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1. A fish tale: a century of museum specimens reveal increasing microplastic concentrations in freshwater fish

   https://doi.org/10.1002/eap.2320  

   Hou, Loren; McMahan, Caleb D.; McNeish, Rae E.; Munno, Keenan; Rochman, Chelsea M.; Hoellein, Timothy J. (April 2021, Ecological Applications)

   Abstract Plastic is pervasive in modern economies and ecosystems. Freshwater fish ingest microplastics (i.e., particles <5 mm), but no studies have examined historical patterns of their microplastic consumption. Measuring the patterns of microplastic pollution in the past is critical for predicting future trends and for understanding the relationship between plastics in fish and the environment. We measured microplastics in digestive tissues of specimens collected from the years 1900–2017 and preserved in museum collections. We collected new fish specimens in 2018, along with water and sediment samples. We selected four species:Micropterus salmoides(largemouth bass),Notropis stramineus(sand shiner),Ictalurus punctatus(channel catfish), andNeogobius melanostomus(round goby) because each was well represented in museum collections, are locally abundant, and collected from urban habitats. For each individual, we dissected the digestive tissue from esophagus to anus, subjected tissue to peroxide oxidation, examined particles under a dissecting microscope, and used Raman spectroscopy to characterize the particles' chemical composition. No microplastics were detected in any fish prior to 1950. From mid‐century to 2018, microplastic concentrations showed a significant increase when data from all fish were considered together. All detected particles were fibers, and represented plastic polymers (e.g., polyester) along with mixtures of natural and synthetic textiles. For the specimens collected in 2018, microplastics in fish and sediment showed similar patterns across study sites, while water column microplastics showed no differences among locations. Overall, plastic pollution in common freshwater fish species is increasing and pervasive across individuals and species, and is likely related to changes in environmental concentrations. Museum specimens are an overlooked source for assessing historical patterns of microplastic pollution, and for predicting future trends in freshwater fish, thereby helping to sustain the health of commercial and recreational fisheries worldwide. 

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2. The global odyssey of plastic pollution

   https://doi.org/10.1126/science.abc4428  

   Rochman, Chelsea M.; Hoellein, Timothy (June 2020, Science)

   Scientists who once studied microplastics (plastic debris <5 mm in size) as ocean pollutants have now detected them in soils, biota, and Earth's atmosphere. To decipher the global fate of microplastics, scientists have begun to ask questions about the “microplastic cycle,” which is akin to global biogeochemical cycles (nitrogen, carbon, and water). For example, what are the sources of microplastics, and how do they transform as they move from one pool (e.g., a beach, inside an organism, or a river bed) to another? And what processes (“fluxes”) transfer microplastics between pools? On page 1257 of this issue, Brahney et al. ( 1 ) report high-resolution spatial and temporal data that provide evidence of both global and regional microplastic transport, thus increasing our understanding of the microplastic cycle. 

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3. Reporting Guidelines to Increase the Reproducibility and Comparability of Research on Microplastics

   https://doi.org/10.1177/0003702820930292  

   Cowger, Win; Booth, Andy M.; Hamilton, Bonnie M.; Thaysen, Clara; Primpke, Sebastian; Munno, Keenan; Lusher, Amy L.; Dehaut, Alexandre; Vaz, Vitor P.; Liboiron, Max; et al (May 2020, Applied Spectroscopy)

   The ubiquitous pollution of the environment with microplastics, a diverse suite of contaminants, is of growing concern for science and currently receives considerable public, political, and academic attention. The potential impact of microplastics in the environment has prompted a great deal of research in recent years. Many diverse methods have been developed to answer different questions about microplastic pollution, from sources, transport, and fate in the environment, and about effects on humans and wildlife. These methods are often insufficiently described, making studies neither comparable nor reproducible. The proliferation of new microplastic investigations and cross-study syntheses to answer larger scale questions are hampered. This diverse group of 23 researchers think these issues can begin to be overcome through the adoption of a set of reporting guidelines. This collaboration was created using an open science framework that we detail for future use. Here, we suggest harmonized reporting guidelines for microplastic studies in environmental and laboratory settings through all steps of a typical study, including best practices for reporting materials, quality assurance/quality control, data, field sampling, sample preparation, microplastic identification, microplastic categorization, microplastic quantification, and considerations for toxicology studies. We developed three easy to use documents, a detailed document, a checklist, and a mind map, that can be used to reference the reporting guidelines quickly. We intend that these reporting guidelines support the annotation, dissemination, interpretation, reviewing, and synthesis of microplastic research. Through open access licensing (CC BY 4.0), these documents aim to increase the validity, reproducibility, and comparability of studies in this field for the benefit of the global community. 

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4. Filtration Methods for Microplastic Removal in Wastewater Streams — A Review

   https://doi.org/10.1142/S0129156423500192  

   Salahuddin, U.; Sun, J.; Zhu, C.; Gao, P. (December 2023, International Journal of High Speed Electronics and Systems)

   Microplastics are commonly recognized as environmental and biotic contaminants. The prevalent presence of microplastics in aquatic settings raises concerns about plastic pollution. Therefore, it is critical to develop methods that can eliminate these microplastics with low cost and high effectiveness. This review concisely provides an overview of various methods and technologies for removing microplastics from wastewater and marine environments. Dynamic membranes and membrane bioreactors are effective in removing microplastics from wastewater. Chemical methods such as coagulation and sedimentation, electrocoagulation, and sol-gel reactions can also be used for microplastic removal. Biological methods such as the use of microorganisms and fungi are also effective for microplastic degradation. Advanced filtration technologies like a combination of membrane bioreactor and activated sludge method show high microplastic removal efficiency. 

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5. Egestion rates of microplastic fibres in fish scaled to in situ concentration and fish density

   https://doi.org/10.1111/fwb.14007  

   Hou, Loren; McNeish, Rachel; Hoellein, Timothy J. (January 2023, Freshwater Biology)

   Abstract Microplastics (particles <5 mm) are commonly found in aquatic organisms across taxonomic groups and ecosystems. However, the egestion rate of microplastics from aquatic organisms and how egestion rates compare to other rates of microplastic movement in the environment are sparsely documented. We fed microplastic fibres to round gobies ( Neogobius melanostomus ), an abundant, invasive species in the Laurentian Great Lakes. We conducted two trials where round gobies were fed microplastic‐containing food either a single time (1 day) or every day over 7 days. There was no difference in microplastic egestion rates from the 1 day or 7 day feeding trials, suggesting no impact of duration of exposure on egestion (exponential decay rate = −0.055 [±0.016 SE ] and −0.040 [±0.007 SE ], respectively). Turnover time of microplastics (i.e., average time from ingestion to egestion) in the gut ranged from 18.2 to 25.0 hr, similar to published values for other freshwater taxa. We also measured microplastics in the digestive tracts of round gobies collected directly from Lake Michigan, U.S.A. Using published values for round goby density and microplastic concentration at the study sites, we calculated areal egestion rate by round gobies (no. particles m –2  day –1 ), and compared it to riverine microplastic export (no. particles m –2  day –1 ). Both area‐based rates were of the same order of magnitude, suggesting that round goby egestion could be an important, and potentially overlooked component of microplastic dynamics at the ecosystem scale. Animal egestion is well‐known as a major component of nutrient and carbon cycling. However, direct measurements of microplastic fluxes in the environment that include animal egestion rates are uncommon. An ecosystem ecology approach is needed to meet the emerging challenge of generating microplastic budgets for freshwater environments and elsewhere, thereby informing management and mitigation of plastic pollution at a global scale. 

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