Plastic pollution has enormous impacts on freshwater and marine ecosystem health, and it is one of the topmost environmental concerns of the current geological period (i.e. the Anthropocene). Thus, the goal of our study was to provide baseline information and bridge the information gap on the occurrence of microplastics (MPs) in African freshwater systems, using two tributaries of the Gulf of Guinea (Ogun and Osun Rivers) in Nigeria as a case study and three freshwater insect species of different feeding guilds as bioindicators. A total of 29 individuals of the insect species were chemically digested and subsequently analysed for MP presence under a digital microscope and a micro-Fourier-transform infrared (μFTIR) spectroscope. Collector-gatherers (Chironomus sp. and Siphlonurus sp.) recorded the highest MP load per gram wet weight, while the predatory Lestes viridis recorded the lowest. The highest diversity of polymers was recorded in Chironomus sp. of Ogun River, i.e. styrene ethylene butylene styrene, acrylonitrile butadiene styrene (ABS), chlorinated polyethylene, polypropylene (PP), and polyester, while two polymers each were recorded in Siphlonurus sp. (i.e. polyester and ABS) and L. viridis (i.e. polyester and PP) of Osun River. We conclude that collector-gatherers like Chironomus sp. and Siphlonurus sp. could be best employed as MP bioindicators in freshwater systems. However, their suitability as MP bioindicators should be further investigated in different freshwater ecosystems worldwide.

Microplastic abundances have been studied intensively in the last years in marine and freshwater environments worldwide. Though several articles have been published about the Mediterranean Sea, only few studies about the Black Sea exist. The Black Sea drains into the Mediterranean Sea and may therefore significantly contribute to the Mediterranean marine pollution. So far, only very few articles have been published about micro-, meso- and macroplastic abundances in the Western Black Sea. In order to fill this knowledge gap and to decipher the number of plastics on the water surface, 12 samples were collected from surface waters with a neustonic net (mesh size 200 μm) in the Black Sea close to the Danube Delta and the Romanian shore. Organic matter was digested and plastic particles were isolated by density separation. The results of visual inspection, pyrolysis GC-MS (for microplastics) and ATR-FTIR (for mesoplastics >5 mm) revealed an average concentration of 7 plastic particles/m³, dominated by fibers (∼76%), followed by foils (∼13%) and fragments (∼11%). Only very few spherules were detected. The polymers polypropylene (PP) and polyethylene (PE) dominated which is in line with other studies analyzing surface waters from rivers in Western Europe as well as in China. Statistical analyses show that the plastic concentration close to the mouth of the Danube River was significantly higher than at four nearshore regions along the Romanian and Bulgarian coastline. This could be explained by plastic inputs from the Danube River into the western part of the Black Sea.

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.