Pollution In Freshwater Ecosystems Research Articles

Pollution of Freshwater Ecosystems by Microplastics: A Short Review on Degradation, Distribution, and Interaction with Aquatic Biota

Pollution of Freshwater Ecosystems by Microplastics: A Short Review on Degradation, Distribution, and Interaction with Aquatic Biota

Evaluation of Microplastics and Microcystin-LR Effect for Asian Clams (Corbicula fluminea) by a Metabolomics Approach.

Microplastics (MP) and microcystins (MCs) are two co-occurring pollutants in freshwater ecosystems that pose significant risks to aquatic organisms and human health. This study investigates the interactions between MP and MCs and their effects on the metabolic responses of freshwater aquaculture. Asian clams have been used as an indicator of microplastic pollution in freshwater ecosystems. The present study investigates metabolic responses of Asian clams during microplastic and microcystin-LR stress to identify health impacts and elucidate mechanistic effects of external stressors on Asian clams. A liquid chromatography/mass spectrometry (LC-MS)-based metabolomics approach was used to identify metabolic perturbations and histological section technique was used to assess changes of tissues from different Asian clam treatment groups. The results showed significantly pathological changes in the gills and hepatopancreas in experimental clam compared to control (healthy) clam. Metabolomics revealed alterations of many metabolites in the hepatopancreas of six Asian clam comparison groups, reflecting perturbations in several molecular pathways, including energy metabolism, amino acid metabolism, protein degradation/tissue damage, and oxidative stress. Overall, this study emphasizes the importance of understanding the interactions between MP and MCs and the need for proactive measures to safeguard freshwater ecosystems and human health.

Modeling the effect of fish migration on the horizontal distribution of microplastics in freshwater and ecological risks in the food web: Influence of habitat

Microplastics (MPs < 5 mm) pollution is a widespread phenomenon in freshwater ecosystems. While the role of physiochemical factors in the migration and distribution of MPs is understood, the impact of biological migration remains less clear. The influence of nekton migration determined by habitat suitability on the distribution of MPs and the consequent ecological risks to the regional food web is investigated in the freshwater environment by using Baiyangdian Lake (China) as a case study. The key findings reveal that fish migration significantly alters the horizontal distribution of MPs in the water environment, with a higher degree of fish aggregation in high suitability habitats leading to an increased presence of MPs due to their ingestion and excretion behaviors. In both high and low suitability habitats, MPs are found to bioconcentrate in fish, suggesting a significant risk to aquatic ecosystems. Despite the lack of evidence supporting MPs biomagnification, the results indicate that MPs are more likely to be biomagnified within the food web of high suitability habitats due to the enhanced foraging capabilities of aquatic organisms. These findings highlight the critical need to consider biological factors, such as nekton migration, in understanding and addressing MPs pollution in freshwater ecosystems.

Assessment of road run-off and domestic wastewater contribution to microplastic pollution in a densely populated area (Flanders, Belgium)

Plastics are omnipresent in our daily life. Unfortunately, the produced plastics will partly end up in the environment including aquatic ecosystems. People often refer to littering or illegal waste dumping as sources of plastic emission to the environment. However, daily-life sources could also, unknowingly, contribute considerably to the total microplastic pollution in the ecosystem. Hence, there is an urgent need to study these potential sources. In this research, two common sources, i.e. domestic wastewater and road run-off from tire and road wear particles, were studied in detail to quantify the relative contribution of both domestic sources towards microplastic pollution in freshwater ecosystems in Flanders, Belgium.This assessment shows that every person (in studied area) emits on average 1145 microplastics (25–1000 μm) daily through domestic wastewater, resulting in a yearly discharge of 418,000 microplastic particles per person. The road run-off samples contained between 0.02 and 9.2 mg tire wear particles per litre per day, which corresponds to an emission of 10.8 mg tire wear particles per driven vehicle km.The gross and net emissions of both above mentioned microplastic sources were extrapolated to the whole Flanders region using an emission model. From the yearly gross microplastic pollution in the domestic wastewater, 623 kg (20%) will be discharged in the freshwater. The highest losses originated from the households that have a private drain or are not (yet) connected to an active wastewater treatment plant. In Flanders, the yearly net microplastic emission into the aquatic environment of tire wear particles is estimated to be 246 tonnes (38%), mainly from the direct run-off from the road surface. Based on the results, specific mitigation measures can be installed to reduce the emission of microplastics towards the freshwater ecosystem. Other sources should be quantified in a similar way for a more holistic strategy to counteract plastic pollution.

