Freshwater Water Research Articles

UPAYA KONSERVASI IKAN BETTA CF. CRASENS DI BANGKA BARAT MELALUI ANALISIS MORFOMETRIK DAN MERISTIK

The Bangka Belitung Archipelago is rich in biodiversity, including endemic fish such as Betta cf. crasens, commonly known as "Tepalak" or "Tempalak." This study aims to identify the morphological, morphometric, and meristic characteristics of Betta cf. crasens as a preliminary step for domestication and conservation of local species. Samples were collected from the freshwater waters of Jebus, Bangka Barat, using a quantitative descriptive method. Results showed that this fish has a compressed body shape, terminal mouth, and pointed tail fin. Morphometric measurements included 15 characteristics, with an average total length of 5.75 mm. Meristic analysis revealed fin ray formulas, including C.XIII for the tail fin and D.VIII for the dorsal fin. These findings provide a critical foundation for the sustainable management of Betta cf. crasens and further research development.

Spatio-Temporal Analysis of Water Hyacinth Density (Eichhornia crassipes) in Lake Rawa Pening 2019 - 2023 Using NDVI Algorithm on Google Earth Engine (GEE)

Abstract Water hyacinth (Eichhornia crassipes) is an aquatic plant that floats in freshwater waters that has the ability to grow very fast and is invasive. This plant is able to reproduce vegetatively and generatively and is able to double its population within two weeks so that it can endanger the ecosystem in the waters. The purpose of this research is to map the distribution pattern, dynamics of changes in vegetation density and changes in water hyacinth area with spatial-temporal techniques using remote sensing technology processed using GEE in Lake Rawa Pening. The satellite image used is Sentinel level-2A with high spatial resolution with a recording time of May 2019 - 2023. This study uses the NDVI method to measure the greenness of vegetation and help identify the density of water hyacinth vegetation. The results of the vegetation density index show that there are five classification for vegetation density levels, and the outcomes of the accuracy test that was conducted range from -0.15 to 0.94. obtained an overall accuracy of 86.6% and a kappa coefficient value of 0.81. These results show that the use of Sentinel 2A imagery can be used for vegetation density index mapping using the NDVI algorithm in GEE with a good level of accuracy and conformity between map and field and the image processing that has been done is appropriate.

Ovarian traits, spawning pattern and season, length at first maturity, and batch fecundity of Caragobius urolepis (Bleeker, 1852) caught from the Vietnamese Mekong Delta

Caragobius urolepis has a wide range of distribution, from brackish to freshwater water, ranging from India to the Philippines and Fiji, including the Vietnamese Mekong Delta (VMD), where it lives mainly in the coastal regions and plays a vital role in food supply. Our preliminary observation showed that its population tended to decline, but little is known about this species. This study, therefore, was conducted to provide data on the ovarian structure, spawning pattern and season, length at first maturity, and batch fecundity of this fish. The study of 306 specimens caught with trawl nets from April 2022 to March 2023 in two coastal areas of VMD—Dong Hai, Bac Lieu (DHBL), and Dam Doi, Ca Mau (DDCM)—showed that this goby spawned more than once because the oocytes in stage IV ovary showed different stages of development. It could release eggs monthly during a 12-month study, with a peak in July–September since stage IV ovaries were found monthly during the study period and the GSI exhibited a high value in July–September. The fish length at first maturity and batch fecundity varied with the site, as they were 18.8 cm and 3,757–9,187 (6,142 ± 707 SE eggs/female) in DDCM and 20.5 cm and 3,760–11,118 (5,634 ± 750 SE eggs/female) in DHBL. The findings provide valuable foundations for exploiting their resources and serve as a basis for studying artificial reproduction. It is suggested to avoid catching these fish species during the breeding season to ensure sustainable exploitation in the future.

