Low‐cost microplastic visualization in feeding experiments using an ultraviolet light‐emitting flashlight

Abstract

Microplastics are pollutants threatening the health of marine, freshwater and terrestrial organisms. To analyze whether an organism is able to ingest microplastics, the organism is usually fed with expensive fluorescent microbeads and placed under a fluorescence microscope for microplastic detection. However, such equipment cannot be afforded by many laboratories. Therefore, we developed a low-cost method to study the ingestion and egestion of low-cost, fluorescent microplastic fragments and fibers by aquatic invertebrates. During our feeding experiments, we exposed the freshwater snail Radix balthica to artificial biofilms containing 15% microplastic fragments and fibers, respectively. We then used an ultraviolet (UV) flashlight to irradiate the microplastics. Hence, we could directly observe the microplastics in the food, during ingestion and egestion as well as in the snail feces. Our method, thereby, allowed us to analyze the snails' behavior (during ingestion and egestion), the microplastics' distribution in the snail feces and the microplastics' shape after the snails' digestion. Furthermore, we observed that the snails ceased to egest microplastics after 76 hr following microplastic ingestion. However, chemical digestion of the snails 6 days after microplastic exposure revealed that microplastics were still present in R. balthica, emphasizing the microplastics' persistence in the animals' bodies. This is the first study combining the usage of low-cost fluorescent microplastics with an inexpensive UV flashlight for microplastic detection during microplastic ingestion and egestion by living organisms. Our new method is not only cost-effective, but also fast and can be performed by a wide range of researchers without special previous training. K E Y W O R D Saffordability, black light, gastrointestinal passage, gastropods, synthetic polymers

Ingestion and Depuration of Microplastics by a Planktivorous Coral Reef Fish, Pomacentrus amboinensis

“…In terms of suitable species, controlled exposure studies specifically examining ingestion and depuration kinetics rarely consider organisms likely exposed to and contaminated with microplastics in the marine environment. For example, ingestion and depuration studies have mainly focused on aquatic invertebrates (Wang X. et al, 2019;Chae and An, 2020;Ehlers et al, 2020), and freshwater fish (Grigorakis et al, 2017;Xiong et al, 2019;Hoang and Felix-Kim, 2020). In contrast, only four ingestion and depuration studies have been conducted on brackish/marine fish (Manabe et al, 2011;Cong et al, 2019;Bour et al, 2020b) despite these being some of the most frequently reported organisms contaminated with microplastics (Lusher, 2015;Kroon F. J. et al, 2018;Jensen et al, 2019).…”

Proposal for an initial screening method for identifying microplastics in marine sediments

“…Currently, low-cost and easy detection methods to study the accumulation of microplastics in the environment are available 37 . A tracing method that can be used to visualize fluorescent microplastics using a general industrial ultraviolet flashlight has been reported 38 . However, it can only detect a limited number of microplastic types and cannot be used to identify nonfluorescent microplastics in the environment.…”

Microplastic fiber diet—Fiber-supplemented pellets for small fish

“…The main challenges to overcome when handling microplastic fibers in the laboratory are exclusion of other airborne fibers, difficulties in weighing and counting the thin and irregular shaped fibers, and production of a homogeneous distribution of fibers in water and other matrices. Only a small number of studies were published so far that conducted exposure experiments with microplastic fibers provided via the diet [6 , 8 , 9 , 11 , 13] . While for gastropods and crustaceans inclusion of fibers in a biofilm or gelatinous matrix is possible, dietary pellets that contain microplastic fibers are more suitable for fish.…”