Impact of Microplastic Pollution on Freshwater Ecosystems and Effective Mitigation Measures in Canada

Purpose: This study investigates the impact of microplastic pollution on freshwater ecosystems and effective mitigation measures in Canada.&#x0D; Methodology: The study adopted a desktop methodology. Desk research refers to secondary data or that which can be collected without fieldwork. Desk research is basically involved in collecting data from existing resources hence it is often considered a low-cost technique as compared to field research, as the main cost is involved in executive’s time, telephone charges and directories. Thus, the study relied on already published studies, reports and statistics. This secondary data was easily accessed through the online journals and library.&#x0D; Findings: The literature review and research findings demonstrate that microplastic pollution is significantly impacting freshwater ecosystems in Canada. Microplastics can accumulate in water, biota, and sediments, leading to water quality changes, ecological disruptions, and potential risks to human health. The study also highlights the ecological and societal impacts of microplastic pollution, such as changes in habitat structure, alterations in food webs, and potential health risks. Various mitigation measures, including source reduction, wastewater treatment, education and awareness, policy and regulatory measures, and ecosystem-based approaches, are effective in reducing microplastic pollution in freshwater environments.&#x0D; Recommendations: This study contributes to the understanding of microplastic pollution's impact on freshwater ecosystems and effective mitigation measures in Canada. The research advances knowledge in environmental science, freshwater ecology, and pollution management, providing insights into sources, pathways, and impacts of microplastic pollution in freshwater ecosystems, and the effectiveness of various mitigation measures. The findings have practical implications for policymakers, environmental managers, and stakeholders involved in freshwater management and pollution control, highlighting the need for interdisciplinary approaches, stakeholder engagement, and evidence-based policy and management strategies to mitigate the negative effects of microplastic pollution on freshwater ecosystems and safeguard their health and sustainability.&#x0D;

The invasive red swamp crayfish (Procambarus clarkii) as a bioindicator of microplastic pollution: Insights from Lake Candia (northwestern Italy)

Microplastic pollution has become pervasive. Identifying a bioindicator species to track the occurrence and effects of microplastics (MPs) on ecosystems is crucial for determining their impact on the environment. The digestive tract of Procambarus clarkii was thought to be of interest for investigating MPs accumulation in freshwater organisms. Our hypothesis was that the same type of MPs found in abiotic compartments (water and sediment) could be found in P. clarkii, which would make it an ideal candidate for use as a bioindicator of MP pollution in freshwater ecosystems. Water, sediment, and P. clarkii specimens were collected from four sites in a lentic ecosystem (Lake Candia; northwestern Italy) for two consecutive years (2021–2022). The mean MPs abundance was 1.75 ± 0.95 items/m3 in 2021 and 2 ± 0.81 items/m3 in 2022 in the water samples and 6.75 ± 1.5 items/kg and 8 ± 0.81 items/kg in the sediment samples in 2021 and 2022, respectively. In 2021, the average was 0.06 ± 0.07 items/g in the males and 0.05 ± 0.05 items/g in the females; in 2022, the average was 0.04 ± 0.05 items/g and 0.05 ± 0.06 items/g in the males and the females, respectively. MP fibers and fragments (black, white, blue, light blue) of polypropylene and polyethylene terephthalate were found in the biotic and the abiotic compartments. The generalized linear mixed model revealed that the number of items/g was predicted only by total weight: the lowest number of items/g was recorded for crayfish with the highest weight probably due to the feeding habits of P. clarkii. Our findings suggest that the invasive P. clarkii (smaller individuals, in particular) could be a good candidate bioindicator for MP pollution since the same type of MP items were recorded in the abiotic compartments. Further research is needed to better understand the feeding behavior of P. clarkii and the dynamics of MPs in aquatic ecosystems.

