Abstract
Microplastics have become ubiquitous in all environments. Yet, their environmental fate is still largely unknown. Plastic fragmentation is a key component of plastic degradation, which is mostly caused by abiotic processes over prolonged time scales. Here, it is shown that the freshwater amphipod Gammarus duebeni can rapidly fragment polyethylene microplastics, resulting in the formation of differently shaped and sized plastic fragments, including nanoplastics. Fragments comprised 65.7% of all observed microplastic particles accumulated in digestive tracts. Higher numbers of fragments were found in response to longer exposure times and/or higher microplastic concentrations. Furthermore, the proportion of smaller plastic fragments was highest when food was present during the depuration process. It is concluded that G. duebeni can rapidly fragment polyethylene microplastics and that this is closely associated with the feeding process. These results highlight the crucial role, currently understudied, that biota may play in determining the fate of microplastics in aquatic ecosystems.
Highlights
Microplastics are small plastic particles of 1 μm to 1 mm in s ize[1] that have been reported to be ubiquitous in marine, freshwater and terrestrial environments[2,3]
The four G. duebeni which died belonged to the following treatment groups: (I) 24 h, low microplastic concentration and depuration in presence of food, (II) 96 h, low microplastic concentration and no depuration, (III) 96 h, low microplastic concentration and depuration in presence of food and (IV) 96 h, high microplastic concentration and no depuration
Microplastic accumulation appeared enhanced when amphipods were exposed to a higher microplastic concentration and a longer exposure time
Summary
Microplastics are small plastic particles of 1 μm to 1 mm in s ize[1] that have been reported to be ubiquitous in marine, freshwater and terrestrial environments[2,3]. It was shown that 10–45 μm polyethylene microplastics are bioavailable to the freshwater amphipod Gammarus duebeni when these plastics are adsorbed to Scientific Reports | (2020) 10:12799. No effect was found on feeding, energy reserves, moulting or mortality after 48 d28 While these studies abundantly show that ingestion of microplastics by invertebrates does occur, the fate of plastics in regard to fragmentation inside organisms after ingestion is still largely unknown. Our preliminary observations in the current study indicated potential accumulation of plastic fragments in G. duebeni digestive tracts after short polyethylene microplastic feeding tests. G. duebeni was selected for microplastic studies as a representative of the amphipods, small crustaceans from the order Amphipoda, that are keystone and model ecotoxicological species[35] which are widespread in marine and freshwater global environments. Our findings of this study show that biological fragmentation of microplastics may have an important role in determining the fate of plastics in the environment worldwide
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