Isolation of Trichoderma strains from rhizospheric soil and assessment of their potential for biofertilizer from freshwater aquaculture pond sediment

Abstract. Thi QVC, Nhan TH, Hung NVK, Thuy NP. 2024. Isolation of Trichoderma strains from rhizospheric soil and assessment of their potential for biofertilizer from freshwater aquaculture pond sediment. Biodiversitas 25: 2866-2876. Trichoderma spp. are filamentous fungi found in almost all soils and can synthesize massive quantities of cellulase enzymes which can simply break down cellulose polysaccharides. Freshwater water aquaculture pond sediment has caused some environmental pollution which is required to be properly dealt with. The objective of this study was to isolate Trichoderma strains from rhizosphere soil and to evaluate their potential for biofertilizer from freshwater aquaculture pond sediments. Twenty-six strains of Trichoderma spp. were isolated from soil. The Carboxymethyl Cellulose (CMC) degrading ability of the S25 strain was extremely strong, with a halo diameter zone measuring 8.9±3.8 cm. According to the BLAST result, there was 99.11% similarity between S25 strains and Trichoderma asperelloides, with a max score of 1011 and an E-value of 0.0. The T. asperelloides S25 was selected for bioproduct production. The use of T. asperelloides S25 bioproduct passively enhanced the efficient decomposition of organic fertilizers. After just 30 days of incubation, total organic matter content was ? 30% and material had a spongy, soft, and brown-black in color. According to the Government of Vietnam’s Decree No. 14/2019/ND-CP on fertilizer management, dated September 14, 2019, all treatments were chosen for the production of granular bio-compost. These findings highlight the potential of bioproduct T. asperelloides S25 for sustainable aquaculture practices and organic waste management.

Surface displayed MerR increases mercury accumulation by green microalga Chlamydomonas reinhardtii

Mercury is a highly toxic trace metal that can accumulate in aquatic ecosystems and when resent at high concentrations can pose risks to both aquatic life and humans consuming contaminated fish. This research explores the use of the metalloregulatory protein MerR, known for its high affinity and selectivity toward mercury, in a novel application. Through a cell surface engineering approach, MerR was displayed on cells of green alga Chlamydomonas reinhardtii. A hydroxyproline-rich GP1 protein was used as an anchor to construct the engineered strains GP1-MerR that expresses the fluorescent protein mVenus. The surface engineered GP1-MerR strain led up to five folds higher Hg2+ accumulation compared to the WT strain at concentration range from 10-9 to 10-7 M Hg2+. The binding of Hg2+ via MerR was specific and did not get significantly affected by major freshwater water quality variables such as Ca2+ and dissolved organic matter. The presence of other trace metals (Zn2+, Cu2+, Ni2+, Pb2+, Cd2+) in a same concentration range even resulted in 30–40 % increase in the accumulated Hg. Further, the engineered cells also demonstrated the ability to accumulate Hg2+ from the water extracts of the Hg-contaminated sediment samples. These results demonstrate a novel approach utilizing the cell surface display system in C. reinhardtii for its potential application in bioremediation.

Freshwater water quality criteria for phthalate esters and recommendations for the revision of the water quality standards

With increasing urbanization and rapid industrialization, more and more environmental problems have arisen. Phthalates (PAEs) are the foremost and most widespread plasticizers and are readily emitted from these manufactured products into the environment. PAEs act as endocrine-disrupting chemicals (EDCs) and can have serious impacts on aquatic organisms as well as human health. In this study, the water quality criteria (WQC) of five PAEs (dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP) and di(2-ethylhexyl) phthalate (DEHP)) for freshwater aquatic organisms were developed using a species sensitivity distribution (SSD) and a toxicity percentage ranking (TPR) approach. The results showed that long-term water quality criteria (LWQC) of PAEs using the SSD method could be 13.7, 11.1, 2.8, 7.8, and 0.53 μg/L, respectively. Criteria continuous concentrations (CCC) of PAEs were derived using the TPR method and determined to be 28.4, 13.1, 1.3, 2.5, and 1.6 μg/L, respectively. The five PAEs are commonly measured in China surface waters at concentrations between ng/L and μg/L. DBP, DEHP, and di-n-octyl phthalate (DnOP) were the most frequently detected PAEs, with occurrence rates ranging from 67% to 100%. The ecological risk assessment results of PAEs showed a decreasing order of risk at the national level, DEHP, DBP, DMP, DEP, DnOP. The results of this study will be of great benefit to China and other countries in revising water quality standards for the conservation of aquatic species.

