Microplastics are ubiquitous pollutants in aquatic habitats and commonly found in the gut contents of fish yet relatively little is known about the retention of these particles by fish. In this ...study, goldfish were fed a commercial fish food pellet amended with 50 particles of one of two microplastics types, microbeads and microfibers. Microbeads were obtained from a commercial facial cleanser while microfibers were obtained from washed synthetic textile. Following consumption of the amended pellet, fish were allowed to feed to satiation on non-amended food followed by fasting for periods ranging from 1.5 h to 6 days. Fish sacrificed at different time points were dissected to remove gut contents and the digesta contents retention and microplastic retention was determined. Although a small number of microplastic particles were retained in fish GI-tracts after 6 days (0–3 particles/50), the retention of microplastics was generally similar to the retention of bulk digesta contents. According to a breakpoint regression model fitted to digesta contents and microplastic particles, the 50% and 90% evacuation times were 10 h and 33.4 h, respectively. The results of this study indicate that neither microbeads nor microfibers are likely to accumulate within the gut contents of fish over successive meals.
•Microplastic retention in goldfish was not significantly different from digesta.•Microbeads and microfibers exhibited similar gut transit and retention times.•The 90% retention time for microplastics in fish GI-tracts was 33.4 h.
Diet assimilation efficiencies (AEs) of polychlorinated biphenyls (PCBs) absorbed to microplastics and food were determined in goldfish (Carassius auratus). Microplastics were spiked with 14 ...environmentally rare PCBs and incorporated into fish pellets previously spiked with a technical PCB mixture (Aroclor 1254). Five diet treatments were created having microplastic contents of 0, 5, 10, 15, 20, and 25% and fed to fish within 24 h of the diet creation. Fish from each treatment were fed a microplastic amended food pellet and PCB AEs were determined by mass balance. Microplastic-associated PCBs had lower AEs (geomean 13.36%) compared to food matrix-associated PCBs (geomean 51.64%). There were interactions between PCB AEs and the microplastic content of the diet. PCBs affiliated with microplastics became more bioavailable with increasing microplastic content of food while food matrix-associated PCB bioavailability declined when microplastic contents exceeded 5%. Despite controlling for microplastic-food contact time, there was some evidence for redistribution of lower K OW food matrix-associated PCBs onto microplastics causing a decrease in their AE relative to nonplastic and low plastic containing diets. The low bioavailability of microplastic-associated PCBs observed in the present study provides further support to indicate that microplastics are unlikely to increase POPs bioaccumulation by fish in aquatic systems.
The objective of this study was to characterize commercially-available cotton fabrics to determine their suitability as materials for construction of cloth masks for personal and public use to reduce ...infectious disease spread. The study focused on cottons because of their widespread availability, moderate performance and they are recommended for inclusion in home-made masks by international health authorities. Fifty-two cottons were analyzed by electron microscopy to determine fabric characteristics and fabric weights. Sixteen fabrics were selected to test for breathability and to construct 2-ply cotton masks of a standard design to use in quantitative fit testing on a human participant. Cotton mask fitted filtration efficiencies (FFEs) for 0.02-1 μm ambient and aerosolized sodium chloride particles ranged from 40 to 66% compared with the mean medical mask FFE of 55±2%. Pressure differentials across 2-ply materials ranged from 0.57 to > 12 mm H2O/cm2 on samples of equal surface area with 6 of 16 materials exceeding the recommended medical mask limit. Models were calibrated to predict 2-ply cotton mask FFEs and differential pressures for each fabric based on pore characteristics and fabric weight. Models indicated cotton fabrics from 6 of 9 consumer categories can produce cloth masks with adequate breathability and FFEs equivalent to a medical mask: T-shirt, fashion fabric, mass-market quilting cotton, home décor fabric, bed sheets and high-quality quilting cotton. Masks from one cloth mask and the medical mask were re-tested with a mask fitter to distinguish filtration from leakage. The fabric and medical masks had 3.7% and 41.8% leakage, respectively. These results indicate a well fitted 2-ply cotton mask with overhead ties can perform similarly to a disposable 3-ply medical mask on ear loops due primarily to the superior fit of the cloth mask which compensates for its lower material filtration efficiency.
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•Interspecies interactions and system stability to norfloxacin (NOR) were analyzed.•Without grazers, NOR decreased colony size and relative abundance of C. vulgaris.•With grazers, NOR ...decreased colony size and dominance of Scenedesmus species.•With and without grazers, NOR reduced stability of S. obliquus-C. vulgaris system.