Analysis of Differential Gene Expression of the Aquatic Insect Protohermes costalis (Walker) (Megaloptera: Corydalidae) in Response to Cadmium Exposure.

Heavy metal pollution in freshwater ecosystems is a serious threat to aquatic organisms. Species of Megaloptera are important predators of aquatic invertebrates and have been widely used as bioindicators in assessing the quality of freshwater ecosystems. In this study, we determined the differential gene expression profile of Protohermes costalis (Walker) (Megaloptera: Corydalidae) in response to cadmium (Cd) exposure by using transcriptome analysis. A total of 60,627 unigenes were obtained in the transcriptomes of 150 mg/liter (PL), 1,000 mg/liter (PH) CdCl2 treatment, and the no Cd control (PC). Differential expression gene (DEG) analysis by pairwise comparison identified 2,794 DEGs after filtering the noninsect genes and repetitive counts. 606 DEGs were shared in comparisons of PL versus PC and PH versus PC, with 165 DEGs consistently up-regulated and 441 down-regulated by both PL and PH. Six heat shock proteins (HSPs) in the HSP70 family were identified in P. costalis and PcosHSP68 was up-regulated by both PL and PH. Real-time quantitative polymerase chain reaction (RT-qPCR) confirmed that the expression levels of PcosHSP68 in PL and PH were higher than that of PC by 31 and 197%, respectively. These results showed that exposure to Cd altered the gene expression profiles of P. costalis and the transcriptome data presented in this study provide insight into future studying on molecular mechanisms of Cd toxicity to these insects.

Evaluation of Nuphar lutea as bioindicator of metal pollution in freshwater ecosystems

Macrophytes have a capacity to absorb elements from the water and sediment and some species can be bioindicators of pollution. The uptake of 12 metals by Nuphar lutea from 56 water bodies was studied to evaluate its bioaccumulation potential and bioindication suitability. Study sites were grouped in three types: urban, agricultural and semi-natural (forests) according to land cover and anthropogenic activities in their surroundings. Concentrations of Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb and Zn were determined by atomic absorption spectrometry. Results highlighted higher levels of pollution (e.g. Cd, Cr, Fe, Ni and Zn concentrations in sediments) in urban and agricultural areas than in forest areas. The levels of metals in leaves were high and contents differed between sites exposed to various metal sources. The lowest concentrations of Co, Mn, Ni, Pb, Zn in plants were noted in forest areas; the highest Cd content in agricultural sites while the highest Cr, Fe, K content in urban sites. Neural networks demonstrated similarities in sediments and leaves of N. lutea in response to multi-elemental pollution. Results indicated on the possibility of using the leaves of N. lutea as an indicator of pollution in water bodies (in biomonitoring process). Eggs of Little Bitterns show high variation and their size increases with latitude.

Natural Antioxidants can Improve Microplastics-Induced Male Reproductive Impairment in the African Catfish (Clarias Gariepinus)