Evaluation of Freshwater Water Quality with Indexes and GIS-Based: A Case Study, Güren Stream (Küre Mountains National Park, Western Black Sea Basin, Turkey)

Evaluation of Freshwater Water Quality with Indexes and GIS-Based: A Case Study, Güren Stream (Küre Mountains National Park, Western Black Sea Basin, Turkey)

Acute toxicity of petroleum asphalt seal coat leachates to Ceriodaphnia dubia is linked to polymer preservatives

Low-VOC waterborne asphalt-emulsion (AE) seal coat is considered more sustainable than solvent-based coal-tar emulsion seal coat because asphalt emulsions contain negligible amounts of carcinogenic PAHs and release fewer harmful volatile organic compounds. Yet, many low-VOC coatings leach water-soluble substances under outdoor conditions. To investigate the chemical composition of seal coat leachates, three AE formulations were cured under natural weathering conditions and exposed to simulated runoff over a 10-day field trial. Runoff was collected and concentrated using ion-exchange solid-phase extraction (SPE) and analyzed using gas chromatography/mass spectrometry (GC–MS). Leached compounds included hydrocarbons, esters, amines, siloxanes, plasticizers, biocides, polyethylene glycol (PEG) ethers, urethanes, and toluene diisocyanate (TDI). Glycol ethers comprised 29–97 % of the measured leachate mass. Two seal coat formulations contained isothiazolinone biocides, methylchloro- and methylisothiazolinone (CMIT/MIT; 0.5 mg/L in runoff), while a third seal coat formulation continuously leached TDI, a reactive polyurethane (PU) precursor (0.7 mg/L in runoff). Biocide-containing leachates showed acute toxicity to the freshwater water flea, Ceriodaphnia dubia after 48 h, while TDI-containing leachate showed no acute toxicity, suggesting that leachate toxicity was due to in-can polymer preservatives. As biocides are implicated in impaired reproductive signaling, these results support the use of alkaline pH to avoid biofouling and reinforce the goal of reducing and/or avoiding the use of biocides altogether, especially for environmentally friendly products.

A mica filter enables bacterial enrichment from large volumes of natural water for sensitive monitoring of pathogens by nanopore sequencing

Nanopore sequencing is extremely promising for the high-throughput detection of pathogenic bacteria in natural water; these bacteria may be transmitted to humans and cause waterborne infectious diseases. However, the concentration of pathogenic bacteria in natural water is too low to be detected directly by nanopore sequencing. Herein, we developed a mica filter to enrich over 85% of bacteria from > 10 L of natural water in 100 min, which led to a 102-fold improvement in the assay limits of the MinION sequencer for assessing pathogenic bacteria. Correspondingly, the sequencing time of S. Typhi detection at a concentration as low as 105 CFU/L was reduced from traditional 48 h to 3 h. The bacterial adsorption followed pseudo-first-order kinetics and the successful adsorption of bacteria to the mica filter was confirmed by scanning electron microscopy and Fourier infrared spectroscopy et al. The mica filter remained applicable to a range of water samples whose quality parameters were within the EPA standard limits for freshwater water. The mica filter is thus an effective tool for the sensitive and rapid monitoring of pathogenic bacteria by nanopore sequencing, which can provide timely alerts for waterborne transmission events.

Influence of salt and temperature in the growth of pathogenic free-living amoebae.

