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Digestible Fluorescent Coatings for Cumulative Quantification of Microplastic Ingestion Evan G. Karakolis, Brian Nguyen, Jae Bem You, Percival J. Graham, Chelsea M. Rochman, and David Sinton Environ. Sci. Technol. Lett., Just Accepted Manuscript • DOI: 10.1021/acs.estlett.7b00545 • Publication Date (Web): 26 Dec 2017 Downloaded from http://pubs.acs.org on December 27, 2017
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Environmental Science & Technology Letters
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Digestible Fluorescent Coatings for Cumulative Quantification of Microplastic Ingestion
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Evan G Karakolisa#, Brian Nguyena#, Jae Bem You a, Percival J Grahama, Chelsea M Rochmanb and David
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Sintona*
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a
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#
Equally contributing author
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*
Corresponding author
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Department of Mechanical and Industrial Engineering and Institute for Sustainable Energy, University of Toronto, 5 King’s College Road, Toronto, ON, Canada, M5S 3G8. b Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks St, Toronto, ON, Canada, M5S 3B2
*E-mail:
[email protected]. Tel: +1 (416) 978-1623 (David Sinton).
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ABSTRACT: The ubiquitous presence of microplastics in the environment makes it imperative to understand
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their effects. In particular, we must understand exposure – i.e., how many microplastics are ingested by
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organisms. This has proved difficult because counting microplastics in an organism’s gut content provides only a
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snapshot in time. Here, we show a method that uses a digestible fluorescent coating (DFC) to quantify cumulative
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microplastic ingestion. Our method enables precise and automated enumeration of cumulative microplastic
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ingestion with the flexibility to track different microplastic types and sizes with distinct fluorescent tracers. We
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confirm the coating is not acutely toxic and is not preferentially ingested by several invertebrate species. This
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method provides a unique and reliable approach to quantify cumulative microplastic ingestion in laboratory
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exposure studies, and can be used to advance our understanding of the impact of microplastics to wildlife.
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INTRODUCTION
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Emissions of plastic waste to aquatic1,2 and terrestrial3 ecosystems is a growing concern. In particular,
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microplastics (particles < 5 mm in size) are recognized as a global concern4,5, and have been extensively studied
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in recent years. Microplastics interact with a wide range of organisms6,7 either directly, via dermal contact or
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ingestion8, or indirectly, via trophic transfer9 (where microplastics outside of an organism’s typical prey size are
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consumed because they have been previously ingested by or attached to their typical prey). Their impact on
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ecosystems can be twofold. Microplastics can adhere to, and be ingested by, organisms, and have the potential to
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cause harmful physical effects including internal abrasions and blockages, translocation throughout the body and
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inflammation2. Microplastics can also be a source of hazardous chemicals from their production10 or via sorption
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of priority pollutants11,12, and a source of microorganisms13. To fully assess the impact that microplastics will have
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on biota, it is critical to be able to measure exposure, including the amount of microplastics that are ingested.
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While existing enumeration techniques, counting microplastics in the gut and/or feces or subsampling the exposure water
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, determine the amount of plastics ingested at a given time point, they are not easily 1 ACS Paragon Plus Environment
Environmental Science & Technology Letters
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adaptable to accurately quantify cumulative ingestion. Furthermore, current methods that use visual sorting of the
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entire contents of an exposure vessel to identify plastics in fecal pellets for a cumulative measure suffers from key
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limitations: (1) microplastics that pass through the digestive tract without being encased in a fecal pellet are not
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counted; (2) microplastics on the surface of animals or fecal pellets can be misidentified as ingested; and (3)
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manually identifying and counting is labor intensive, operator-dependent and susceptible to error, particularly for
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studies with smaller organisms (
