Posted on

Microplastics in freshwater ecosystems: what we know and what we need to know

Author: Martin Wagner, Christian Scherer, Diana Alvarez-Muñoz, Nicole Brennholt, Xavier Bourrain, Sebastian Buchinger, Elke Fries, Cécile Grosbois, Jörg Klasmeier, Teresa Marti, Sara Rodriguez-Mozaz, Ralph Urbatzka, A. Dick Vethaak, Margrethe Winther-Nielsen & Georg Reifferscheid
Year of Publication: 2014
Published:

Abstract:
Background
While the use of plastic materials has generated huge societal benefits, the ‘plastic age’ comes with downsides: One issue of emerging concern is the accumulation of plastics in the aquatic environment. Here, so-called microplastics (MP), fragments smaller than 5 mm, are of special concern because they can be ingested throughout the food web more readily than larger particles. Focusing on freshwater MP, we briefly review the state of the science to identify gaps of knowledge and deduce research needs.

State of the science
Environmental scientists started investigating marine (micro)plastics in the early 2000s. Today, a wealth of studies demonstrates that MP have ubiquitously permeated the marine ecosystem, including the polar regions and the deep sea. MP ingestion has been documented for an increasing number of marine species. However, to date, only few studies investigate their biological effects.

The majority of marine plastics are considered to originate from land-based sources, including surface waters. Although they may be important transport pathways of MP, data from freshwater ecosystems is scarce. So far, only few studies provide evidence for the presence of MP in rivers and lakes. Data on MP uptake by freshwater invertebrates and fish is very limited.

Knowledge gaps
While the research on marine MP is more advanced, there are immense gaps of knowledge regarding freshwater MP. Data on their abundance is fragmentary for large and absent for small surface waters. Likewise, relevant sources and the environmental fate remain to be investigated. Data on the biological effects of MP in freshwater species is completely lacking. The accumulation of other freshwater contaminants on MP is of special interest because ingestion might increase the chemical exposure. Again, data is unavailable on this important issue.

Conclusions
MP represent freshwater contaminants of emerging concern. However, to assess the environmental risk associated with MP, comprehensive data on their abundance, fate, sources, and biological effects in freshwater ecosystems are needed. Establishing such data critically depends on a collaborative effort by environmental scientists from diverse disciplines (chemistry, hydrology, ecotoxicology, etc.) and, unsurprisingly, on the allocation of sufficient public funding.

Keywords:
Chemistry, Ecotoxicology, Environmental  quality, Litter, Microplastics, Monitoring, Plastics, Polymers, Review, Water framework directive

Citation:
Martin Wagner, Christian Scherer, Diana Alvarez-Muñoz, Nicole Brennholt, Xavier Bourrain, Sebastian Buchinger, Elke Fries, Cécile Grosbois, Jörg Klasmeier, Teresa Marti, Sara Rodriguez-Mozaz, Ralph Urbatzka, A. Dick Vethaak, Margrethe Winther-Nielsen & Georg Reifferscheid (2014): Microplastics in freshwater ecosystems: what we know and what we need to know. Environmental Sciences Europe 26:12.

http://www.enveurope.com/content/26/1/12/abstract

Posted on

Freshwater microplastics: challenges for regulation and management. In: Martin Wagner & Scott Lambert (Eds.): Freshwater microplastics: Emerging environmental contaminants?

Author: Nicole Brennholt, Maren Heß & Georg Reifferscheid
Year of Publication: 2017
Published: Martin Wagner & Scott Lambert (Eds.): Freshwater microplastics: Emerging environmental contaminants? The Handbook of Environmental Chemistry. Springer-Verlag

Abstract:
The accumulation of plastic debris in aquatic environments is one of the major but least studied human pressures on aquatic ecosystems. Besides the general waste burden in waterbodies, (micro)plastic debris gives rise to ecological and social problems. Related to marine ecosystems, these problems are already in the center of interest of science, policy, and public. The United Nations Environment Programme, for instance, drafted a joint report on “marine plastic debris and microplastics,” and the European Community included the issue into the European Marine Strategy Framework Directive, descriptor 10 “marine litter.”

