pycnocline separating surface from deeper (>∼50 m) water indicated the presence of internal waves. Nutrient profiles were typical of tropical waters with oligotrophic waters occurring above the pycnocline and a deep chlorophyll-a maximum (DCM) just below it (∼65 m). Concentrations of dissolved nutrients differed among islands. Inorganic nitrogen (DIN) and phosphate concentrations were respectively lowest around Bonaire and Curaçao. The spatial distribution of chlorophyll-a (indicative of phytoplankton biomass), rather than nutrient concentrations, suggested the presence of higher-than-average nutrient concentrations in islands with higher population densities and near urbanized/industrial areas.

How to deal with xenobiotic compounds through environment friendly approach?

Every year, a huge amount of lethal compounds, such as synthetic dyes, pesticides, pharmaceuticals, hydrocarbons, etc. are mass produced worldwide, which negatively affect soil, air, and water quality. At present, pesticides are used very frequently to meet the requirements of modernized agriculture. The Food and Agriculture Organization of the United Nations (FAO) estimates that food production will increase by 80% by 2050 to keep up with the growing population, consequently pesticides will continue to play a role in agriculture. However, improper handling of these highly persistent chemicals leads to pollution of the environment and accumulation in food chain. These effects necessitate the development of technologies to eliminate or degrade these pollutants. Degradation of these compounds by physical and chemical processes is expensive and usually results in secondary compounds with higher toxicity. The biological strategies proposed for the degradation of these compounds are both cost-effective and eco-friendly. Microbes play an imperative role in the degradation of xenobiotic compounds that have toxic effects on the environment. This review on the fate of xenobiotic compounds in the environment presents cutting-edge insights and novel contributions in different fields. Microbial community dynamics in water bodies, genetic modification for enhanced pesticide degradation and the use of fungi for pharmaceutical removal, white-rot fungi's versatile ligninolytic enzymes and biodegradation potential are highlighted. Here we emphasize the factors influencing bioremediation, such as microbial interactions and carbon catabolism repression, along with a nuanced view of challenges and limitations. Overall, this review provides a comprehensive perspective on the bioremediation strategies.

Developing behavioural ecotoxicology assessment methods in the tropical marine amphipod, Parhyale hawaiensis: A study with benzo[a]pyrene (BaP)

Toxicant-induced behavioural changes provide important insights into environmental toxicity, particularly in vulnerable tropical marine habitats. However, ecotoxicological knowledge of organisms in these environments is insufficient. We aimed to develop innovative and cost-effective ecotoxicology methods using Parhyale hawaiensis as a tropical model organism. Adult P. hawaiensis were exposed to aqueous benzo[a]pyrene (BaP) (2 μM) and dietary BaP (50, 250, or 1250 μg BaP/g diet). Survival (24 to 96 h) and behavioural responses (21d) to foraging, reproduction, and predator avoidance were studied. Aqueous and dietary exposures to benzo[a]pyrene (BaP) did not affect survival but induced significant immobility with effective concentration (EC50 ± SE, 96 h at 11.89 ± 1.19 μM). Relative to the control group, aqueous exposure to 2 μM and dietary exposure to 250 and 1250 μg BaP/g feed resulted in statistically significant behavioural changes. These included a 55-76 % reduction in feeding rates, 133 % increase in chemosensation time, 60-122 % drop in moulting frequency, 200 % delay in precopulatory activity, 50-83 % decrease in geotactic activity, and 300-400 % increase in phototactic activity (all significant at p ≤ 0.05). The methods developed in this study are cost-effective, sensitive, and readily integrated into other endpoint analyses, reinforcing the potential of P. hawaiensis as a tropical ecotoxicology model for detecting toxicant-induced behavioural responses and enhancing marine risk assessments.

COVID-19 induced lockdown reduced metal concentration in the surface water and bottom sediment of Asia's largest lagoon

COVID-19 (hereafter COVID) induced lockdown provided a unique opportunity to evaluate the effects of human activities on coastal ecosystems. This study quantified the seasonal variations in concentrations of nine metals (Al, Cr, Cd, Co, Cu, Fe, Mn, Ni, and Pb) in surface water and sediment samples of the largest brackish water lagoon in Asia (i.e., Chilika Lagoon), comparing pre-and post-COVID scenarios. The COVID lockdown resulted in a wide variation in metals concentrations, with surface water showing 1 to 8.6-fold reduction in metals such as Al, Cr, Cu, Fe, Mn, and Pb, while sediment displayed a more modest reduction of 1 to 1.3-fold. Metals like Cd, Co and Ni were below detection limit in post-COVID water samples with a slight decrease (1-fold) in the sediments. COVID lockdown did not show any significant correlation with metal concentrations in water or sediment. This study provides baseline data for metal contamination in the surface water and sediment of the Chilika Lagoon.

