With ever-increasing quantities of plastic being manufactured and ending up in the environment, understanding the consequences of this will be critical to ensure the protection of ecosystems and freshwater resources. This review looks at the sources, abundance, transport, behaviour, fate, associations with chemicals, and ecological consequences of microplastics once they reach freshwater systems. There are many questions which remain to be answered and it is therefore a priority area for future research.
Published October 2017
Research into microplastics within the freshwater environment is rapidly advancing but still lags behind the marine research. There are many questions which remain to be answered surrounding the sources, abundance, transport, behaviour, fate, associations with chemicals and ecological consequences of microplastics once they reach freshwater systems. This is despite the importance of freshwater resources for society, and is, therefore, a priority area for future research.
The evidence available indicates that microplastics are widespread throughout freshwater systems, as is the case with the marine environment. The factors influencing abundance and distribution are complex but, as would be expected, primarily correlate with urbanisation and drainage, both sewage and land-derived. As new information and evidence are constantly emerging, we have not yet managed to develop a comprehensive algorithm to predict where microplastics will travel and accumulate within freshwater environments.
It is clear from both environmental and laboratory studies that organisms will interact with, and ingest, microplastics. The effects of this will vary enormously depending on the size, shape and type of polymer, in addition to the species exposed and the possible combined effects of additional stressors. Different species will interact and be affected by microplastics in different ways due to differing habitat preferences, feeding habits and behaviours. Studies to date suggest that the effects of microplastic ingestion will present as chronic sub-lethal effects with potentially long-term detrimental effects on organisms, leading to population-level effects. However, no studies have yet been carried out to determine the effects of realistic types and concentrations of microplastics on complex ecosystems over chronic, multi-generational timescales. These studies will be necessary to determine real, as opposed to perceived, risk.
Although a concerted effort is underway to develop our understanding of microplastics within freshwater systems, the research would benefit from a collaborative effort to ensure a harmonisation of methods. This would facilitate comparison between studies and extrapolation of data to a variety of organisms and environmental conditions. With ever-increasing quantities of plastic being manufactured and ending up in the environment, understanding the consequences of this will be critical to ensure the protection of ecosystems and freshwater resources.
