Microplastics in the gastrointestinal tracts of fish and the water from an urban prairie creek
Abstract
Microplastics are defined as any plastic with a diameter ≤5 mm. Problems associated with these plastics such as contamination of both marine and freshwater environments and ingestion by aquatic organisms are of increasing concern. Our study quantifies the number of microplastics in a prairie creek immediately downstream of Regina, Saskatchewan, Canada. Water samples and five species of fish were collected from sample sites upstream and downstream of a wastewater treatment plant (WWTP) in the summers of 2015 and 2016. Samples were digested in either a Fe(II)/H2O2 or NaClO solution and observed under a microscope where plastics present were enumerated by colour and type. At least one microplastic was detected in 73.5% of fish and 95.6% of water samples, showing that the creek does, in fact, contain microplastics. Concentrations were higher in water from upstream sites, likely due to dilution of creek water by the release of treated effluent. The results of this study provide baseline conditions for the presence of plastics in the creek prior to a major upgrade of the WWTP scheduled for completion in 2016.
Introduction
The contamination of both marine and freshwater environments with microplastics, as well as their ingestion by freshwater organisms, is of increasing concern (Wagner et al. 2014; Eerkes-Medrano et al. 2015). Although no ubiquitous definition of microplastics exists, microplastics are largely considered to be plastic polymer debris with a diameter of ≤5 mm (Betts 2008; Barnes et al. 2009). This plastic debris can be ranked as primary, in which the particle was manufactured as a microplastic, or secondary, in which the particle was manufactured as a macroplastic (>5 mm) and degraded to its present size (Cole et al. 2011; Rummel 2014). Primary microplastics largely consist of microbeads (tiny round plastics mainly used as abrasive scrubs) and are commonly found in hygiene, sandblasting, and medical products (Zitko and Hanlon 1991; Patel et al. 2009; Browne et al. 2011; Rochman et al. 2015). Secondary microplastics vary in form and origin, and often result from the breakdown of macroplastics through ultraviolet, microbial, and physical degradation (Browne et al. 2007; Rios et al. 2007; Moore 2008; Shah et al. 2008; Barnes et al. 2009; Ryan et al. 2009; Andrady 2011). Further categorization includes grouping based on shape as beads, fibers, and fragments. Microplastic fibers can be primary or secondary in nature and mainly originate from items such as clothing, fishing nets, and plastic bags (Browne et al. 2011; Claessens et al. 2013; Hartline et al. 2016). Fragmented microplastics are secondary plastics often originating from plastic objects that do not fray into fibers (Browne et al. 2011; Cole et al. 2011; Claessens et al. 2013; Mathalon and Hill 2014).
Microplastics can easily disperse in aquatic ecosystems due to their ubiquitous nature and buoyant properties (Cole et al. 2011; Wright et al. 2013). Many polymers that formulate microplastics have slightly lower densities than water, and this combined with their small size and relatively large surface area to volume ratio engenders microplastics’ neutral buoyancies (Cole et al. 2011). This allows them to drift over great distances within aquatic currents or over vast expanses of land by wind (Cole et al. 2011; Mathalon and Hill 2014). Neutral buoyancy also contributes to their similar appearance to small aquatic organisms such as plankton. Plastic formulations that are denser than water tend to sink into the sediments (Ryan 2015). In addition, aggregates of microplastics and organic material such as biofilms may sink and contribute to the sequestration of microplastics in sediments (Teuten et al. 2009; Cole et al. 2011; Long et al. 2015; Fazey and Ryan 2016). In turn, microplastics may be ingested, either actively (e.g., by pelagic fish consuming them as they would plankton) or passively (e.g., benthic fish consuming them inadvertently when feeding in sediments). Once consumed, problems such as pseudo-satiation, blockage of the intestine, endocrine disruption through leached plasticizers, and contamination by adhered persistent organic pollutants can arise (Barnes et al. 2009; Talsness et al. 2009; Teuten et al. 2009; Lithner et al. 2011; Wright et al. 2013). Microplastics can end up being re-suspended due to bioturbation in the sediments, which facilitates cycles of ingestion, excretion, and settlement (Wright et al. 2013).
Although the majority of work to date has examined plastics in marine systems, studies showing prevalence in freshwaters have been increasing in numbers. Plastics in freshwaters were originally observed in the Laurentian Great Lakes (Eriksen et al. 2013); numerous studies since have detected microplastics in other freshwater systems. For example, the Global Water Research Coalition 2015 (GWRC 2016) summarized the extent of microplastic freshwater pollution and showed that European and North American rivers contain as many as 387 particles·m−3 (McCormick et al. 2014; Lechner and Ramler 2015).
Earlier studies found microplastics in the influent of wastewater treatment plants (WWTPs) from both household and industrial operations. These plastics may be removed during primary phase separation treatment as well as lost to settling in aeration pond sediments during secondary treatment (Carr et al. 2016; Murphy et al. 2016); however, microplastics may pass through the treatment system and be released in treated effluent (Gregory 1996; Browne et al. 2007; Fendall and Sewell 2009). Small numbers per litre released in effluent can translate to large numbers of plastics in aquatic systems, considering the large volumes of treated effluent released from WWTPs worldwide. As a result, studies have shown that wastewater effluent is a source of microplastics to aquatic systems (see reviews in Estahbanati and Fahrenfeld 2016; Ziajahromi et al. 2016).
Our objective to determine if microplastics were present in the water and fish in Wascana Creek was supplemented by the examination of microplastics upstream and downstream of the City of Regina WWTP. The city of Regina WWTP services ∼200 000 people resulting in the release of between 73 and 81 million L·day−1 during the months we sampled. Until fall 2016, wastewater was treated at the Regina plant by phase separation in primary sedimentation vessels, followed by secondary treatment in aerated settling lagoons, phosphorous removal by the addition of aluminum salts, and UV disinfection prior to release into Wascana Creek (Razban 2010). We hypothesized that because phase separation likely allowed for the removal of microplastics and microplastics were likely sequestered in settling ponds due to the production of phytoplankton and biofilm-microplastic aggregates heavy enough to sink to lagoon sediments (Long et al. 2015; Carr et al. 2016; Fazey and Ryan 2016; Murphy et al. 2016), concentrations of microplastics would not differ upstream and downstream of the WWTP. To our knowledge, no one has examined the prevalence of microplastics in the water and fish in a northern prairie system (Anderson et al. 2016), thus our examination of microplastics in an urban creek downstream of Regina, Saskatchewan, Canada adds to a growing body of evidence that supports the ubiquitous nature of microplastics in freshwater systems.