Free-living amoebae are an extensive group of protistans that can be found in a wide variety of environments. Among them, the Acanthamoeba genus and Naegleria fowleri stand out as two of the most pathogenic amoebae and with a higher number of reported cases. N. fowleri is mainly found in warm freshwater water bodies whereas amoebae of the Acanthamoeba genus are broadly distributed through natural and anthropogenic environments. In this regard, the management and the control of the amoebic populations in swimming pools has become a major public health challenge for institutions. The aim of this work was to evaluate the growth pattern of trophozoites of A. griffini and N. fowleri at different temperatures and salt concentrations. Our results showed that A. griffini resisted a higher concentration of salt than N. fowleri. Moreover, no trophozoites could withstand the salt levels of the sea in in vitro conditions. This work supports the contention that salinity could represent an important and useful tool for the control of the most pathogenic amoebic populations in recreational water bodies.

How Daphnia magna Defends Itself against Predators: Mechanisms and Adaptations in a Freshwater Microcosm

The freshwater water flea (Daphnia magna Straus, 1820) is prey for numerous predators. Yet it possesses a wide range of strategies to defend itself against predation. The aim of this work is to investigate the defensive mechanisms employed by D. magna to reduce predation by the coelenterate Hydra viridissima, and two planarians, Polycelis felina and Dugesia gonocephala. To do this, we used a freshwater microcosm. An additional aim is to investigate interactions with the presence of the isolated endosymbiotic algae from green hydra, thus combining and observing the interaction of the zooplankton and microalgal component. Each experiment included five replicates (13.5 °C, 25 °C), in crystallizing glass containers (60 mL volume, 60 mm diameter, 35 mm height), including satiated (fed with larvae of Artemia salina) and starved predators, respectively (one or five individuals of a particular predator species in one microcosm). As the isolated microalgae are unique, we tracked the following three mechanisms of Daphnia defense for the first time including precisely this microalgal component: (i) grouping (visual magnification), i.e., two or more Daphnia holding together; (ii) the phenomenon of overproduction, i.e., any number of Daphnia in one container above the 10 initially added individuals; and (iii) accelerated movement (“bullet movement”), i.e., high-speed movements in particular microcosms. The results provide new information for a better understanding of the interspecific relationships in systems that include both zooplankton and microalgal components.

Persistent Organic Pollutants and Suspended Particulate Matter in Snow of Eastern Siberia in 2009-2023: Temporal Trends and Effects of Meteorological Factors and Recultivation Activities at Former Industrial Area.

Suspended particulate matter (SPM), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCP) were studied in the snow cover at urban and suburban localities in the Irkutsk region, Eastern Siberia for their temporal variations in 2009-2023, daily deposition fluxes (DDFs), and effects of some meteorological factors, as well as the effects of different technogenic activities in the industrial area of the former organochlorine enterprises of Usol'ekhimprom. SPM loads at both stations were found to be at a low level of pollution. The levels of HCB, α + γ-HCH, and ∑p,p'-DDX were lower than Russian maximum permissible levels (MPLs) in drinking water, groundwater, and surface water for household drinking and cultural purposes. The sums of all organochlorine compounds studied in snow were higher than the MPL in freshwater water bodies for fishery purposes. The levels of the DDFs of HCHs, DDTs, and heptachlorinated PCB decreased, di- and trichlorinated PCB levels increased, and HCB levels changed at a polynomial line during 2009-2023. The change in the relative composition of PCBs was found as a result of recultivation activities at the industrial area of the former organochlorine enterprise of Usol'ekhimprom. The air humidity and temperature are the key meteorological factors affecting the DDFs of PCBs and OCPs.

