Properties, fate and individual-to-ecosystem level impacts of microplastics in freshwaters
Microplastics that enter lakes and streams could affect the growth and survival of organisms, and have negative effects on biodiversity and key ecosystem processes.
The impacts of microplastics have been studied most extensively in marine ecosystems, but there has been relatively little focus on the behaviour and impacts of microplastics in freshwater ecosystems. The aim of this project it to addresses key gaps in the understanding of the behaviour of different types of microplastics in streams, providing managers and policy makers with a base for effective management, policy and governance strategies for eliminating or reducing the impact of microplastics in freshwater ecosystems.
State-of-the-art facilities in Norway and Germany will be used to run whole channel experiments, whereas the world-leading Phytotron controlled environment facility at SLU Uppsala will be used for microcosm experiments.
The aim of the project is to:
- quantify how the properties (e.g. size, shape, sorption and biofouling potential) of different types of microplastics regulate their fate and impacts in stream ecosystems;
- evaluate the risks associated with microplastics relative to natural organic particles;
- identify the potentially most harmful types of microplastics in riverine networks as an aid in hazard evaluation.
More specifically, the following research questions will be addressed:
- What are the properties of microplastics originating from different parent materials, how do they compare with the properties of naturally occurring particulate organic matter and how are these properties modified through exposure in aquatic habitats (microbial biofilms, gut passage, biofouling, photo weathering etc.)?
- Which microplastic properties influence their physical fate in streams (sedimentation, dispersion, aggregation) and their uptake by biota with different feeding strategies?
- How do microplastics impact the growth and survival of individual consumers and do they alter biodiversity and community composition, and ecosystem functioning?
- Are microplastics transferred from primary to secondary consumers in stream food webs?
- What is the capacity of microplastics to adsorb chemical stressors relative to naturally occurring particulate organic matter? What is the hazard associated with this process?
- How do microplastics interact with chemical stressors in impacting growth and survival of individuals, community composition, and ecosystem functioning?
- How do we rank the potential risk posed by different types of microplastics to the environment and human food chain, to contribute to responsible management and governance of plastics?
Concern about the environmental impacts of microplastics and their implications for human health and wellbeing has never been higher. Unfortunately, growth in the empirical understanding of the dynamics and ecological and health impacts of microplastics lags behind. This hinders the capacity of scientists, managers and policy makers to address public concerns about the true level of risk posed by MPs (e.g. to the environment and to the human food chain), and to develop effective management, policy and governance strategies for eliminating or reducing those risks. Such action is urgently needed for the protection of aquatic ecosystems in particular, where microplastics accumulation is worryingly high (Claessens, et al. 2013; Free, et al. 2014).
Vast quantities of plastic waste enter aquatic ecosystems primarily via terrestrial runoff (e.g. storm water from urban and industrial areas where plastic use is high), wastewater or windthrow. Some of this plastic waste, known as “primary microplastics”, is already in microplastic form (particle ø ≤ 5 mm), premanufactured as beads, fibres or other shapes. Additionally, larger plastic waste particles can be reduced down to microparticle size, due to physicochemical- (including photo- and mechanical degradation) and biodegradation processes, and is then known as “secondary microplastics”.
The impacts of microplastics have been studied most extensively in marine ecosystems, focussing especially on fish, reflecting the importance of marine fisheries in human food supply. Documented impacts include interruption of dietary processes, growth and metabolism (e.g. increased energy expenditure, reduced growth) and altered neurological and genetic function. Microplastics also interact with other stressors, particularly chemical stressors (e.g. by binding toxins, which may increase toxin transport and uptake into the food web) and can increase biofouling (by acting as substrates for excessive biofilm development, and forming aggregates with algal or bacterial cells).
In contrast, there has been relatively little focus on the behaviour and impacts of microplastics in freshwater ecosystems. This is despite the vulnerability of freshwaters to inputs of plastic waste, especially via storm water and other terrestrial runoff, and the potential of stream and river networks to act as key transport pathways through the landscape. Indeed, the importance of running waters for the transport, transformation, and biological uptake of naturally occurring particulate organic matter (i.e. particles with a high organic carbon content arising especially from organic detritus), is well established. It is likely that stream and river networks play a similar key role in regulating the fate of microplastics in the environment, including uptake into the human food chain.
Brendan G. McKie (SLU)
Martyn N. Futter (SLU)
Micro Bundschuh (SLU)
Dr. Rachel Hurley (Norwegian Institute for Water Research, NIVA)