Methods
Site selection
Three sampling sites were selected along Wascana Creek located on the northern outskirts of Regina in south-central Saskatchewan and sampled in July 2015 and July and August 2016 (Fig. 1). Wascana Creek is fed by Wascana Lake, a water storage system in the center of the city of Regina constructed in the late 1880s. There are no major population centers upstream of Regina. This area has a warm summer continental climate with strong seasonality and severe winters (Köppen–Geiger classification: Dfb). From 1991 to 2010, daily mean temperatures ranged from a mean winter temperature of −14.7 °C in January to a mean summer temperature of 18.9 °C in July (Environment Canada 2016). Mean precipitation ranged from 0.5 mm in December to 70.9 mm in June (Environment Canada 2016). Three sites were chosen in relation to Regina’s WWTP Outflow (OF): ∼3 km upstream, at the OF, and ∼10 km downstream. Differences in weather at different sites were negligible. At the OF site, water was a mix of treated sewage and upstream water. There was no measurement to determine the proportion of each. The process in Regina’s WWTP during the study period consisted of primary sedimentation, secondary treatment via aerated lagoons, chemical flocculation in tertiary clarifiers, and UV disinfection prior to discharge (Razban 2010). In fall 2016, an upgraded WWTP went online, which uses bioreactors to treat wastewater.
Fig. 1.
Sample collection
Water
Five individual water samples were collected at each site using an 80 μm mesh conical net held in the center of the stream over a 5 min period in July 2015 and July and August 2016. In 2016, three were collected from each site in July, and due to weather concerns, two additional samples were collected in August. As there was no statistically significant difference in concentrations in July compared with August, we combined the data from those two dates. Flow was measured concurrently using a Swaffer© Flow Meter. The particulates accumulated on the net were rinsed off with creek water into a glass jar and stored at 4 °C until analysis. Water conductivity (μS·cm−1), pH, temperature (°C), and dissolved oxygen (%) were measured using a YSI 556 multiprobe sonde. Discharge of effluent records was obtained from the WWTP operators, EPCOR Prairie Water.
Fish
Target fish species were collected using seine nets, gill nets, conventional tackle, and minnow traps in June 2015. Five species of fish were collected: northern pike (Esox lucius), white sucker (Catostomus commersoni), emerald shiner (Notropis atherinoides), fathead minnow (Pimephales promelas), and five-spine stickleback (Eucalia inconstans). The majority of the samples were caught with seine net tows performed between two opposing gill nets to ensure any fish in that area would be caught using one of the two methods. Gill nets were set along the creek at intervals of approximately 10 m and were checked and reset every 30 min. Minnow traps and conventional tackle were baited with dog food and leeches, respectively. Euthanization of fish was done using buffered tricaine methane/sulfonate (MS-222) as outlined by procedures approved by the Canadian Council on Animal Care (2010). Appropriate permits and protocols for animal care were obtained from the University of Regina Animal Utilization Protocol 15-08. Fish were euthanized, sorted into Ziploc® bags based on species, and put on ice for transport. In total 75 emerald shiners, 30 northern pike, 32 white suckers, 34 fathead minnows, and 10 five-spine stickelbacks were collected. The population of fish within the creek system was not measured. Fish in this system swim throughout the entirety of the creek over the course of the open water season, dispersing downstream depending on water depth and temperature as the season progresses (A. McCutcheon and B. Skatfeld, personal communication, 2016).
Analysis
Water
For all preparation and digestion of samples, metal or glass vessels were used, and lab coats were worn to prevent contamination from clothing. Water samples were sieved using a stacked series (4750, 500, and 75 μm mesh size), and material from each sieve was rinsed into beakers with deionized water. Wet peroxide oxidation was used to dissolve all organic material present in the sample (Masura et al. 2015). Approximately 20 mL 0.05 M Fe(II)SO4·7 H2O solution and ∼20 mL 30% hydrogen peroxide (H2O2) were added slowly and left to react for 5 min (Masura et al. 2015). This mixture was heated to 75 °C on a hot plate until bubbling, removed to cool, and then returned to the hot plate to further digest for 30 min. Additional H2O2 was added as needed in 20 mL increments to dissolve all organic material (Masura et al. 2015). After the digestion, samples were sieved, rinsed into glass Petri dishes, and left to dry overnight in an oven at 100 °C. Samples were covered with glass watch glasses and glass Petri dish tops during digestion and drying, respectively. Once dry, the samples were examined under a dissection microscope, and microplastics were visually enumerated and characterized by their size, shape, and colour. Suspected plastics were then confirmed to be plastic using hot needle testing, which involved the application of a heated needle tip to each plastic to confirm that it would melt. Although characterization using Raman spectroscopy would have been helpful in identifying the nature of the plastics, budgets did not allow this. In 2016, samples were treated with added conditions that included filtering all reagents and rinse water before use and completing all tasks inside a positive pressure laminar hood. The purpose of these added conditions was to reduce contamination by transparent, colourless (hereafter referred to as clear) fibers that occurred in the laboratory (see below); similar methods were used by Luscher et al. (2013).
Fish
Entire gastrointestinal (GI) tracts were removed from each fish by creating an incision just below the throat and carefully cutting down the ventral side of the fish to the anal opening. Samples were stored in ethanol until digestion using 10% NaClO solution (diluted with deionized water in a 1:3 v/v ratio) (Collard et al. 2015). Intact GI tracts from specimens smaller than 5.0 g were digested completely after being cut into small pieces with dissection scissors. In specimens larger than 5.0 g, GI tracts were cut open and rinsed with ethanol prior to the filtration process due to the thicker digestive epithelium. The rinsate along with the storage ethanol was filtered using a 5.0 micron polycarbonate membrane filter and glass filter train into a Teflon bomb to digest overnight allowing digestion of organic material. A subsequent 5 min digestion in ∼30 mL HNO3:NaClO (1:10 v/v) solution was performed if organic material was still evident after initial digestion, as it often was with the larger GI tracts (Collard et al. 2015).
After digestion, samples were filtered on 5.0 micron polycarbonate membrane filters, and particulates were rinsed onto glass Petri dishes with 95% methanol. Samples were dried in an oven at 100 °C overnight to allow the methanol to evaporate. It is important to note that methanol is extremely flammable and alternative methods of drying are encouraged. Once the samples were dry, enumeration of microplastics was performed under a dissection microscope as described above.
Statistical analysis
Shapiro–Wilk’s tests were used to confirm that both fish and water data were normally distributed. Two-factor analysis of variances (ANOVAs) (without replication) were completed to compare the mean numbers and concentrations of microplastics in water collected at three sites in 2015 and 2016. Because fish move among sites, we did not test site-to-site differences in fish. However, we did test species differences using Kruskal–Wallis’ one-way ANOVA on ranks and subsequent Tukey’s pairwise multiple comparison.
Issues of contamination
Microplastics are very lightweight and mobile, and therefore, caution must be used while analyzing samples to guarantee that no particles from the air or water in the laboratory contaminate the samples (Mathalon and Hill 2014; Masura et al. 2015). We noticed in initial samples that there were a large number of clear plastic fibers inside and outside of the glass Petri plates. We measured microplastics in a series of blanks and found that limiting access to unfiltered air (by working in a positive pressure hood) and plastic (by the use of glass and metal equipment) and using filtered reagents reduced the contaminant microplastics (Tables S1 and S2). It should be noted that the clear fibers that were contaminants in the actual samples were impossible to distinguish from the clear fibers that were non-contaminants from the creek itself, and as such we removed all clear fibers from the results of the study.