Despite recent advances in assessing lethal effects of antibiotics on freshwater organisms, little is known about their potential consequences on community composition and function, which are essential for assessing the ecological risk of these pollutants. Here, we investigated the impact of norfloxacin (NOR) on the short-term (≤ 6 days) dynamics of co-cultured Scenedesmusquadricauda-Chlorella vulgaris and Scenedesmusobliquus-C. vulgaris, and the long-term (≤ 70 days) dynamics of co-cultured S.obliquus-C. vulgaris in experiments with or without grazer Daphnia magna at sublethal antibiotic concentrations (0, 0.5, 2 and 8 mg L-1). NOR increased the relative abundance of Scenedesmus species in the absence of grazers but exerted opposite effects when Daphnia was present in both short- and long-term experiments due to reduced colony size. Meanwhile, increasing NOR concentrations led to quickly increased total algal density in the initial stage, followed by a sharp decline in the long-term experiment in the absence of grazers; when Daphnia was present, population fluctuations were even larger for both prey and predator species (e.g., grazer extinction at the highest concentration). Thus, NOR affected the outcome of species interactions and decreased temporal stability of plankton ecosystems, suggesting that antibiotics have more extensive impacts than presently recognized.
The ability of headwater bed and suspended sediments to mitigate non-point agricultural phosphorus (P) loads to the lower Great Lakes is recognized, but the specific biogeochemical processes ...promoting sediment P retention or internal P release remain poorly understood. To elucidate these mechanisms, three headwater segments located within priority watersheds of Southern Ontario, Canada, were sampled through the growing season of 2018–2020. The study employed equilibrium P assays along with novel assessments of legacy watershed nutrients, nitrogen (N) concentrations, sediment redox, and microbial community composition. 20-year data revealed elevated total P (TP) and total Nitrogen (TN) at an inorganic fertilizer and manure fertilizer-impacted site, respectively. Overall, sampled sites acted as P sinks; however, agricultural sediments exhibited significantly lower buffering capacity compared to a reference forested watershed. Collection of fine suspended sediment (<63 µm) through time-integrated sampling showed the suspended load at the inorganic-fertilized site was saturated with P, indicating a greater potential for P release into surface waters compared to bed sediments. Through vertical microsensor profiling and DNA sequencing of the sediment microbial community, site-specific factors associated with a distinct P-source event were identified. These included rapid depletion of dissolved oxygen (DO) across the sediment water interface (SWI), as well as the presence of nitrate-reducing bacterial and ammonia-oxidizing archaeal (AOA) genera. This research provides valuable insights into the dynamics of P in headwaters, shedding light on P retention and release. Understanding these processes is crucial for effective management strategies aimed at mitigating P pollution to the lower Great Lakes.
Biota samples from the Vancouver municipal landfill located in Delta, BC, Canada, have some of the highest polybrominated diphenyl ether (PBDE) levels reported from North America. We followed a ...population of European starlings (Sturnus vulgaris) breeding in a remediated area in the landfill to identify exposure routes and bioaccumulation of PBDEs in a simple terrestrial food chain. This population was compared to a reference farm site located 40 km east in Glen Valley. We analyzed samples of European starling eggs and nestling livers as well as invertebrate prey species consumed by starlings for PBDE concentrations. We also collected soil samples from starling foraging areas. All samples from the Delta landfill had higher PBDE congener concentrations compared to the Glen Valley reference site and were dominated by BDE-99 and BDE-47. Stable nitrogen (δ N15) and carbon (δ C13) isotope analysis of starling blood samples and provisioned invertebrates revealed that stable δC13 signatures differed between the sites indicating that the diet of starlings in the Delta landfill included a component of human refuse. Biota-soil accumulation factors (BSAFs) > 1 demonstrated that PBDEs were bioaccumulating in soil invertebrates, particularly earthworms, which were readily accessible to foraging starlings in the landfill. Biomagnification factors (BMFs) calculated from foraged food items and starling egg and liver samples were >1, indicating that a diet of soil invertebrates and refuse contributed substantially to the PBDE exposure of local starlings.
•BDE concentrations were higher in starling eggs and chicks from an urban landfill than a rural farm.•Human refuse and soil invertebrates were dominant dietary sources of BDE exposure to starlings at the landfill.•BSAFs for BDE-47, -99, −100, and −154 were >1 indicating bioaccumulation in earthworms and refuse at the landfill.•BMFs for BDE-47, -99, −100, −153, and −154 were >1 indicating biomagnification in starlings from their diet.