Combined effects of nanoplastics and elevated temperature in the freshwater water flea Daphnia magna

Global warming and nanoplastics (NPs) are critical global issues. Among NPs, one of the most hazardous types of plastics, polystyrene (PS), poses ecotoxicological threats to several freshwater organisms. The degree of toxicity of PS-NPs is strongly influenced by various environmental factors. This study illustrates the combined effects of temperature and PS-NPs on the water flea Daphnia magna. The sensitivity of D. magna to PS-NPs was tested under control (23 °C) and elevated temperatures (28 °C). As a result, increased temperatures influenced the uptake and accumulation of PS-NPs. Co-exposure to both higher temperatures and PS-NPs resulted in a drastic decrease in reproductive performance. The level of oxidative stress was found to have increased in a temperature-dependent manner. Oxidative stress was stimulated by both stressors, leading to increased levels of reactive oxygen species and antioxidant enzyme activity supported by upregulation of antioxidant enzyme-related genes under combined PS-NPs exposure and elevated temperature. In the imbalanced status of intracellular redox, activation of the p38 mitogen-activated protein kinase signaling pathway was induced by exposure to PS-NPs at high temperatures, which supported the decline of the reproductive capacity of D. magna. Therefore, our results suggest that PS-NPs exposure along with an increase in temperature significantly affects physiological processes triggered by damage from oxidative stress, leading to severely inhibited reproduction of D. magna.

Energy, exergy, economic, exergoeconomic, exergoenvironment, and enviroeconomic (6E) analysis of solar stills—A critical review

AbstractDrinking water is a crucial need for human survival and solar stills (SSs) have emerged as a cost‐effective solution to meet this need from an economic point of view. In this work, the working of various SSs, their productivity factors, and various devices that can be integrated to improve their efficiency have been studied. The conversion of saline water into freshwater water using SSs has the potential to address the issue of drinking water. This study highlights the importance of SSs as a viable and sustainable solution for drinking water access. On the basis of various parameters correlating to the performance of the SSs, energy, exergy, economics, exergoeconomics, exergoenvironment, and enviroeconomics analysis has been analyzed in this study. To improve the performance and sustainability of SSs, various combinations were studied. These combinations include SSs with different nanoparticle coatings, phase‐change materials, photovoltaic modules, external condensers, wick materials, and reflectors. It is concluded that a comprehensive framework that integrates thermodynamic, economic, and environmental criteria can guide the development of more efficient and sustainable SS technologies.

Assessing Freshwater Microbiomes from Different Storage Sources in the Caribbean Using DNA Metabarcoding.

Next-generation sequencing (NGS) and the technique of DNA metabarcoding have provided more efficient and comprehensive options for testing water quality compared to traditional methods. Recent studies have shown the efficacy of DNA metabarcoding in characterizing the bacterial microbiomes of varied sources of drinking water, including rivers, reservoirs, wells, tanks, and lakes. We asked whether DNA metabarcoding could be used to characterize the microbiome of different private sources of stored freshwater on the Caribbean Island nation of Antigua and Barbuda. Two replicate water samples were obtained from three different private residential sources in Antigua: a well, an above-ground tank, and a cistern. The bacterial microbiomes of different freshwater sources were assessed using 16S rRNA metabarcoding. We measured both alpha diversity (species diversity within a sample) and beta diversity (species diversity across samples) and conducted a taxonomic analysis. We also looked for the presence of potentially pathogenic species. Major differences were found in the microbiome composition and relative abundances depending on the water source. A lower alpha diversity was observed in the cistern sample compared to the others, and distinct differences in the microbiome composition and relative abundance were noted between the samples. Notably, pathogenic species, or genera known to harbor such species, were detected in all the samples. We conclude that DNA metabarcoding can provide an effective and comprehensive assessment of drinking water quality and has the potential to identify pathogenic species overlooked using traditional methods. This method also shows promise for tracing the source of disease outbreaks due to waterborne microorganisms. This is the first study from small island countries in the Caribbean where metabarcoding has been applied for assessing freshwater water quality.