Results and discussion
Microplastics in water
Microplastics of varying shapes and colours were found in water at all sites in both 2015 and 2016 (Tables S3 and S4). Concentrations of microplastics were significantly higher at upstream sites (3.8 ± 1.2 and 7.7 ± 2.0 microplastics·m−3 in 2015 and 2016, respectively) compared with those at the WWTP OF (1.0 ± 0.2 and 1.0 ± 0.4 microplastics·m−3 in 2015 and 2016, respectively) and farther downstream (3.7 ± 0.3 and 0.9 ± 0.3 microplastics·m−3 in 2015 and 2016, respectively; F 1,2 = 8.45, p = 0.002) and in 2016 compared with 2015 (F 1,1 = 14.65, p < 0.001; Fig. 2). The concentrations of microplastics in water were confounded by a statistical interaction between year sampled and site collected (F 1,2 = 6.61, p = 0.005), and while we are cautious in interpreting the main effects due to the interaction effect, it is likely that the interaction effect is due to the fact that the concentrations were greater upstream in both years and flow rates differed between years (Table 1).
Fig. 2.
Table 1.
| Sample site | Sample number | Year | Flow rate (m·s−1) | Sample time (s) | Volume of water sampled (m3) |
|---|---|---|---|---|---|
| Upstream | 1–5 | 2015 | 0.36 | 300 | 5022.00 |
| WWTP OF | 1–5 | 2015 | 0.86 | 300 | 11 997.00 |
| Downstream | 1–5 | 2015 | 0.22 | 300 | 3069.00 |
| Upstream | 1–3 | 2016 | 0.11 | 300 | 1559.05 |
| WWTP OF | 1–3 | 2016 | 0.44 | 300 | 6096.15 |
| Downstream | 1–3 | 2016 | 2.00 | 300 | 27 927.90 |
| Upstream | 4–5 | 2016 | 0.16 | 300 | 2268.27 |
| WWTP OF | 4–5 | 2016 | 0.27 | 300 | 3826.49 |
| Downstream | 4–5 | 2016 | 5.04 | 300 | 70 299.07 |
Note: WWTP OF, wastewater treatment plant outflow.
The reduction of concentrations from the upstream site suggests possible sequestration within, or loss from, the creek. Sequestration and loss could have occurred via wind removal, burial in sediments and near shore vegetation, as well as via ingestion by organisms as they travelled downstream (Gregory 1996; Browne et al. 2007; Fendall and Sewell 2009; Cole et al. 2011; Mathalon and Hill 2014). However, if concentrations decreased as we moved downstream due to only loss, we would have expected to observe a further decrease in concentrations at the downstream site. This was not the case; concentrations were lowest at the WWTP, suggesting that the release of treated water from the WWTP could have potentially increased flow rates, thus increasing the dilution of microplastics in our samples. In addition, year-to-year differences in flow rates of the creek could have been due to differing precipitation rates. Discharge of effluent records for the dates of sampling showed that between 24.1 and 77.4 million L of effluent were released to the creek on our sampling days (77.4, 77.3, and 24.1 million L on 22 July 2015, 18 July 2016, and 17 August 2016, respectively); volumes high enough to have caused a dilution effect on concentrations. Therefore, differences in concentrations with sampling site are likely a combination of settling and dilution. There is also the possibility that the concentrations at the downstream site represented a contribution of microplastics from the WWTP combined with a decrease in concentrations due to settling. Our work provides no solid evidence to suggest that the WWTP aided in either eliminating or adding microplastics to Wascana Creek.
These results are similar to other studies of rivers, with a few key differences in the type and quantity of microplastics observed. Baldwin et al. (2016) sampled 29 tributaries to the Great Lakes and found between 0.5 and 32 microplastics·m−3. Concentrations of most types of plastics were higher in areas with more urban runoff, although fiber concentrations did not change with this parameter (Baldwin et al. 2016). In California, Moore et al. (2005) found considerably higher concentrations (average = 30–109 microplastics·m−3) in water samples from the Los Angeles River than in our samples from Wascana Creek. This is likely due to a higher population in the Los Angeles River catchment area compared with that surrounding Wascana Creek, as well as the fact that Moore et al. (2005) examined concentrations in rivers after heavy precipitation and related runoff events. Studies have found that microplastic concentrations increased after storms, suggesting that rainwater may re-suspend plastics previously sequestered in the sediments as well as wash plastics present in riparian areas into the aquatic system (Lattin et al. 2004; Baldwin et al. 2016). In other sites in California (Coyote Creek and San Gabriel rivers (Moore et al. 2005), and Santa Monica Bay (Lattin et al. 2004)), concentrations were more similar to ours with average values ranging from <1 to 22 microplastics·m−3 depending on the proximity to the shore line.
Microplastics found in fish GI tracts
Of 181 fish sampled, 73.5% had between 1 and 20 microplastics in their GI tracts, ranging from 50.0% (fathead minnows) to 83.3% (northern pike; Fig. 3A). There was a significant difference in the number of microplastics found among species, with northern pike having significantly more compared with other species of fish (H = 16.487, p = 0.002; Fig. 3B). These percentages may be explained by differences in the feeding habits of the various species. For example, benthivores, such as white suckers, fathead minnows, and sticklebacks, are likely exposed to microplastics that have settled onto the sediments, whereas planktivores such as shiners would be more likely to consume microplastics suspended in the water column. We did not see a significant difference in the number of microplastics in benthivorous and planktivorous fish. We did observe significantly more plastics in northern pike, and because microplastics have been shown to accumulate in the GI tracts of many organisms, it is reasonable to hypothesize that, as apex predators, pike may have increased concentrations due to trophic transfer from the smaller species (Brillant and MacDonald 2000; Browne et al. 2008). In addition to the clear, loose fibers that we classified as contamination in both water and fish samples, we observed clear fibers bunched into balls in the fish GI tracts. Although due to the nature of consolidation of these fibers, we suspect that these were not contamination, we were conservative and removed these from our data set. The large balls of clear fibers were found in many of the northern pike stomachs. Although we cannot speculate if these were indeed consumed plastics, it is worth noting that ∼15.0% of northern pike contained these fibers.
Fig. 3.
The majority of the northern pike were caught at the upstream site, and the majority of emerald shiners were caught at the downstream site, with none at the upstream site. The majority of fish move upstream in the spring to spawn, dispursing once the water depths allow them to move back downstream (A. McCutcheon and B. Skatfeld, personal communication, 2016). Because the fish are moving throughout the system, we could not analyze site-to-site differences.