Nutrient variations and environmental relationships of lakes and reservoirs before and after the COVID-19 epidemic public lockdown policy elimination: A nationwide comparative view in China

The continuous impact of COVID-19 on aquatic environments has attracted considerable attention, primarily focusing on short-term water quality effects during lockdown, while studies on changes following the lifting of restrictions are relatively limited. Following adjustments to China's pandemic public policy in December 2022, the effects on water quality and nutrient status in lakes and reservoirs remain unclear. In this study, we collected national environmental monitoring data comprising 15 indicators of water quality, meteorology, soil, and economic factors, from 86 lakes and reservoirs across China between March 2021 and December 2023. Total nitrogen (TN), total phosphorus (TP), the mass TN/TP ratio (TN/TP), and ammonia-nitrogen (NH3-N) were selected as representative nutrient indicators. The water quality index (WQI) and multivariate statistical techniques were employed to comprehensively assess national water quality and identify the drivers of nutrient variations in sub-regions. The results show that during the monitoring period from 2021 to 2023, Chinese national water quality consistently fell within the 'good (61-80)' or 'excellent (81-100)' categories, with the lowest water quality observed in the summer of each year. The summer of 2021 recorded the lowest WQI value among all seasons at 75.01. Following the elimination of the COVID-19 epidemic public lockdown policy, concentrations of TN, TP, and NH3-N declined. These findings indicate a general improvement in the water quality of lakes and reservoirs nationwide. Mantel test and multiple stepwise linear regression models revealed significant correlations between nutrients and human activity indicators in central, eastern, and northern China. In northern China, TP showed a significant positive correlation with GDP (0.2 < Mantel's r < 0.5, P < 0.05), with the beta value increasing from 0.27 to 0.38 after the elimination of the COVID-19 epidemic public lockdown policy. In these regions, the influence of rainfall, wind speed, NDVI, surface soil moisture, and water temperature on nutrients shifted from significant to insignificant effects after the elimination of the COVID-19 epidemic public lockdown policy, indicating that human activities have overshadowed natural factors. This study examines the water quality and nutrient status of lakes and reservoirs in China after the elimination of the COVID-19 epidemic public lockdown policy, highlighting the long-term impacts and spatial variations of the pandemic. These findings will inform environmental governance and promote sustainable water resource management in the post-pandemic era.

Purification Resistance Index: A new water quality assessment method toward drinking water production

Water quality assessment plays a significant role in ensuring the availability of clean and safe water. The Water Quality Index (WQI) model method has been developed to provide a basis for assessing water quality by integrating various water quality parameters. However, existing WQIs do not "actively" consider the difficulty of water treatment from raw water to specific water use scenarios. This study proposes a novel model framework, named as Purification Resistance Index (PRI), quantitatively evaluating not only the exceedance of pollutants but also how difficult they can be removed in the water treatment process. The framework is built based on the conventional drinking water treatment processes, with sub-indices for coagulation-sedimentation (rc), filtration (rf), disinfection (rd), and advanced treatment (ra). The model considers appropriate weights assigned to each sub-index to calculate the purification resistance, resulting in a comprehensive index for water quality evaluation. Case studies on nationwide and citywide water source reservoirs demonstrated the applicability of PRI approach. PRI breakthrough the traditional water quality risk assessment paradigm and extents to engineering region and provide useful tools for water source supervision, drinking water treatment plant planning and updating, operation control, and other purposes. Water authority, water utility and municipal design institute will all benefit. It is open for more localized practices validation and discussion.