Effect of co-digestion with water hyacinth, inoculum concentration and dilution on biogas production of fish waste

A report from the FAO (Food and Agriculture Organization) estimates that 9.1 million tons of Fish wastes (FW) are thrown away each year. Water hyacinth (WH) is the most invasive water weed that thrives in freshwater water and has impacts on the environment, ecology, and society. The waste generated is either discarded onto the open ground or disposed into pits which result in environmental pollution and health hazards. FW and WH can be used for biogas production. However, FW digests quickly and produces a lot of ammonia and Volatile fatty acids (VFAs) which inhibit the digestion when digested alone, it has also a low carbon to nitrogen (C/N) ratio; consequently, it is not directly suitable for anaerobic digestion (AD). In this regard, co-digestion with WH (high C/N ratio) prior to AD is necessary. To examine the effects of the operating factors: Substrate ratio (WH: FW), Inoculum concentration (IC) and Dilution, Central composite design (CCD) in Design Expert 13 software was used to design experiments of three factors at five levels which resulted in 17 runs. Laboratory scale experiments were carried out under mesophilic temperature (37 ℃). The maximum biogas with the highest methane content of 68.15% was produced at the substrate ratio of 25:75 g/ 250 mL (WH: FW), 15 g/ 250 mL of IC and dilution of 95 mL. The biogas yield increased by 16.1% and 32.4% compared to pure WH and FW respectively. This implied that the operating conditions were efficient in maximising the biogas yield. FW had a lower C/N ratio; further study needs to consider co-digestion with other higher C/N ratio substrates.

Spatio-temporal dynamics of phytoplankton in a diversion reservoir and the major influencing factors: taxonomic versus functional groups classification.

Identifying factors affecting phytoplankton dynamics is crucial to the management of aquatic ecosystems. A lot of scholars have conducted intensive studies on phytoplankton in lake or reservoirs, but not many studies have been conducted on diversion reservoirs. To explore the seasonal and spatial variation of phytoplankton communities and their relationship with environmental factors in the context of water diversion, a case study was carried out at XiKeng (XK) reservoir in South China. In this study, month-by-month water samples and phytoplankton were collected from this reservoir from December, 2021, to July, 2022. The results showed that the phytoplankton community was characterized by significant spatial and temporal variations. There were significant differences in phytoplankton abundance and structure in the reservoirs in terms of time. The abundance of phytoplankton cells and the proportion of Cyanobacteria in the reservoir showed a trend of increasing from autumn to spring and then decreasing from spring to summer, while the functional group evolved from S1 in autumn to SN in spring and summer. The abundance of phytoplankton was influenced by the dynamic water division and the characteristics of the reservoir itself, resulting in a spatial distribution characteristic of AIII > AII > AI. Water temperature (WT) and nutrients were the key factors driving the changes in phytoplankton abundance and community structure in the reservoir. These findings will deepen our understanding of the spatial and temporal dynamics of phytoplankton community structure in diversion reservoirs and provide a basis for freshwater water ecological management strategies.

Chemical Oxygen Demand as a Measure of Fluvial Organic Matter Oxidation State

AbstractThe oxidative ratio (OR) of the terrestrial biosphere is directly related to the size of the terrestrial biosphere carbon sink. In turn, OR of naturally occurring organic matter can be directly related to the oxidation state of the carbon in naturally occurring organic matter (Cox). Chemical oxygen demand (COD) is a widely measured water quality parameter that has been used as a short‐term substitute for the biochemical oxygen demand (BOD). Here, we propose that if the concentration of reduced species is known, then COD measurement can be used to assess the oxidation state (Cox) of fluvial organic C. Using a Bayesian hierarchical modeling approach, this study analyzed 21 years of water quality monitoring across England to calculate Cox of fluvial organic matter. The study showed that (a) COD could not be considered separately from the reduced species (e.g., NH4) commonly occurring in freshwater water samples, but it was still possible to calculate the Cox of dissolved organic carbon (DOC) and particulate organic carbon (POC). (b) The median Cox of DOC was 0.23 with a 95th percentile range of −0.1 to 0.4. (c) The median Cox of POC was 0.20 with a 95th percentile range of 0.03–0.37. (d) The estimated Cox in fluvial systems confirms that BOD is decoupled from the production of CO2. Including new Cox estimates in the global estimate of OR gives a new median value of 1.059 with a 95th percentile range of 1.047–1.071, giving the annual flux of CO2 to land (fland) of 1.45 ± 0.1 Gt C/year.