There have been very few reports of microplastics in freshwater fish. The prevalence of fish containing microplastics in our study was considerably higher than the earliest reports examining microplastics in wild freshwater fish. Sanchez et al. (2014) observed microplastics in GI tracts of 12% of wild gudgeons (Gobio gobio) from French rivers, slightly lower values compared with Biginagwaa et al. (2016) who observed plastics in 20% of both Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) in Lake Victoria, Africa, whereas Fazey and Ryan (2016) observed microplastics in the guts of 45% of two species of freshwater sunfish in a Texan river. Our values were similar to those of Silva-Cavalcanti et al. (2017) who found microplastics in the GI tracts of 83% of the freshwater catfish species Hoplosternum littorale in South America. However, we caution the comparison with microplastics in fish in other studies due to the fact that feeding behaviours influence exposure to microplastics (Wright et al. 2013; Setälä et al. 2014). As the literature on microplastics in freshwater fish becomes more robust, comparison of microplastics in fish with similar feeding habits in different aquatic systems will become increasingly possible.
Types of microplastics
The majority of microplastics found in both the water and the fish GI tracts were fibers and fragments (Table 2), similar to other studies examining microplastics in mussels, water, sediments, and fish (Luscher et al. 2013; Free et al. 2014; Mathalon and Hill 2014; Baldwin et al. 2016). Water samples were dominated by fibers (89.5%), with a lesser proportion of fragments (10.2%) and less than 1% beads (Table 2). The low values of microbeads found in the water were surprising. We speculate that microbeads are proportionally more prevalent in wastewater influent due to household and industrial waste as the source of these plastics, and that due to extended water retention times in aerobic settling ponds the microbeads were sequestered in the WWTP works.
Table 2.
| Water samples | Fish GI tracts | |||
|---|---|---|---|---|
| Microplastic type | Total number | Meannumber per sample | Total number | Meannumber per sample |
| Fragments | 61 | 1.39 ± 0.34 | 186 | 1.40 ± 0.22 |
| Fibers | 536 | 12.48 ± 2.46 | 208 | 1.56 ± 0.14 |
| Beads | 2 | 0.05 ± 0.03 | 42 | 0.32 ± 0.06 |
Note: Data from water samples collected in 2015 and 2016 have been combined. GI, gastrointestinal.
We observed similar proportions of fibers (47.7%) and fragments (42.6%) in fish GI tracts. The proportion of fragments in the fish GI tracts was four times higher than the proportion in water. We speculate that this suggested selective uptake of fragments could be due to benthic feeding habits exposing fish to fragments sequestered in sediments. The proportion of fibers in fish GI tracts were similar to those reported by Silva-Cavalcanti et al. (2017), who observed 47% fibers in South American catfish, and Jabeen et al. (2017), who found between 57% and 88% in six species of freshwater fish in China. The vast majority of microplastics in the guts of sunfish from a river in central Texas were threads (96%) (Fazey and Ryan 2016). Again, we caution the comparison of results among fish with different feeding habits.
Earlier studies found plastic types termed “foams and films” (Luscher et al. 2013; Free et al. 2014); however, nothing of this class was found in our study. This may also explain variation in the proportion of fibers and fragments found in our study. Free et al. (2014) found mainly fragments in water samples; however, they were looking at a remote mountain lake, not a small creek receiving treated wastewater. This distinction is important because the location and source of microplastic pollution have a direct effect on the concentrations of microplastics in the water body (Browne et al. 2011; Cole et al. 2011; Free et al. 2014). Fibers tend to be lightweight and can stay suspended in the water column for longer periods of time than the denser fragments and beads. Different locations will contain different microplastic types depending on the original sources of plastics (Cole et al. 2011; Wright et al. 2013). Further research is needed to determine the origin of the microplastics in our system.
Our study used very conservative methods to deal with contamination by clear fibers. We ran statistical analysis on both the water and fish data including the clear fibers to determine if the exclusion of the clear fibers influenced our conclusions. With the water data, test results were consistent between the two data sets. For the fish data, significant differences among species were lost when the tests were run including the clear fibers.
Conclusions
Three types of microplastics were observed in both water and fish in Wascana Creek. Although all five species of fish were found to have microplastics in their GI tracts, northern pike had significantly higher values than emerald shiners and fathead minnows. On the whole, this study shows that microplastics are present in Wascana Creek, and that further studies will be required to determine the source of the microplastics, the habits of the organisms ingesting the microplastics, the toxicants absorbed and emitted by the microplastics, and methods for remediation that may help diminish microplastic numbers in the creek. Although jurisdictions that have instigated bans on microbeads in personal products are to be commended, our research suggests that plastic fibers may be more prevalent in freshwater systems, suggesting that a reduction of plastic use needs to be more comprehensive than banning microbeads in personal care products.
Our hypothesis that concentrations of microplastics would be similar in downstream compared with upstream sites due to sequestration in the WWTP was not supported, in part because of the unexpected high concentrations found at the upstream site. Although we showed that concentrations downstream of the WWTP were not elevated, suggesting that the WWTP was not a large source of microplastics, our study design could not determine if site-to-site differences were due to losses in the creek or dilution of plastics due to WWTP effluent. Further studies should examine microplastics in treated effluent directly.
In late summer 2016, Regina’s WWTP was upgraded to a modern system using bioreactive processes. As a result, settling ponds became obsolete and were taken offline. Using the previous system, wastewater was sequestered in settling ponds for weeks to months which may have allowed sufficient time for biofilms to form on plastics leading to the sequestration of plastics in lagoon sediments. In the new system, the residence time of wastewater in the treatment plant has been significantly reduced, thus creating the potential to reduce sequestration of plastics in sediment lagoons. Now that the upgraded WWTP is fully operational, we suggest that this study be repeated to determine if reduced processing time has resulted in increased concentrations of microplastics downstream of the WWTP.
Acknowledgements
This work was supported by the Saskatchewan Fish and Wildlife Development Fund. We thank Drs. R Manzon, P Leavitt, and K Finlay for providing laboratory and field equipment and J Dickenson, T Blampied, C McCowan, and L Whitehouse for their help in sample collection. K Gallant from EPCOR Water Prairies provided discharge records, and E Joyce provided netting material for blanks. A McCutcheon and B Skatfeld, Saskatchewan Ministry of Environment, provided information about the extent of fish swimming in the creek during open water season.
References
Anderson JC, Park BJ, and Palace VP. 2016. Microplastics in aquatic environments: Implications for Canadian ecosystems. Environmental Pollution, 218: 269–280.
Andrady AL. 2011. Microplastics in the marine environment. Marine Pollution Bulletin, 62: 1596–1605.
Baldwin AK, Corsi SR, and Mason SA. 2016. Plastic debris in 29 Great Lakes tributaries: Relations to watershed attributes and hydrology. Environmental Science & Technology, 50: 10377–10385.