Comparative Seasonal Trends and Potential Health Impacts of Arsenic and Chromium in Surface Water after Adsorption Using Highly Dispersed Fe3O4 Nanoparticles

Surface water from springs, rivers, and dams is often used as an unconventional drinking water source in rural areas where potable water is often unavailable. However, this practice carries significant health risks due to potential contaminants. In this study, the concentrations of arsenic (As) and chromium (Cr) were assessed seasonally using graphite furnace atomic absorption spectrometry (GFAAS). Highly dispersed Fe3O4 nanoparticles were synthesized, characterized, and utilized as adsorbents to remove As and Cr ions from various water matrices. The removal process was optimized by adjusting the mass of the nanoparticles, pH levels, and sonication time. To further understand the adsorption process, adsorption isotherms and kinetics were conducted. Physicochemical properties such as pH, electrical conductivity, and total dissolved solids were seasonally evaluated. The average As concentrations were in the range of 13.3-46.8 µg/L, while Cr was in the range of 1.02-5.04 µg/L. Expectedly, higher concentrations of As and Cr were observed in summer when there was intense precipitation, and the lowest concentrations were observed in winter, with little to no precipitation. The calibrated GFAAS displayed an excellent limit of detection, limit of quantification, and linearity of 0.092-0.13, 0.27-0.34, and 0.27-70 µg/L for As, while 0.031-0.07, 0.16-0.21, and 0.16-70 µg/L were attained for Cr, respectively. Arsenic levels exceeded 10 µg/L in all seasons, indicating that these concentrations were above the maximum permitted levels set by the World Health Organization and the South African National Standards. According to the health risk assessment, high As concentrations were alarming, as they were seasonally increasing, with the chronic daily intake exceeding the oral reference dose, whilst the incremental lifetime cancer risk was significantly high.

Assessing the risk of consuming fish from Kanyakumari (Tamil Nadu), India: An evaluative study on bioaccumulated heavy metals in different fish species using inductively coupled plasma mass spectrometry

Environmental pollutants which are developing an alarming situation in the contemporary world captured attention in the present research. When it comes to food safety and security concerns it becomes an important field to be studied rigorously as food contributes majorly to human and animal health. The pollution of aquatic ecosystems by heavy metals (HMs) ultimately results in adverse effect on the food chain, which is covered in the current study. Fish is considered to be one of the main components of a balanced diet plate due to its high-quality protein, which sets it apart from other dietary sources. On the other hand, it is also susceptible to the absorption and bioaccumulation of HMs at toxic levels. In our study, we have considered three different species (Nemipterus japonicus, Oreochromis mossambicus, and Lates calcarifer) of fish collected from Kanyakumari, Tamil Nadu (India). Three organs namely liver, gill, and muscle were taken into consideration for the HM profiling using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The Arsenic (As), Cadmium (Cd), Chromium (Cr), Mercury (Hg) and Lead (Pb) were found to be in varied concentrations ranging from 0.1 to 1.13, 0.89-1.45, 9.95-30.66, 0.14-1.62, and 24.69-189.5 µg/kg respectively, in the studied organs of fish. Carcinogenic and noncarcinogenic risk assessments were also done indicating a notable level of Pb and Cr in selected fish species. The Hazard Index (HI) for Oreochromis mossambicus was >1 for adults and children, indicating future possibility of probable health hazards on daily consumption of these fish. In Oreochromis mossambicus, the cancer risk (CR) values for Cr and As were significantly high, particularly for children, indicating a possible occurrence of acute health risk as it exceeded the threshold of 1 × 10-3 and suggesting a significant concern. Though consumption of fish on daily basis in such significant quantity is practically impossible both for adult and children, rendering these species safe.

Marine mesocosm system: A reliable tool for testing bioaccumulation and effects of seawater enrichment with dissolved iron in reef organisms

In 2015, a marine mesocosm facility was designed and implemented by the Coral Vivo Project in its research station (Porto Seguro, Bahia State, Brazil) to initially study the effects of global impacts, especially ocean warming and acidification, on coral reefs. However, local impacts, including seawater contamination with metal(loid)s, are considered as a major threat to coral reefs. Also, in 2015, the largest disaster involving a mining dam occurred in Brazil. Iron (Fe) mining tailings originated from the dam failure affected not only freshwater ecosystems (rivers, lakes and lagoons), but also adjacent beaches, mangroves, restingas, reefs and other marine systems. Seawater, sediments and biota were contaminated with metal(loid)s, especially Fe, arsenic (As), mercury (Hg) and manganese (Mn). Therefore, we aimed to adapt the marine mesocosm facility of the Coral Vivo Project to evaluate the bioaccumulation and biological impacts of increasing concentrations of dissolved Fe on a diversity of reef organisms. Results obtained indicate a great versatility and reliability of the marine mesocosm system for application in biological and ecological studies on the isolated effect of seawater dissolved Fe on reef organisms of different functional groups simultaneously.•Studies involving seawater enrichment with dissolved Fe can be performed using a marine mesocosm system.•The marine mesocosm is a reliable tool to study the isolated effects of metal(loid)s on reef organisms.

