BackgroundWhile 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 scienceEnvironmental 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 gapsWhile 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.ConclusionsMP 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.