Barnes DK, Galgani F, Thompson RC, and Barlaz M. 2009. Accumulation and fragmentation of plastic debris in global environments. Philosophical Transactions of the Royal Society B: Biological Sciences, 364: 1985–1998.
Betts K. 2008. Why small plastic particles may pose a big problem in the oceans. Environmental Science & Technology, 42: 8995.
Biginagwaa FJ, Mayomaa BS, Shashouad Y, Syberga K, and Khan FR. 2016. First evidence of microplastics in the African Great Lakes: recovery from Lake Victoria Nile perch and Nile tilapia. Journal of Great Lakes Research, 42: 146–149.
Brillant M, and MacDonald B. 2000. Postingestive selection in the sea scallop, Placopecten magellanicus (Gmelin): the role of particle size and density. Journal of Experimental Marine Biology and Ecology, 253: 211–227.
Browne MA, Galloway T, and Thompson R. 2007. Microplastic—an emerging contaminant of potential concern? Integrated Environmental Assessment and Management, 3: 559–561.
Browne MA, Dissanayake A, Galloway TS, Lowe DM, and Thompson RC. 2008. Ingested microscopic plastic translocates to the circulatory system of the mussel, Mytilus edulis (L.). Environmental Science & Technology, 42: 5026–5031.
Browne MA, Crump P, Niven SJ, Teuten E, Tonkin A, Galloway T, et al. 2011. Accumulation of microplastic on shorelines worldwide: sources and sinks. Environmental Science & Technology, 45: 9175–9179.
Canadian Council on Animal Care. 2010. Guide to the care and use of experimental animals [online]: Available from ccac.ca/en_/standards/guidelines.
Carr SA, Liu J, and Tesoro AG. 2016. Transport and fate of microplastic particles in wastewater treatment plants. Water Research, 91: 174–182.
Claessens M, Van Cauwenberghe L, Vandegehuchte MB, and Janssen C. 2013. New techniques for the detection of microplastics in sediments and field collected organisms. Marine Pollution Bulletin, 70: 227–233.
Cole M, Lindeque P, Halsband C, and Galloway TS. 2011. Microplastics as contaminants in the marine environment: a review. Marine Pollution Bulletin, 62: 2588–2597.
Collard F, Gilbert B, Eppe G, Parmentier E, and Das K. 2015. Detection of anthropogenic particles in fish stomachs: an isolation method adapted to identification by Raman spectroscopy. Archives of Environmental Contamination and Toxicology, 69: 331–339.
Eerkes-Medrano D, Thompson RC, and Aldridge DC. 2015. Microplastics in freshwater systems: a review of the emerging threats, identification of knowledge gaps and prioritisation of research needs. Water Research, 75: 63–82.
Environment Canada. 2016. Canadian Climate Normals 1981–2010 [online]: Available from climate.weather.gc.ca/climate_normals/results_1981_2010_e.html?searchType=stnProv&lstProvince=SK&txtCentralLatMin=0&txtCentralLatSec=0&txtCentralLongMin=0&txtCentralLongSec=0&stnID=3002&dispBack=0.
Eriksen M, Mason S, Wilson S, Box C, Zellers A, Edwards W, et al. 2013. Microplastic pollution in the surface waters of the Laurentian Great Lakes. Marine Pollution Bulletin, 77: 177–182.
Estahbanati S, and Fahrenfeld NL. 2016. Influence of wastewater treatment plant discharges on microplastic concentrations in surface water. Chemosphere, 162: 277–284.
Fazey FMC, and Ryan PG. 2016. Biofouling on buoyant marine plastics: an experimental study into the effect of size on surface longevity. Environmental Pollution, 210: 354–360.
Fendall LS, and Sewell MA. 2009. Contributing to marine pollution by washing your face: microplastics in facial cleansers. Marine Pollution Bulletin, 58: 1225–1228.
Free C, Jensen O, Mason S, Eriksen M, Williamson N, and Boldgiv B. 2014. High-levels of microplastic pollution in a large, remote, mountain lake. Marine Pollution Bulletin, 85: 156–163.
Gregory M. 1996. Plastic ‘scrubbers’ in hand cleansers: a further (and minor) source for marine pollution identified. Marine Pollution Bulletin, 32: 867–871.
GWRC. 2016. Global Water Research Coalition [online]: Available from globalwaterresearchcoalition.net/.
Hartline NL, Bruce NJ, Karba SN, Ruff EO, Sonar SU, and Holden PA. 2016. Microfiber masses recovered from conventional machine washing of new or aged garments. Environmental Science & Technology, 50: 11532–11538.
Jabeen K, Su L, Li J, Yang D, Tong C, Mu J, et al. 2017. Microplastics and mesoplastics in fish from coastal and fresh waters of China. Environmental Pollution, 221: 141–149.
Lattin G, Moore C, Zellers A, Moore S, and Weisberg S. 2004. A comparison of neustonic plastic and zooplankton at different depths near the southern California shore. Marine Pollution Bulletin, 49: 291–294.
Lechner A, and Ramler D. 2015. The discharge of certain amounts of industrial microplastic from a production plant into the River Danube is permitted by the Austrian legislation. Environmental Pollution, 200: 159–160.
Lithner D, Larsson Å, and Dave G. 2011. Environmental and health hazard ranking and assessment of plastic polymers based on chemical composition. Science of the Total Environment, 409: 3309–3324.
Long M, Moriceau B, Gallinari M, Lambert C, Huvet A, Raffray J, et al. 2015. Interactions between microplastics and phytoplankton aggregates: Impact on their respective fates. Marine Chemistry, 175: 39–46.
Luscher A, McHugh M, and Thompson R. 2013. Occurrence of microplastics in the gastrointestinal tract of pelagic and demersal fish from the English Channel. Marine Pollution Bulletin, 67: 94–99.
Masura J, Baker J, Foster G, Arthur C, and Herring C. 2015. Laboratory methods for the analysis of microplastics in the marine environment: recommendations for quantifying synthetic particles in waters and sediments NOAA Technical Memorandum, NOS-OR&R-48.
Mathalon A, and Hill P. 2014. Microplastic fibers in the intertidal ecosystem surrounding Halifax Harbor, Nova Scotia. Marine Pollution Bulletin, 81: 69–79.
McCormick A, Hoellein TJ, Mason SA, Schluep J, and Kelly JJ. 2014. Microplastic is an abundant and distinct microbial habitat in an urban river. Environmental Science & Technology, 48: 11863–11871.
Moore CJ. 2008. Synthetic polymers in the marine environment: a rapidly increasing, long-term threat. Environmental Research, 108: 131–139.
Moore CJ, Lattin GL, and Zellers AF. 2005. Working our way upstream: a snapshot of land-based contributions of plastic and other trash to Coastal Waters and Beaches of Southern California. Algalita Marine Research Foundation, Long Beach, California.
Murphy F, Ewins C, Carbonnier F, and Quinn B. 2016. Wastewater treatment works (WwTW) as a source of microplastics in the aquatic environment. Environmental Science & Technology, 50: 5800–5808.