Dyeing waters: Does indiscriminate dye use threaten aquatic ecosystems?

Aquatic ecosystem conservation is imperative to reaching global biodiversity and sustainability targets. However, the ecological status of waters has been continuously eroded through mismanagement in the face of existing and emerging anthropogenic stressors, such as pollutants. There has been an emerging trend towards the use of dyes to manage algae and plants as well as to alter aesthetics within various aquatic environments. This artificial colouring has potential ecological implications through reductions in light levels and disruptions to thermoclines (i.e., temperature regime changes with depth). Abiotic regime shifts could in turn drive ecological cascades by depowering primary production, hampering top-down trophic interactions, and affecting evolved animal behaviours. Despite commercial dyes being marketed as acutely non-toxic, very little is known about the chronic effects of these dyes across ecological scales and contexts. We thus call for greater research efforts to understand the ecological consequences of dye usage in aquatic environments, as well as the socio-cultural drivers for its application. This emerging research area could harness approaches such as biological assays, community module experiments, remote sensing, culturomics, and social surveys to elucidate dye effects, trends, and perspectives under a pollution framework. A greater understanding of the potential effects of dye in aquatic ecosystems under relevant contexts would help to inform management decisions and regulation options, while helping to mediate ecocentric and anthropocentric perspectives.

Deciphering the functional assembly of microbial communities driven by heavy metals in the tidal soils of Hangzhou Bay

Understanding the interaction between heavy metals and soil microbiomes is essential for maintaining ecosystem health and functionality in the face of persistent human-induced challenges. This study investigated the complex relationships between heavy metal contamination and the functional characteristics of soil microbial communities in the tidal soils of Hangzhou Bay, a region experiencing substantial environmental pressure due to its proximity to densely populated and industrialized regions. The north-shore sampling site showed moderate contaminations (mg/kg) of total arsenic (16.61 ± 1.13), cadmium (0.3 ± 0.05), copper (31.28 ± 1.23), nickel (37.44 ± 2.74), lead (34.29 ± 5.99), and zinc (120.8 ± 5.96), which are 1.29-2.94 times higher than the geochemical background values in Hangzhou Bay and adjacent areas. In contrast, the south-shore sampling site showed slightly higher levels of total arsenic (13.76 ± 1.35) and cadmium (0.13 ± 0.02) than the background values. Utilizing metagenomic sequencing, we decoded microbial functional genes essential for nitrogen, phosphorus, sulfur, and methane biogeochemical cycles. Although soil available nickel content was relatively low at 1 mg/kg, it exhibited strong associations with diverse microbial genes and biogeochemical pathways. Four key genes-hxlB, glpX, opd, and phny-emerged as pivotal players in the interactions with available nickel, suggesting the adaptability of microbial metabolic responses to heavy metal. Additionally, microbial genera such as Gemmatimonas and Ilumatobacter, which harbored diverse functional genes, demonstrated potential interactions with soil nickel. These findings highlight the importance of understanding heavy metal-soil microbiome dynamics for effective environmental management strategies in the tidal soils of Hangzhou Bay, with the goal of preserving ecosystem health and functionality amidst ongoing anthropogenic challenges.

Biodegradation of used engine oil by lead-resistant bacteria Acinetobacter sp.HAR20 newly isolated from harbour seawater (Oran, Algeria)