This study was conducted to explore the protective potential of three different antioxidant supplements, lycopene, citric acid, andChlorella, against reproductive injuries induced by microplastics (MPs) in freshwater mature male catfish. A total of 150 mature male African catfish (Clarias gariepinus) were assigned to five treatment groups as follows: control group fish were fed with control diet, the second group fish were fed with 500 mg/kg MP diet, and the remaining three groups of fish were fed with 500 mg/kg MP diet plus lycopene (500 mg/kg diet), citric acid (30 g/kg diet), andChlorella(50 g/kg diet), respectively, for 15 days. Ingestion of MPs significantly decreased serum luteinizing hormone, follicle-stimulating hormone, sex steroid (testosterone and estradiol) levels and sperm count, spermatocrit, motility, and viability. It also induced histological alterations and degenerative changes in testicular tissues. Administration of lycopene andChlorellawith MP diets maintained hormone levels comparable to those in the control group, enhanced sperm quality, and decreased testicular histological damage.Chlorellawas more effective in enhancing sperm quality, and lycopene was more efficient in alleviating testicular tissue damage. Citric acid supplementation was irrelevant in mitigating MP-induced injury. This study indicated that both lycopene andChlorellaameliorated the MP-induced reproductive dysfunction by improving reproductive hormonal levels, sperm parameters, and histological configuration, whereas the citric acid dose used in this study was not effective in ameliorating the MP-induced reproductive stress. Additional research and monitoring of MP-induced pollution in freshwater ecosystems are required to avoid the severity of reproductive toxicity in freshwater fish.

Goals and approaches in the use of citizen science for exploring plastic pollution in freshwater ecosystems: A review

The role of citizen science in environmental monitoring has received interest in the research community over the last decade, with citizen scientists playing a key role in engaging with and gathering scientific evidence to support natural resource management. Likewise, the involvement of citizen science in aquatic research is growing. One area of aquatic research where there has been successful application of citizen science is in support of plastic-pollution research. Plastic-pollution research benefits from support by citizen scientists both because of the ubiquity of plastic within our environments, requiring data to be collected from a wide geographical area, and because of the need for systemic behavior change at both individual and societal levels. Recent studies highlight citizen science contributions to plastic-pollution research within marine systems, but our knowledge is limited about how citizen science can support limnetic plastic-pollution research, with no known published systematic reviews. The involvement of citizen science within freshwater monitoring has been widely discussed, but most peer-reviewed literature focuses on commonly targeted water-quality parameters (e.g., nutrients). This is not surprising given that freshwater plastic waste is a newly emerging field of interest; thus, the support of citizen science in this research area is only just beginning. This review is the 1st to explore the status of freshwater citizen science focused on plastic pollution. Based on a synthesis of 12 peer-reviewed publications, we considered the environmental and geographic extent of the research, research scope, methods, involvement of citizen science, and data quality. We also discuss how citizen science can contribute to emerging issues in freshwater science. Through our review we found that the use of citizen science within the field of freshwater plastic-pollution research remains rare, with most projects following the contributory model of citizen participation. Additionally, methods and standardized approaches for citizen recruitment, engagement, and training were limited in the peer-reviewed literature. Greater transparency of methods and approaches used will be key to opening up the potential for citizen science within this evolving research field. This review can be used as a starting point for researchers to develop their own freshwater plastic-waste monitoring programs involving citizen scientists.

Effects of Land Use and Pollution Loadings on Ecotoxicological Assays and Bacterial Taxonomical Diversity in Constructed Wetlands

Freshwater ecosystems are affected by anthropogenic alterations. Different studies have extensively studied the concentrations of metals, nutrients, and water quality as measurements of pollution in freshwater ecosystems. However, few studies have been able to link these pollutants to bioindicators as a risk assessment tool. This study aimed to examine the potential of two bioindicators, plant ecotoxicological assays and sediment bacterial taxonomic diversity, in ecological risk assessment for six freshwater constructed wetlands in a rapidly urbanizing watershed with diverse land uses. Sediment samples were collected summer, 2015 and 2017, and late summer and early fall in 2016 to conduct plant ecotoxicological assays based on plant (Lepidium, Sinapis and Sorghum) growth inhibition and identify bacterial taxonomical diversity by the 16S rRNA gene sequences. Concentrations of metals such as lead (Pb) and mercury (Hg) (using XRF), and nutrients such as nitrate and phosphate (using HACH DR 2800TM spectrophotometer) were measured in sediment and water samples respectively. Analyses of response patterns revealed that plant and bacterial bioindicators were highly responsive to variation in the concentrations of these pollutants. Hence, this opens up the scope of using these bioindicators for ecological risk assessment in constructed freshwater wetland ecosystems within urbanizing watersheds.