Patel M, Goyal B, Bhadada S, Bhatt J, and Amin A. 2009. Getting into the brain: approaches to enhance brain drug delivery. CNS Drugs, 23: 35–58.
Razban B. 2010. Novel protocols for the identification of significant bacterial consormial activities in the City of Regina aerobic wastewater treatment plant. MASc, University of Regina, Regina, Saskatchewan. 87 p.
Rios LM, Moore C, and Jones PR. 2007. Persistent organic pollutants carried by synthetic polymers in the ocean environment. Marine Pollution Bulletin, 54: 1230–1237.
Rochman C, Kross S, Armstrong J, Bogan M, Darling E, Green S, et al. 2015. Scientific evidence supports a ban on microbeads. Environmental Science & Technology, 49: 10759–10761.
Rummel C. 2014. Occurrence and potential effects of plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea. Johannes Gutenberg-Universität Mainz, Mainz, Germany.
Ryan PG. 2015. Does size and buoyancy affect the long-distance transport of floating debris? Environmental Research Letters, 10: 084019.
Ryan P, Moore C, van Franeker J, and Moloney C. 2009. Monitoring the abundance of plastic debris in the marine environment. Philosophical Transactions of the Royal Society B: Biological Sciences, 364: 1999–2012.
Sanchez W, Bender C, and Porcher JM. 2014. Wild gudgeons (Gobio gobio) from French rivers are contaminated by microplastics: preliminary study and first evidence. Environmental Research, 128: 98–100.
Setälä O, Fleming-Lehtinen V, and Lehtiniemi M. 2014. Ingestion and transfer of microplastics in the planktonic food web. Environmental Pollution, 185: 77–83.
Shah AA, Hasan F, Hameed A, and Ahmed S. 2008. Biological degradation of plastics: a comprehensive review. Biotechnology Advances, 26: 246–265.
Silva-Cavalcanti JS, Silva JDB, de França EJ, de Araújo MCB, and Gusmão F. 2017. Microplastics ingestion by a common tropical freshwater fishing resource. Environmental Pollution, 221: 218–226.
Talsness CE, Andrade AJM, Kuriyama SN, Taylor J, and vom Saal FS. 2009. Components of plastic: experimental studies in animals and relevance for human health. Philosophical Transactions of the Royal Society B: Biological Sciences, 364: 2079–2096.
Teuten EL, Saquing JM, Knappe DRU, Barlaz MA, Jonsson S, Björn A, et al. 2009. Transport and release of chemicals from plastics to the environment and to wildlife. Philosophical Transactions of the Royal Society B: Biological Sciences, 364: 2027–2045.
Wagner M, Engwall M, and Hollert H. 2014. Editorial: (micro)plastics and the environment. Environmental Sciences Europe, 26: 16–18.
Wright SL, Thompson RC, and Galloway TS. 2013. The physical impacts of microplastics on marine organisms: a review. Environmental Pollution, 178: 483–492.
Ziajahromi S, Neale PA, and Leusch FDL. 2016. Wastewater treatment plant effluent as a source of microplastics: review of the fate, chemical interactions and potential risks to aquatic organisms. Water Science and Technology, 74: 2253–2269.
Zitko V, and Hanlon M. 1991. Another source of pollution by plastics: skin cleansers with plastic scrubbers. Marine Pollution Bulletin, 22: 41–42.
Supplementary material
Supplementary Material 1 (DOCX / 76.6 KB):
- Download
- 76.64 KB
Information & Authors
Information
Published In
FACETS
Volume 2 • Number 1 • January 2017
Pages: 395 - 409
Editor: Daniel Schindler
History
Received: 19 January 2017
Accepted: 24 March 2017
Version of record online: 2 May 2017
Copyright
© 2017 Campbell et al. This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
Data Availability Statement
All relevant data are within the paper and in the Supplementary Material.
Key Words
Sections
Subjects
Authors
Author Contributions
PRW and BDH conceived and designed the study.
SHC and PRW performed the experiments/collected the data.
SHC and BDH analyzed and interpreted the data.
BDH contributed resources.
SHC and BDH drafted or revised the manuscript.
Competing Interests
The authors have declared that no competing interests exist.
Metrics & Citations
Metrics
Other Metrics
Citations
Cite As
Samantha H. Campbell, Patrick R. Williamson, and Britt D. Hall. 2017. Microplastics in the gastrointestinal tracts of fish and the water from an urban prairie creek. FACETS.
2: 395-409.
https://doi.org/10.1139/facets-2017-0008
Export Citations
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.
Cited by
1. Observation and visual identification of microplastics
2. Microplastics contamination in marine system
3. Characteristics, Contamination Levels, and Ecosystem Risk Assessment of Microplastics in Surface Water of a Highly Urbanized River from a Developing Country
4. Microplastic Chemostasis and Homogeneity During a Historic Flood on the Mississippi River
5. Microplastics in Farmed Animals—A Review
6. Microplastic-contamination in the flesh and gastrointestinal tract of nile tilapia (Oreochromis niloticus) reared in floating net cages at lake Ranu Grati, Pasuruan, East Java, Indonesia
7. Rhamnetin abrogates polystyrene microplastics prompted hepatic damage by regulating Nrf-2/Keap-1 pathway
8. The entrainment of polyester microfibers modifies the structure and function of periphytic biofilms
9. Microplastics pollution in tropical lakes: water, zooplankton, and fish in Central Mexico
10. A state of the art-mini review on the sources, contamination, analysis, and consequences of microplastics in water
11. Peculiarities of Microplastic Accumulation in Fish and Crustaceans of the Mekong Delta (Vietnam)
12. Microplastic Content in the Gastrointestinal Tract of Some Fish Species of Lake Kubenskoe (Vologda Oblast)
13. From source to sink: part 1—characterization and Lagrangian tracking of riverine microplastics in the Mediterranean Basin
14. Ecological assessment of microplastic contamination in surface water and commercially important edible fishes off Kadalundi estuary, Southwest coast of India
15. Microplastic Occurrences in Freshwater Fish of Bangladesh
16. Emerging pollutant in surface water bodies: a review on monitoring, analysis, mitigation measures and removal technologies of micro-plastics
17. Occurrence of microplastics in commercial fishes from aquatic ecosystems of northern Poland
18. Understanding microplastic pollution of marine ecosystem: a review
19. Assessment of Microplastics and Potentially Toxic Elements in Surface Sediments of the River Kelvin, Central Scotland, United Kingdom
20. Peculiarities of Microplastic Accumulation in Fish and Crustaceans of the Mekong Delta (Vietnam)
21. Microplastic Content in the Gastrointestinal Tract of Some Fish Species of Lake Kubenskoe (Vologda Oblast)
22. Do’s and don’ts of microplastic research: a comprehensive guide
23. Microplastics abundance, distribution and composition in surface waters, sediments and fish species from Amir˗Kalayeh Wetland, Northern Iran
24. Microplastics in complex soil matrix: Recovery, identification and removal using micro nano techniques
25. Extensive Microplastic Contamination in Southeastern Florida Forage Fishes
26. Pharmacotherapeutic potential of ginkgetin against polystyrene microplastics–instigated testicular toxicity in rats: A biochemical, spermatological, and histopathological assessment
27. Long-term investigation of microplastic abundance in Squalius species in Turkish inland waters
28. Current perspectives, challenges, and future directions in the electrochemical detection of microplastics
29. Examining the Environmental Concerns Caused by the Microplastic Contamination in Marine Ecosystem
30. Microplastics in Soils and Sediments
31. Effects of microplastics on amphibian performance and survival: Current knowledge and research gaps
32. The first evidence of microplastic presence in the River Nile in Khartoum, Sudan: Using Nile Tilapia fish as a bio-indicator
33. Anthropocene airborne microfibers: Physicochemical characteristics, identification methods and health impacts
34. Characteristics of microplastics in Dusky-tailed cardinalfish (
Taeniamia macroptera
