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Feeding strategy and development drive the ingestion of microplastics by freshwater invertebrates

Author: Christian Scherer, Nicole Brennholt, Georg Reifferscheid & Martin Wagner
Year of Publication: 2017
Published: Scientific Reports Volume 7

Abstract:
Microscopic plastic items (microplastics) are ubiquitously present in aquatic ecosystems. With decreasing size their availability and potential to accumulate throughout food webs increase. However, little is known on the uptake of microplastics by freshwater invertebrates. To address this, we exposed species with different feeding strategies to 1, 10 and 90 µm fluorescent polystyrene spheres (3–3 000 particles mL−1). Additionally, we investigated how developmental stages and a co-exposure to natural particles (e.g., food) modulate microplastic ingestion. All species ingested microplastics in a concentration-dependent manner with Daphnia magna consuming up to 6 180 particles h−1, followed by Chironomus riparius (226 particles h−1), Physella acuta (118 particles h−1), Gammarus pulex (10 particles h−1) and Lumbriculus variegatus (8 particles h−1). D. magna did not ingest 90 µm microplastics whereas the other species preferred larger microplastics over 1 µm in size. In C. riparius and D. magna, size preference depended on the life stage with larger specimens ingesting more and larger microplastics. The presence of natural particles generally reduced the microplastics uptake. Our results demonstrate that freshwater invertebrates have the capacity to ingest microplastics. However, the quantity of uptake depends on their feeding type and morphology as well as on the availability of microplastics.

Keywords:
Microplastics, uptake, freshwater invertebrates, polystyrene spheres

Citation:
Christian Scherer, Nicole Brennholt, Georg Reifferscheid & Martin Wagner (2017): Feeding strategy and development drive the ingestion of microplastics by freshwater invertebrates. Scientific Reports Volume 7.

http://www.nature.com/articles/s41598-017-17191-7

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A new approach in separating microplastics from environmental samples based on their electrostatic behavior

Author: Stefanie Felsing, Christian Kochleus, Sebastian Buchinger, Nicole Brennholt, Friederike Stock, Georg Reifferscheid
Year of Publication: 2018
Published: Environmental Pollution Volume 234: 20-28

Abstract:
Numerous studies on microplastics (MPs; Ø < 5 mm) in the aquatic environment have been published, but knowledge about the occurrence and ecological risks of MPs is limited. This is in part because current data on the distribution of MPs are comparable only to a limited extent, due to the many different methods of investigation. In addition, sample preparation is often difficult such that standard procedures are lacking. The aim of this work was to simplify the preparation of different kinds of MP samples. Our method makes use of the electrostatic behavior of plastic particles to facilitate their separation from sample matter, with up to 99% of the original sample mass removed without any loss of MPs. To determine the efficacy of this approach, four different materials (quartz sand, freshwater suspended particulate matter, freshwater sediment, and beach sand) were spiked with MPs (size: 0.063–5 mm from the seven most common types of plastics, one bioplastic type, polyethylene fibers, and tire wear. A modified electrostatic metal/plastic separator was used to reduce the sample mass and concentrate the plastics based on their physical separation. The recovery achieved with this method was as high as nearly 100% for each type of material. The method was then tested on plastic particles of different shapes and types isolated from the Rhine River. These were successfully electroseparated from the four materials, which demonstrated the utility of this method. Its advantages include the simplified handling and preparation of different field samples as well as a much shorter processing time, because after the last separation step there is hardly any biological material remaining in the sample fraction.

Keywords:
Tire wear, Freshwater suspended particulate matter, Beach sand, Electroseparation, Physical separation, Sediment

Citation:
Stefanie Felsing, Christian Kochleus, Sebastian Buchinger, Nicole Brennholt, Friederike Stock, Georg Reifferscheid (2018): A new approach in separating microplastics from environmental samples based on their electrostatic behavior. Environmental Pollution Volume 234: 20-28

https://www.sciencedirect.com/science/article/pii/S0269749117316548

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PET microplastics do not negatively affect the survival, development, metabolism and feeding activity of the freshwater invertebrate Gammarus pulex

Author: Annkatrin Weber, Christian Scherer, Nicole Brennholt, Georg Reifferscheid, Martin Wagner
Year of Publication: 2018
Published: Environmental Pollution 234: 181-189

Abstract:
Over the past decade, microscopic plastic debris, known as microplastics, emerged as a contaminant of concern in marine and freshwater ecosystems. Although regularly detected in aquatic environments, the toxicity of those synthetic particles is not well understood. To address this, we investigated whether the exposure to microplastics adversely affects the amphipod Gammarus pulex, a key freshwater invertebrate.

Juvenile (6–9 mm) and adult (12–17 mm) individuals were exposed to irregular, fluorescent polyethylene terephthalate fragments (PET, 10–150 μm; 0.8–4,000 particles mL−1) for 24 h. Results show that body burden after 24 h depends on the dose and age of G. pulex with juveniles ingesting more microplastics than adults. After chronic exposure over 48 d, microplastics did not significantly affect survival, development (molting), metabolism (glycogen, lipid storage) and feeding activity of G. pulex.

This demonstrates that even high concentrations of PET particles did not negatively interfere with the analyzed endpoints. These results contradict previous research on marine crustaceans. Differences may result from variations in the exposure regimes (e.g., duration, particle concentrations), plastic characteristics (e.g., type, size, shape, additives) as well as the species-specific morphological, physiological and behavioral traits. As a detritivorous shredder G. pulex is adapted to feed on non-digestible materials and might, therefore, be less sensitive towards exposure to synthetic particles. Accordingly, we argue that the autecology needs to be taken into account and that research should focus on identifying traits that render species susceptible to microplastic exposure.

Keywords:
Amphipods, Body burden, Ecotoxicology, Effects, Polymers, Toxicity

Citation:
Annkatrin Weber, Christian Scherer, Nicole Brennholt, Georg Reifferscheid, Martin Wagner (2018): PET microplastics do not negatively affect the survival, development, metabolism and feeding activity of the freshwater invertebrate Gammarus pulex. Environmental Pollution 234: 181-189

https://doi.org/10.1016/j.envpol.2017.11.014