This paper focuses on the degrading capacity of various hydrocarbon fractions of used engine oils (UEO) by marine microorganisms, as well as the biosorption of heavy metals. A bacterial strain with a significant capability to grow on UEO as a sole source of carbon and energy was isolated from harbour seawater samples (Oran, Algeria). The molecular identification by sequencing the 16S rDNA gene revealed that the bacterium matched Acinetobacter baumanii with 96.84% homology similarity. Thus, strain HAR20 was named Acinetobacter sp.HAR20. The degradation rate of UEO (at 1%, v/v) obtained after 15 days of incubation was about 53.4 ± 4.2%. The results of GC-MS analysis of the biodegraded residual motor oil indicate that strain Acinetobacter sp.HAR20 degrades alkanes with chain lengths ranging from C4 to C48 completely or to shorter fractions. The bacterium was also able to degrade all aromatic compounds of UEO, including polycyclic aromatic hydrocarbons (alkylated and no alkylated naphthalene, alkylated phenanthrene, and fluorene). The strain Acinetobacter sp.HAR20 exhibited different degrees of resistance to the heavy metals tested (Cd, Zn, Ni, Cu, Fe, and Pb). The highest tolerance was obtained for Pb (600 mg.l-1). The study of lead biosorption at a concentration of 300 mg.l-1 revealed that the bacterium displayed a removal rate of 57.47 ± 7.5%. The strain Acinetobacter sp.HAR20 has shown an interesting biodegradation potential; therefore, it could be proposed as a choice for the bioremediation of contaminated seawater by used engine oils.

Host-associated microbes mitigate the negative impacts of aquatic pollution

Pollution can negatively impact aquatic ecosystems, aquaculture operations, and recreational water quality. Many aquatic microbes can sequester or degrade pollutants and have been utilized for bioremediation. While planktonic and benthic microbes are well-studied, host-associated microbes likely play an important role in mitigating the negative impacts of aquatic pollution and represent an unrealized source of microbial potential. For example, aquatic organisms that thrive in highly polluted environments or concentrate pollutants may have microbiomes adapted to these selective pressures. Understanding microbe-pollutant interactions in sensitive and valuable species could help protect human well-being and improve ecosystem resilience. Investigating these interactions using appropriate experimental systems and overcoming methodological challenges will present novel opportunities to protect and improve aquatic systems. In this perspective, we review examples of how microbes could mitigate negative impacts of aquatic pollution, outline target study systems, discuss challenges of advancing this field, and outline implications in the face of global changes.

Effects of urban streams on muscle non-protein thiols, gill and liver histopathology in zebrafish (Danio rerio) assessed by active biomonitoring

Aquatic biota are exposed to toxic substances resulting from human activities, reducing environmental quality and can compromise the health of the organisms. This study aimed to employ Danio rerio as an environmental bioindicator, analyzing the effects of water from distinct urban aquatic environments. An active biomonitoring system was set up to compare the temporal dynamics of histological biomarkers for gill and liver and the patterns of non-protein thiols (NPSH) in muscle in specimens exposed for 3, 6, and 12 days. Three large urban basins in the city of Campo Grande (Midwest of Brazil) were selected. Two sites are in a very populous area (i.e Lagoa and Bandeira) and another on in an area with agricultural activities (i.e Anhanduí). All the streams displayed distinct qualitative characteristics. The presence of metals, including Mn, Zn, Fe, and Al, as well as pH, temperature, and dissolved oxygen, accounted for 38% of the variability (PC1), while total solids, conductivity, ammonia, nitrite, and explained 24 % (PC2). Degree tissue changes index (DTC) in gill and the concentration of NPSH increased in all streams during 3, 6 and 12 days of exposure. DTC in liver increases in all exposure times in most populous stream (i.e Lagoa and Bandeira). Histopathological evidence in the gill, including proliferation, desquamation, and necrosis of the primary lamellar epithelium; fusion and aneurysms in the secondary lamellar epithelium were observed after three days of exposure. Degenerative nuclear figures were noted in the liver after three days of exposure, followed by hepatocellular hypertrophy, lipidosis, and necrosis at twelve days. Our findings showing time-dependent effects of urban aquatic environments in histopathological (i.e DTC) and biochemical biomarkers in zebrafish. The biomonitoring model enabled a comparison of the temporal dynamics of various health markers, using zebrafish as bioindicator. Future studies might use this experimental model and biomarkers for environmental biomonitoring program.