) from natural reef and Fish Apartment in Pasir Putih Situbondo, East Java, Indonesia
35. Microplastic Contamination in Vertical Water Columns and Fish: A Comparative Study between the Buriganga River and the Bay of Bengal in Bangladesh
36. Discovering the High Risk of Fragmented Microplastics: A Study on Indoor Dust Microplastics in the Greater Bay Area of China
37. Microplastics pollution in rice fields: a case study of Pir Bazar rural district of Gilan, Iran
38. Impacts of microplastic on fisheries and seafood security — Global analysis and synthesis
39. Disperse dyes, temperature and yarn parametre's effect on microfibre shedding of polyester spun yarn
40. Hot or not: systematic review and laboratory evaluation of the hot needle test for microplastic identification
41. Responses of Mytilus galloprovincialis in a Multi-Stressor Scenario: Effects of an Invasive Seaweed Exudate and Microplastic Pollution under Ocean Warming
42. Ecological traits do not predict the uptake of microplastics by fishes in a Neotropical River
43. Hepatoprotective effects of astragalin against polystyrene microplastics induced hepatic damage in male albino rats by modulating Nrf-2/Keap-1 pathway
44. Prevalence of microplastics in commonly consumed fish species of the river Old Brahmaputra, Bangladesh
45. Abundance and characteristics of microplastics in a freshwater river in northwestern Himalayas, India - Scenario of riverbank solid waste disposal sites
46. Distribution characteristics of microplastics and corresponding feeding habits of the dominant shrimps in the rivers of Chongming Island
47. Litter per liter – Lakes' morphology and shoreline urbanization index as factors of microplastic pollution: Study of 30 lakes in NE Poland
48. Characterization and Removal of Microplastics in Landfill Leachate Treatment Plants in Istanbul, Turkey
49. Pinostrobin alleviates testicular and spermatological damage induced by polystyrene microplastics in adult albino rats
50. Microfibers in the gut of invasive armored catfish (Pterygoplichthys spp.) (Actinopterygii: Siluriformes: Loricariidae) in an urban lake in the floodplain of the Grijalva River basin, Mexico
51. Ecological traits do not predict the uptake of microplastics by fishes in a Neotropical River
52. Ingestion of microplastics in commercially important species along Thoothukudi coast, south east India
53. Exploring microplastic pollution in a Mediterranean river: The role of introduced species as bioindicators
54. Microplastics Detected in Sediments and Rocks Substrate of Marine Areas with Ghost Nets
55. Screening for Microplastic Uptake in an Urbanized Freshwater Ecosystem: Chondrostoma nasus (Linnaeus, 1758) Case Study
56. A fit‐for‐purpose categorization scheme for microplastic morphologies
57. Investigating the fate and transport of microplastics in a lagoon wastewater treatment system using a multimedia model approach
58. Microplastics in fishes in amazon riverine beaches: Influence of feeding mode and distance to urban settlements
59. Rhamnetin alleviates polystyrene microplastics-induced testicular damage by restoring biochemical, steroidogenic, hormonal, apoptotic, inflammatory, spermatogenic and histological profile in male albino rats
60. Aquatic Eco‐systems Under Influence of Climate Change and Anthropogenic Activities
61. Characterization and implication of microplastics on riverine population of the River Ravi, Lahore, Pakistan
62. Microplastics menace: the new emerging lurking environmental issue, a review on sampling and quantification in aquatic environments
63. Microplastic abundances in co-occurring marine mussels: species and spatial differences
64. Occurrence of Microplastics in Riverine Fishes Sold for Human Consumption in Chhattisgarh, India
65. Microplastics in fish and sediments from the Montenegrin coast (Adriatic Sea): Similarities in accumulation
66. Factors influencing the variation of microplastic uptake in demersal fishes from the upper Thames River Ontario
67. Environmental Pollution in Belgium and Implications for Aquatic Health
68. Contamination of microplastics, surface morphology and risk assessment in beaches along the Thoothukudi coast, Gulf of Mannar region
69. Microplastic loads within riverine fishes and macroinvertebrates are not predictable from ecological or morphological characteristics
70. Distinct microplastic patterns in the sediment and biota of an urban stream
71. Microplastics in Sediments of Southwest Caspian Sea: Characteristics, Distribution and Seasonal Variability
72. Spatial and temporal variations of microplastic concentrations in Portland's freshwater ecosystems
73. Microplastics in Eurasian otter (
Lutra lutra
) spraints and their potential as a biomonitoring tool in freshwater systems
74. Modelling the transfer and accumulation of microplastics in a riverine freshwater food web
75. Embryotoxicity of polystyrene microplastics in zebrafish Danio rerio
76. Sample preparation methods for the analysis of microplastics in freshwater ecosystems: a review
77. Dynamics of airborne microplastics, appraisal and distributional behaviour in atmosphere; a review
78. Quantification and Characterisation of Microplastics in Fish and Surface Water at Melayu River, Johor
79. Co-Exposure with an Invasive Seaweed Exudate Increases Toxicity of Polyamide Microplastics in the Marine Mussel Mytilus galloprovincialis
80. Introduction to the Analytical Methodologies for the Analysis of Microplastics
81. Microplastics in Biota
82. Airborne Microplastics
83. Occurrence of Microplastics in Freshwater
84. Occurrences and impacts of microplastics in soils and groundwater
85. Riverine biodiversity and importance: Potential threat and conservational challenges
86. Plastic pollution in marine and freshwater environments: abundance, sources, and mitigation
87. Spatial distribution of microplastics in Chinese freshwater ecosystem and impacts on food webs
88. Microplastic Loads within Riverine Fishes and Macroinvertebrates are Not Predictable from Ecological or Morphological Characteristics
89. Factors Influencing the Variation of Microplastic Uptake in Demersal Fishes from the Upper Thames River Ontario
90. Microplastic sampling techniques in freshwaters and sediments: a review
91. Microplastic pollution in soils and groundwater: Characteristics, analytical methods and impacts
92. Microplastic contamination assessment in water and economic fishes in different trophic guilds from an urban water supply reservoir after flooding
93. Microplastic in angling baits as a cryptic source of contamination in European freshwaters
94. Microplastic pollution in perch (Perca fluviatilis, Linnaeus 1758) from Italian south-alpine lakes
95. Origin, fate, and risk assessment of emerging contaminants in groundwater bodies: a holistic review
96. A novel method for organic matter removal from samples containing microplastics
97. Evidence of Microplastic Translocation in Wild-Caught Fish and Implications for Microplastic Accumulation Dynamics in Food Webs
98. Microplastic distribution in urban vs pristine mangroves: Using marine sponges as bioindicators of environmental pollution
99. The quantity and quality assessment of microplastics in the freshwater fishes: A systematic review and meta-analysis
100. Freshwater wild biota exposure to microplastics: A global perspective
101. Microplastics in different tissues of some commercially important fish species from Anzali Wetland in the Southwest Caspian Sea, Northern Iran
102. Microplastics in aquatic environments: A review on occurrence, distribution, toxic effects, and implications for human health
103. Preparation of biological samples for microplastic identification by Nile Red
104. Abundance, characteristics and variation of microplastics in different freshwater fish species from Bangladesh
105. Do Freshwater Fish Eat Microplastics? A Review with A Focus on Effects on Fish Health and Predictive Traits of MPs Ingestion