Climate Change May Impact Nile Tilapia, Oreochromis niloticus (Linnaeus, 1758) Distribution in the Southeastern Arabian Peninsula through Range Contraction under Various Climate Scenarios

Climate change is expected to affect freshwater water bodies worldwide, especially those located in semiarid and arid regions, including the Arabian Peninsula. Species distribution modeling has been widely used to predict the effects of climate changes on aquatic species. Occurrence records of the cichlid fish Nile tilapia, Oreochromis niloticus, were geographically mapped, followed by the implementation of species distribution models to delineate its range within the sensitive inland water system of the southeastern Arabian Peninsula. The analysis encompassed the examination of species presence data in the context of environmental variables, leading to the development of an ensemble model for habitat suitability, combining four distinct species distribution models. The findings indicated that the mean diurnal range and precipitation seasonality emerged as the most influential factors in predicting the suitability of habitats for O. niloticus. The response curve analysis indicated that the presence probability of O. niloticus decreased with increasing mean diurnal range and decreasing precipitation seasonality. The suitable distribution ranges for O. niloticus in the studied area were mainly distributed in the northeast of this region, where native/endemic fish diversity is high. The ensemble model results specified a significant impact of climate change on O. niloticus distribution, so highly suitable areas for this species will be reduced, while areas with low to moderate suitability increase slightly or remain unchanged. While O. niloticus is anticipated to display resilience and prosper under the influence of climate change, it remains paradoxical that its habitats are at risk of being compromised by climate-induced alterations. Consequently, even this resilient species stands susceptible to the repercussions of climate change. Due to the worldwide severe impacts of Nile tilapia, regular monitoring of freshwater ecosystems and fish fauna—especially in the northeast of the Arabian Peninsula, which has currently been invaded by this alien species—and protecting the region from key anthropogenic stressors are recommended to successfully conserve the freshwater fishes, which include about 22 recognized fish species in 16 genera, 10 families, 7 orders, and a class including 20 natives (7 endemic) species, out of which 13 species co-occur in sympatricity with O. niloticus.

Synergistic toxic mechanisms of microplastics and triclosan via multixenobiotic resistance (MXR) inhibition–mediated autophagy in the freshwater water flea Daphnia magna

Since a mixed state of environmental contaminants, including microplastics (MPs), heavy metals, pharmaceuticals, and personal care products (PPCPs), exists in aquatic ecosystems, it is necessary to evaluate not only the adverse effects of exposure to a single stressor but to combined stressors. In this study, we exposed the freshwater water flea Daphnia magna to 2 μm MPs and triclosan (TCS), one of PPCPs, for 48 h to investigate the synergistic toxic consequences of simultaneous exposure to both pollutants. We measured in vivo endpoints, antioxidant responses, multixenobiotic resistance (MXR) activity, and autophagy-related protein expression via the PI3K/Akt/mTOR and MAPK signaling pathways. While MPs single exposure did not show toxic effects in water fleas, simultaneous exposure to TCS and MPs was associated with significantly greater deleterious effects in the form of increased mortality and alterations in antioxidant enzymatic activities compared with water fleas exposed to TCS alone. In addition, MXR inhibition was confirmed by measurement of the expression of P-glycoproteins and multidrug-resistance proteins in MPs-exposed groups, which led to the accumulation of TCS. Overall, these results suggest that simultaneous exposure to MPs and TCS resulted in higher TCS accumulation via MXR inhibition, leading to synergistic toxic effects such as autophagy in D. magna.