As a result of historical industrial activity, the sediments in the inner harbor of Owen Sound Bay in the northeastern part of Lake Huron in Ontario, Canada are contaminated with organic compounds. ...The present study showed that the concentrations of Ʃ PAH16-EPA in all sediments in the inner harbor were above the sediment quality guidelines for the province of Ontario, Canada, with mean Ʃ PAH16-EPA concentrations at the most contaminated site of 46,000 μg/kg dry weight. The concentrations of polychlorinated biphenyls, brominated diphenyl ethers, and organochlorine compounds were all below sediment quality guidelines. The patterns of PAH and alkyl-PAH compounds in sediment cores indicated that contamination is from mixed sources, with a strong indication of pyrogenic contamination from industries that used to operate in the area, including a coal gasification plant. Other areas of the bay are impacted by petrogenic contamination, potentially from spills of fuel. The even distribution of PAH and alkyl-PAH compounds throughout core profiles at depths up to 25 cm indicates that this is a dynamic system and contaminated sediments are not being covered by deposition of less contaminated sediments. This study illustrates the value of determining the patterns of both PAH and alkyl-PAH compounds in sediments for regulatory purposes and also for forensic source tracking.
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•Gross contamination was observed in an embayment of the Laurentian Great Lakes.•Very high concentrations of PAHs and alkyl-PAHs were detected in sediments.•Sources of PAHs and alkyl-PAHs were linked to industrial pyrogenic contamination.
Batch equilibrium phosphorus concentration (EPC
0
) methods were applied to determine phosphorus capacity of sediments from three agriculturally influenced tributaries in southern Ontario – Belle ...River, Big Creek, and Nissouri Creek. Aliquots of sediments were amended with soluble reactive phosphorus and incubated at four temperatures (5, 15, 25, and 35°C). Batches of sediments from each location and temperature were also subjected to a treatment; gamma (γ)-irradiated at 28 kGy over 24-h (sterilized) and compared to non-sterilized biotic samples. Treatment showed a significant effect on EPC
0
in Belle River and Nissouri Creek but non-significant effect in Big Creek. Temperature showed a significant effect in Belle River, Nissouri Creek, and the biotic subset of Big Creek. While direction of shift was not consistent in all cases, the biotic subsets of all three locations showed a significant effect of temperature.
This study evaluated the dependence of mercury (Hg) elimination by fish on species specific fish metabolic rate in order to generate improved algorithms of Hg elimination rate coefficients. Mercury ...elimination rate coefficient observations were collected by literature review and fish routine metabolic rate (RMR) estimates calculated using the Wisconsin Fish Bioenergetics Model. Three models were compared that considered body weight, temperature, thermal category, Hg depuration period and RMR as predictors of Hg elimination. The best performing model incorporated body size, temperature and fish thermal category, explaining 79% of the variation of the calibration data and between 20% and 69% of the variation of validation data sets. The results support the conclusion that species-specific differences in metabolic rate influence mercury elimination by fish but also highlight major data gaps in the mercury toxicokinetic literature necessary to develop robust models Hg elimination by fish.
Purpose
Assessing the physicochemical characteristics of the stream suspended sediment phase (SSP) is a common component of watershed monitoring, whereas the biological attributes of the SSP are more ...rarely described. The microbial component is valuable to sediment apportionment studies and can inform on pathogen transport and in-stream biogeochemistry.
Methods
An established passive, flow-through sampling technique (Phillips Tube (PT) Sampler) was used for time-integrated evaluation of suspended phase microbial communities within an agricultural stream segment (≈ 0.7 km) in southern Ontario, Canada. Monthly DNA-metabarcoding of the SSP was conducted and contrasted with bed sediment phases (BSPs).
Results
PT samplers showed good spatial precision. Monthly sampled bed sediment microbial communities showed more similarity to each other than to suspended sediment communities. Suspended sediments were characterized by aerobic/facultative aerobic taxa with bed sediments defined by nitrate, iron, and sulfate metabolizing groups. Greater community diversity was observed in BSP samples, with biomarker analysis identifying more unique genera in SSP samples. In situ dissolved oxygen (DO) logging revealed a substantial decrease in PT sampler DO (12 to 3 mg L
−1
) after 3 weeks of deployment. Precipitation events caused in-stream DO concentrations to flatline temporarily, but increased concentrations within samplers.
Conclusions
PT samplers collected adequate sediment volumes for microbial DNA metabarcoding and showed good replicability. Use of samplers during higher flow periods may collect a more representative microbial community that is less affected by within-sampler decreases in DO. Future use of PT samplers should consider microbial/redox effects that can alter in situ chemistries.
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