106. The missing ocean plastic sink: Gone with the rivers
107. Microplastic fibers — Underestimated threat to aquatic organisms?
108. Ecotoxicological and physiological risks of microplastics on fish and their possible mitigation measures
109. Microplastics contamination in food and beverages: Direct exposure to humans
110. Microplastics occurrence in the commercial Southeast Asian seafood and its impact on food safety and security: A review
111. Microplastics in freshwater fishes: Occurrence, impacts and future perspectives
112. Effects of Microplastics, Polystyrene, and Polyethylene on Antioxidants, Metabolic Enzymes, HSP-70, and Myostatin Expressions in the Giant River Prawn Macrobrachium rosenbergii: Impact on Survival and Growth
113. Presence and fate of microplastics in the water sources: focus on the role of wastewater and drinking water treatment plants
114. Microplastics and metal burdens in freshwater Tilapia (Oreochromis niloticus) of a metropolitan reservoir in Central Mexico: Potential threats for human health
115. Microplastic pollution in surface water and sediments in the urban section of the Vistula River (Poland)
116. Microplastics in wastewater treatment plants: Occurrence, fate and identification
117. Stable Isotope Insights into Microplastic Contamination within Freshwater Food Webs
118. Characterization of microplastics and anthropogenic fibers in surface waters of the North Saskatchewan River, Alberta, Canada
119. Airborne Microplastics
120. Microplastics in freshwater ecosystems: a recent review of occurrence, analysis, potential impacts, and research needs
121. Toward a unified framework for investigating micro(nano)plastics in packaged beverages intended for human consumption
122. Ingestion of microplastics by Hypanus guttatus stingrays in the Western Atlantic Ocean (Brazilian Amazon Coast)
123. Ecotoxicological Assessment of Microplastics in Freshwater Sources—A Review
124. Microplastics in brown trout (Salmo trutta Linnaeus, 1758) from an Irish riverine system
125. Distributions of Microplastics in Surface Water, Fish, and Sediment in the Vicinity of a Sewage Treatment Plant
126. Identification of microplastics in white wines capped with polyethylene stoppers using micro-Raman spectroscopy
127. Microplastic pollution in surface water of Lake Victoria
128. How can we trace microplastics in wastewater treatment plants: A review of the current knowledge on their analysis approaches
129. Microplastics in water, sediment and fish from the Fengshan River system: Relationship to aquatic factors and accumulation of polycyclic aromatic hydrocarbons by fish
130. Ingestion of Microplastic by Fish of Different Feeding Habits in Urbanized and Non-urbanized Streams in Southern Brazil
131. Microplastics as contaminants in freshwater environments: A multidisciplinary review
132. Microplastics in Freshwater Biota: A Critical Review of Isolation, Characterization, and Assessment Methods
133. Exposure to polystyrene microplastics causes reproductive toxicity through oxidative stress and activation of the p38 MAPK signaling pathway
134. Occurrence of microplastics in the Han River and riverine fish in South Korea
135. Effects of spatial and seasonal factors on the characteristics and carbonyl index of (micro)plastics in a sandy beach in Aveiro, Portugal
136. A novel approach to optically distinguish plastics based on fluorescence lifetime measurements
137. Finding Microplastics in Soils: A Review of Analytical Methods
138. Microplastic occurrence and effects in commercially harvested North American finfish and shellfish: Current knowledge and future directions
139. Microplastic prevalence in two fish species in two U.S. reservoirs
140. Occurrence, distribution and size relationships of plastic debris along shores and sediment of northern Lake Victoria
141. Occurrence and Ecotoxicological Effects of Microplastics on Aquatic and Terrestrial Ecosystems
142. Introduction to the Analytical Methodologies for the Analysis of Microplastics
143. Microplastics in Biota
144. Airborne Microplastics
145. “Down by the River”: (Micro-) Plastic Pollution of Running Freshwaters with Special Emphasis on the Austrian Danube
146. Microplastics in Freshwater Environments
147. Plastic Particle Ingestion by Wild Freshwater Fish: A Critical Review
148. Microplastics in the environment: A critical review of current understanding and identification of future research needs
149. A systematic study of the microplastic burden in freshwater fishes of south-western Germany - Are we searching at the right scale?
150. An Approach of Identifying Polymers With Fluorescence Lifetime Imaging
151. Microplastics biomonitoring in Australian urban wetlands using a common noxious fish (Gambusia holbrooki)
152. Emerging threats and persistent conservation challenges for freshwater biodiversity
153. Citizen science sampling programs as a technique for monitoring microplastic pollution: results, lessons learned and recommendations for working with volunteers for monitoring plastic pollution in freshwater ecosystems
154. Microplastic contamination in gudgeons (Gobio gobio) from Flemish rivers (Belgium)
155. Methods for sampling and detection of microplastics in water and sediment: A critical review
156. Microplastic hotspots in the Snake and Lower Columbia rivers: A journey from the Greater Yellowstone Ecosystem to the Pacific Ocean
157. Microplastics in the environment: Challenges in analytical chemistry - A review
158. Ecotoxicological effects of microplastics on biota: a review
159. The influence of exposure and physiology on microplastic ingestion by the freshwater fish Rutilus rutilus (roach) in the River Thames, UK
160. Are Nitric Acid (HNO3) Digestions Efficient in Isolating Microplastics from Juvenile Fish?