Use of the Zebra Mussel Dreissena polymorpha (Mollusca, Bivalvia) as a Bioindicator of Microplastics Pollution in Freshwater Ecosystems: A Case Study from Lake Iseo (North Italy)

The monitoring of microplastics pollution in freshwater environments trails behind its practice in marine ecosystems. We evaluated the use of the invasive zebra mussel (Dreissena polymorpha) as a potential bioindicator of microplastic litter in freshwater lakes. Samples were collected from three sites (Lovere, Costa Volpino, Castro) at the northern end of Lake Iseo (one of the major subalpine lakes in north Italy) and compared for water physicochemical parameters, biometrical features of zebra mussels, and microplastics items/specimens (color, shape, size, and chemical composition). We hypothesized that since a wastewater treatment plant (WWTP) on the Oglio River discharges into this area of the lake, the microplastics in D.polymorpha could be measured and compared in samples from the three sites at different distances from the WWTP. There was no difference in the physicochemical water parameters and biometric features between the samples from the three sites, whereas there was a significant difference in items/specimen between the sites in decreasing order (mean ± standard deviation): Costa Volpino (0.23 ± 0.43) &gt; Lovere (0.07 ± 0.25) &gt; Castro (0.03 ± 0.18). The chi-square test showed a significant difference in shape, color, and chemical composition frequency in the samples from the three sites. The chemical composition of the microplastics was polyethylene terephthalate (45%), nylon (20%), polypropylene (20%), polyamide resin (10%), and polyvinyl chloride (5%). Our data show that the amount of microplastics the zebra mussel accumulated was greater the closer the sampling site to the WWTP. Our findings suggest that the zebra mussel may provide a useful tool to monitor microplastics pollution in lakes.

Plastic pollution: A focus on freshwater biodiversity.

Plastics are dominant pollutants in freshwater ecosystems worldwide. Scientific studies that investigated the interaction between plastics and freshwater biodiversity are incipient, especially if compared to the marine realm. In this review, we provide a brief overview of plastic pollution in freshwater ecosystems around the world. We found evidence of plastic ingestion by 206 freshwater species, from invertebrates to mammals, in natural or semi-natural ecosystems. In addition, we reported other consequences of synthetic polymers in freshwater ecosystems-including, for instance, the entanglement of animals of different groups(e.g., birds). The problem of plastic pollution is complex and will need coordinated actions,such as recycling programs, correct disposal, stringent legislation, regular inspection, replacement of synthetic polymers with other materials, and ecological restoration. Current information indicates that the situation in freshwater ecosystems may be as detrimental as the pollution found in the ocean, although highly underappreciated.

Urbanization and hydrological conditions drive the spatial and temporal variability of microplastic pollution in the Garonne River

Microplastic (MP) pollution represents a novel environmental pressure acting on freshwater ecosystems. Improving our understanding of the dynamics of MP pollution in freshwater ecosystems is therefore a prerequisite for managing and limiting this pollution. In this study, we quantified the spatial and temporal variability of MP (size range 700 μm – 5 mm) pollution in surface water in 14 sites located across the Garonne river catchment (Southwestern France, 6 in the main river and 8 tributaries). MP concentration averaged 0.15 particles.m−3 (± 0.46 SD) and strongly varied both in space and in time. We found that the spatial variation in MP concentration was driven by urbanization and that the temporal variation in MP concentration and MP size was driven by hydrological conditions, with higher concentrations and smaller particles sizes in warm seasons with low discharge. Polyethylene (44.5%), polystyrene (30.1%) and polypropylene (18.2%) were the main polymers and their proportion did not vary significantly across sampled sites. Particle color was associated with polymer type, with a high proportion of white particles in polystyrene. We also found a significant and negative relationship between MP size and the distance to the source in sites located in the main stream. MP pollution across watershed, from headwater tributaries to lowland rivers, is dynamic, and further studies are needed to improve the resolution of our knowledge of spatial and temporal patterns of MP pollution in freshwater ecosystems.

