Particle shape does not affect ingestion and egestion of microplastics by the freshwater shrimp Neocaridina palmata

Abstract

The ingestion of microplastics (MPs) is well documented for various animals and spherical MPs (beads) in many studies. However, the retention time and egestion of MPs have been examined less, especially for irregular MPs (fragments) which are predominantly found in the environment. Furthermore, the accumulation of such particles in the gastrointestinal tract is likely to determine whether adverse effects are induced. To address this, we investigated if the ingestion and egestion of beads are different to those of fragments in the freshwater shrimp Neocaridina palmata. Therefore, organisms were exposed to 20–20,000 particles L−1 of either polyethylene (PE) beads (41 μm and 87 μm) or polyvinyl chloride (PVC) fragments (<63 μm). Moreover, shrimps were exposed to 20,000 particles L−1 of either 41 μm PE and 11 μm polystyrene (PS) beads or the PVC fragments for 24 h, followed by a post-exposure period of 4 h to analyze the excretion of particles. To simulate natural conditions, an additional fragment ingestion study was performed in the presence of food. After each treatment, the shrimps were analyzed for retained or excreted particles. Our results demonstrate that the ingestion of beads and fragments were concentration-dependent. Shrimps egested 59% of beads and 18% of fragments within 4 h. Particle shape did not significantly affect MP ingestion or egestion, but size was a relevant factor. Medium- and small-sized beads were frequently ingested. Furthermore, fragment uptake decreased slightly when co-exposed to food, but was not significantly different to the treatments without food. Finally, the investigations highlight that the assessment of ingestion and egestion rates can help to clarify whether MPs remain in specific organisms and, thereby, become a potential health threat.

Locomotor behavior of Neocaridina palmata: a study with leachates from UV-weathered microplastics

“…The materials were selected because recycled and biodegradable plastics are increasingly used as alternative materials for conventional plastics ( De Schoenmakere et al, 2019 ; Shen et al, 2020 ) and because of their known high in vitro toxicities (comp. Table S3 , Klein et al, 2021a ). The foil was cut into 1 × 1 cm pieces with stainless steel scissors.…”

“…Each MP (100 g) was weathered with UV-A/B irradiation (280–400 nm) for 24 h in a climate chamber (ThermoTEC 1501; ThermoTEC Weilburg GmbH & Co. KG, Weilburg, Germany), similarly to the procedure in Klein et al (2021a) for plastic pellets where the irradiation time and intensity led to accelerated weathering of the plastics in terms of the enhancement of chemical leaching. The present study, however, includes MPs with a comparably higher surface area due to the milling process.…”

“…The MP leachates and the procedural blank were acidified to pH 2.5 (3.5 mol H 2 SO 4 L −1 ) and enriched via solid-phase extraction (SPE) using the Telos C18/ENV cartridges (Kinesis GmbH, Wertheim, Germany). The elution and enrichment were performed as described in Klein et al (2021a) . Afterwards, the duplicates of the respective MP extracts (2 × 200 µL) were combined and resulted in 400 µL extracts with dimethyl sulfoxide (DMSO) as solvent.…”

“…The final solvent concentration did not exceed 1% (v/v) per well. The effects of the MP extracts were compared to the findings of the previously published study Klein et al (2021a) . Moreover, the in vitro response of the MP extracts was compared to that of the positive control in order to evaluate the environmental relevance.…”

“…For the materials, we selected post-industrial recycled low-density polyethylene (LDPE-R) pellets and a biodegradable, partly bio-based starch blend (SB) foil that we previously identified to induce high in vitro toxicities including baseline toxicity, oxidative stress and endocrine activities ( Klein et al, 2021a and K. Klein et al, 2020, unpublished data). Comparable to Klein et al (2021a) , we further weathered the MPs with artificial UV-A/B light and leached them afterwards in ultrapure water, taking into consideration the formed degradation products. Finally, we conducted the Microtox assay in order to assess the baseline toxicity of the leachable chemicals from the unweathered and UV-weathered MP samples.…”