Anthropogenic activity shapes the assemble and co-occurrence pattern of microbial communities in fishing harbors around the Bohai economic circle

This study aimed to elucidate the effects of coastal environmental stress on the composition of sediment bacterial communities and their cooccurrence patterns in fishing harbors around the Bohai Economic Circle, China. Compared with the natural sea area, fishing harbors contained higher levels of organic pollution (organic pollution index = 0.12 ± 0.026) and considerably reduced bacterial richness and evenness. The distributions of sediment microbial communities clustered along the pollutant concentration gradients across fishing harbors. Betaproteobacteria dominated (76%) organically polluted fishing harbors, which were mostly disturbed by anthropogenic activities. However, the harbors also revealed the absence of numerous pathogenic (Coxiella and Legionella) and photosynthetic (Synechococcus and Leptolyngbya) bacteria. Abundant genera, including Thiobacillus and Arenimonas, exhibited a positive correlation with total phosphorus and a negative correlation with total nitrogen in sediments. Meanwhile, Sulfurovum, Psychrobacter, and Woeseia showed the opposite trend. Pollutant accumulation and anthropogenic activities caused the decrease in the sediment microbial diversity and dispersal ability and promoted convergent evolution. Severely polluted harbors with simplified cooccurrence networks revealed the presence of destabilized microbial communities. In addition, the modularity of bacterial networks decreased with organic pollution. Our results provide important insights into the adjustment mechanism of microbial communities to community organization and functions under environmental pollution stress. Overall, this study enhanced our understanding of how microbial communities in coastal sediments adapted and survived amidst anthropogenic activities like oily effluent discharges from large ships, wash water, domestic sewage, garbage, and fisheries wastes. It also examined their resilience to future contamination.

Plastic nests: The first record of the Yellow-rumped Cacique (Cacicus cela) and the Great Kiskadee (Pitangus sulphuratus) building nests with discarded fishing material on the Amazon Coast

The Amazonian coastal ecosystems face a significant threat from plastic contamination, posing a major risk to their biodiversity. Here, we provide the first evidence of using plastics in nest building by Yellow-cacique Cacique (Cacicus cela) and Greater Kiskadee (Pitangus sulphuratus). During 2023 and 2024, 15 nests built with ropes and fishing lines were recorded in the Brazilian Amazon Coast, a colony of 12 nests in the State of Amapá and one nest in Pará for C. cela, and one nest for P. sulphuratus was observed in Maranhão during the fieldwork, covering all Brazilian Amazon Coast. These nests were observed on the edge of mangroves, built with solid waste from fishing activities, pointing out how environmental pollution can be incorporated into wildlife this issue. Our records emphasize the effect of plastic pollution on two passerine species associated with mangrove forests and the need for conservation measures and further research.

Water quality assessment of Upper Ganga and Yamuna river systems during COVID-19 pandemic-induced lockdown: imprints of river rejuvenation

Clean river water is an essential and life-sustaining asset for all living organisms. The upper Ganga and Yamuna river system has shown signs of rejuvenation and tremendous improvement in the water quality following the nationwide lockdown due to the coronavirus pandemic. All the industrial and commercial activity was shut down, and there was negligible wastewater discharge from the industries. This article addresses the water quality assessment from the study area, which is based on the original data of physical parameters, major and trace elements, and stable isotopes (hydrogen and oxygen) systematics during the nationwide lockdown. The impact of the lockdown could be seen in terms of an increase in dissolved oxygen (DO). Water samples were collected from the Upper Ganga and Yamuna river basins (Alaknanda, Bhagirathi, and Tons rivers) during an eight-week lockdown in Uttarakhand, India. We discussed the signs of rejuvenation of riverine based on physical parameters, major ions, trace elements, isotopic ratios, and water pollution index (WPI). Results reveal that the water quality of the entire upper basins of the Ganga has significantly improved by 93%, reflecting the signs of self-rejuvenation of the rivers. Multivariate analysis suggests a negative factor loading for an anthropogenic element (NO 3 - ), implying that they contribute little to the river water during the lockdown. Further, bicarbonate (HCO 3 - ) is a dominant element in both river basins. The geochemical facies are mainly characterized by the (Ca 2 + : Mg 2 + : H C O 3 - ) type of water, suggesting that silicate rock weathering dominates with little influence from carbonate weathering in the area. The positive factor loadings of some cations, likeHCO 3 - ,Ca 2 + , andMg 2 + reflect their strong association with the source of origin in the lockdown phases. Stable isotopic reveals that the glaciated region contributed the most to the river basin, as evidenced by the low d-excess in riverine water compared to anthropogenic contributions. Rivers can self-rejuvenate if issues of human influence and anthropogenic activities are adequately resolved and underline our responsibility for purifying the ecosystem. We observed that this improvement in the river water quality will take a shorter time, and quality will deteriorate again when commercial and industrial activity resumes.