Protocol for microplastic pollution monitoring in freshwater ecosystems: Towards a high-throughput sample processing - MICROPLASTREAM

Robust and reproducible quantification of microplastic pollution in freshwater ecosystems requires the processing of a large amount of samples collected in varying environmental conditions. Such samples are characterized by a high amount of organic matter compared to microplastics and are highly variable in terms of the quantity and the composition of matrices, requiring a standardized analytical protocol for sample treatment and analysis. However, two important and time-consuming steps for microplastic recovery are the elimination of organic matter and microscopic inspection of samples. Here, we developed and validated a protocol, targeting particles with length ranging from 700 µm to 5 mm, that includes a double-step digestion of organic matter, consisting of incubation with potassium hydroxide followed by hydrogen peroxide solutions, and two stereomicroscopic analyses. In addition, we developed several technical improvements allowing reducing the time needed to process samples, such as the design of an adapted filter-cap to improve the content transfer. The absence of physical and chemical alterations in the investigated microplastic pellets and the average reduction of 65.8% (± 9.59 SD) of organic matter in real samples demonstrated that our protocol is fit for purpose. We recommend a second stereomicroscopic analysis to avoid underestimating microplastic concentration and particle size distribution biased towards larger particles. When used for a large-scale monitoring of microplastic pollution, this protocol resulted in an estimated time of 38 h for one person for the treatment of a batch of 24 samples, allowing a higher throughput sample processing and reproducible quantification.• Protocol customization towards high-throughput sample processing• Double step digestion to improve organic matter elimination• Importance of stereomicroscopic analysis for microplastic recovery

Toxic effects of naturally-aged microplastics on zebrafish juveniles: A more realistic approach to plastic pollution in freshwater ecosystems

We aim at evaluating the toxicity of naturally-aged polystyrene microplastics (MPs) in Danio rerio at intermediate development stage. Animal models were stactically exposed to 4 × 104 and 4 × 106 microparticles/m3 for five days – this concentration is environmentally relevant. We evaluated MP’s impact on animals’ nutritional status and REDOX balance, as well as its potential neuro- and cytotoxic action on them. Initially, MPs did not induce any change in total carbohydrates, triglycerides and total cholesterol levels. MP accumulation was associated with oxidative stress induction, which was inferred by the nitrite and thiobarbituric acid reactive substances levels. Furthermore, we observed that such stress was not counterbalanced by increase in the assessed enzymatic (total glutathione, catalase and superoxide dismutase) and non-enzymatic (total thiols, reduced glutathione and DPPH radical scavenging activity) antioxidants. The association between high acetylcholinesterase activity and numerical changes in neuroblasts distributed on animals' body surface confirmed MP’s neurotoxic potential. MP’s ability to induce apoptosis and necrosis processes in animals' erythrocytes suggested its cytotoxic action; therefore, the present study is pioneer in providing insight on how MPs can affect young freshwater fish at environmental concentrations. It is essential knowing the magnitude of these pollutants’ impact on the ichthyofauna.

Tatlısu ekosistemlerinde mikroplastik kirliliği: Türkiye'den bir örnek çalışma

Microplastic pollution has increased rapidly over recent decades and accepted as an emerging thread. However, the effects and dimensions of microplastic pollution on aquatic ecosystems have not been fully understood yet. Most of these few studies have been carried out in marine ecosystems and the number of studies on freshwater are very limited. In this study, microplastic (&lt;5 mm) pollution level of surface water samples taken from Cevdet Pond (Yozgat/Turkey) was investigated. Water samples (150 L) were taken from 5 stations and microplastic particles were extracted via density separation method. Random particles were examined both visually and spectrophotometrically (µ-Raman). According to station averages, there were 233 microplastic particles in 1 m3 of the pond water. Highest number of MP particles observed in 100-250 µm (56%) size class. Most abundant microplastic type and colour are fiber (91%) and blue (36%) respectively. Polypropylene (50%) and polyethylene (40%) were the most abundant type of polymers according to µ-Raman analysis. The presence of microplastic pollution in an area where human impact is relatively low, indicates the prevalence of microplastic pollution in freshwater ecosystems.