However, (micro)plastic litter in freshwater systems is not yet explicitly addressed in the respective regulations, although the issue is relevant for many international and national policy instruments and initiatives. Many conventions, agreements, regulations, strategies, action plans, programs, and guidelines refer to “all wastes” in general. This should also concern (micro)plastic waste.

This chapter provides an overview of the regulatory instruments developed at different levels to address freshwater (micro)plastic litter. Beyond that, specific management options and measures that are either compulsory or voluntary are presented. Nevertheless, only few options have been realized so far. Reasons are numerous, first and foremost the lack of consensus on the definition of microplastics.

The complexity of these particulate stressors with very heterogeneous physicochemical characteristics poses new challenges for regulation and management. We highlight the most important questions from the perspective of freshwater monitoring. Furthermore, we discuss a possible adaption of existing environmental policy instruments and potential management options for single categories of (micro)plastics.

Keywords:
Environmental plastics, Microplastics, National–international policy instruments, Science–policy interface

Citation:
Nicole Brennholt, Maren Heß & Georg Reifferscheid (2017): Freshwater microplastics: challenges for regulation and management. In: Martin Wagner & Scott Lambert (Eds.): Freshwater microplastics: Emerging environmental contaminants? The Handbook of Environmental Chemistry. Springer-Verlag.

https://www.springer.com/de/book/9783319616148

Posted on

Interactions of microplastics with freshwater biota. In: Martin Wagner & Scott Lambert (Eds.): Freshwater microplastics: Emerging environmental contaminants?

Author: Christian Scherer, Annkatrin Weber, Scott Lambert, Martin Wagner
Year of Publication: 2017
Published: Martin Wagner & Scott Lambert (Eds.): Freshwater microplastics: Emerging environmental contaminants? The Handbook of Environmental Chemistry. Springer-Verlag.

Abstract:
The ubiquitous detection of microplastics in aquatic ecosystems promotes the concern for adverse impacts on freshwater ecosystems. The wide variety of material types, sizes, shapes, and physicochemical properties renders interactions with biota via multiple pathways probable.

So far, our knowledge about the uptake and biological effects of microplastics comes from laboratory studies, applying simplified exposure regimes (e.g., one polymer and size, spherical shape, high concentrations) often with limited environmental relevance. However, the available data illustrates species- and material-related interactions and highlights that microplastics represent a multifaceted stressor. Particle-related toxicities will be driven by polymer type, size, and shape. Chemical toxicity is driven by the adsorption-desorption kinetics of additives and pollutants. In addition, microbial colonization, the formation of hetero-aggregates, and the evolutionary adaptations of the biological receptor further increase the complexity of microplastics as stressors. Therefore, the aim of this chapter is to synthesize and critically revisit these aspects based on the state of the science in freshwater research. Where unavailable we supplement this with data on marine biota. This provides an insight into the direction of future research.

In this regard, the challenge is to understand the complex interactions of biota and plastic materials and to identify the toxicologically most relevant characteristics of the plethora of microplastics. Importantly, as the direct biological impacts of natural particles may be similar, future research needs to benchmark synthetic against natural materials. Finally, given the scale of the research question, we need a multidisciplinary approach to understand the role of microplastics in a multiple-particle world.

Keywords:
Autecology, Feeding types, Microplastic-biota interaction, Polymers, Suspended solids, Vector 

Citation:
Christian Scherer, Annkatrin Weber, Scott Lambert, Martin Wagner (2017): Interactions of microplastics with freshwater biota. In: Martin Wagner & Scott Lambert (Eds.): Freshwater microplastics: Emerging environmental contaminants? The Handbook of Environmental Chemistry. Springer-Verlag.

https://www.springer.com/de/book/9783319616148

Posted on

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

Posted on

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

Posted on

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