Investigation of Microplastics in Freshwater Mussels (Lasmigona costata) From the Grand River Watershed in Ontario, Canada

Microplastics have been identified as a widespread, persistent environmental pollutant. The investigation of microplastics in marine ecosystems has been prevalent in the literature; however, much less consideration has been given to this form of pollution in freshwater ecosystems. Relatively few studies have considered the uptake of microplastics in freshwater mussels. This study investigated the presence of microplastics in fluted-shell mussels (Lasmigona costata) collected from various sites in the Grand River watershed, Southern Ontario’s largest watershed and home to one million people. The soft tissue of adult mussels underwent enzyme digestion, followed by filtration to isolate undigested particles. Particles were removed and analyzed using Raman spectroscopy to determine their composition. Ten different polymers were identified in the sampled mussels, with polypropylene-co-polyethylene being the most prevalent. Microplastic particles were detected in 71% of mussels with the greatest number of particles observed in a single mussel being seven. No significant difference in microplastic particles per mussel was observed among the different sites sampled. A significant positive relationship between particles per mussel and size of upstream catchment was observed, but a relationship between particles per mussel and percentage of urban land use was not observed.

Microplastic Prevalence in 4 Oregon Rivers Along a Rural to Urban Gradient Applying a Cost‐Effective Validation Technique

Microplastics are ubiquitous in our environment and are found in rivers, streams, oceans, and even tap water. Riverine microplastics are relatively understudied compared with those in marine ecosystems. In Oregon (USA), we sampled 8 sites along 4 freshwater rivers spanning rural to urban areas to quantify microplastics. Plankton tow samples from sites along the Columbia, Willamette, Deschutes, and Rogue Rivers were analyzed using traditional light microscopy for initial microplastic counts. Application of Nile Red dye to validate microplastics improved microplastic identification, particularly for particles (Wilcox test; p = 0.001). Nile Red-corrected microfiber abundance was correlated with human population within 5 km of the sample site (R² = 0.554), although no such relationship was observed between microparticles and population (R² = 0.183). We found that plastics were present in all samples from all sites, despite the range from undeveloped, remote stretches of river in rural areas to metropolitan sites within Portland (OR, USA), demonstrating the pervasive presence of plastic pollution in freshwater ecosystems. Environ Toxicol Chem 2020;39:1590-1598. © 2020 SETAC.

Ecotoxicity of polystyrene microplastics to submerged carnivorous Utricularia vulgaris plants in freshwater ecosystems

Much attention is currently paid to microplastic (MP) pollution, particularly in marine systems. There is increasing concern regarding the potential toxicity of MPs to organisms at the physiological and morphological levels. However, little is known about the impact of MPs on aquatic life, despite their ubiquitous presence in freshwater ecosystems. In this study, the aquatic plant Utricularia vulgaris was exposed to 1, 2 and 5 μm polystyrene fluorescent MP particles at concentrations of 15, 70 and 140 mg/L for 7 days. The toxic effects of MPs on the growth rate and morphological and physiological characteristics of U. vulgaris were assessed. The results showed that the relative growth rates and the functional traits of leaves (morphological and photosynthetic) were significantly inhibited at a high concentration of MP particles (140 mg/L) when compared to the control group. The impacts on growth performance were likely due to bioaccumulation of MPs in the bladders, as shown by confocal microscopy. Furthermore, the antioxidative enzyme activities showed that high concentrations of MPs induce high ecotoxicity and oxidative damage to U. vulgaris. Thus, U. vulgaris has the potential to be an excellent bioindicator of MP pollution in freshwater ecosystems and should further be applied in ecological risk assessments of the effects of MPs on higher aquatic plants.