Understanding How Microplastics Affect Marine Biota on the Cellular Level Is Important for Assessing Ecosystem Function: A Review

Plastic has become indispensable for human life. When plastic debris is discarded into waterways, these items can interact with organisms. Of particular concern are microscopic plastic particles (microplastics) which are subject to ingestion by several taxa. This review summarizes the results of cutting-edge research about the interactions between a range of aquatic species and microplastics, including effects on biota physiology and secondary ingestion. Uptake pathways via digestive or ventilatory systems are discussed, including (1) the physical penetration of microplastic particles into cellular structures, (2) leaching of chemical additives or adsorbed persistent organic pollutants (POPs), and (3) consequences of bacterial or viral microbiota contamination associated with microplastic ingestion. Following uptake, a number of individual-level effects have been observed, including reduction of feeding activities, reduced growth and reproduction through cellular modifications, and oxidative stress. Microplastic-associated effects on marine biota have become increasingly investigated with growing concerns regarding human health through trophic transfer. We argue that research on the cellular interactions with microplastics provide an understanding of their impact to the organisms’ fitness and, therefore, its ability to sustain their functional role in the ecosystem. The review summarizes information from 236 scientific publications. Of those, only 4.6% extrapolate their research of microplastic intake on individual species to the impact on ecosystem functioning. We emphasize the need for risk evaluation from organismal effects to an ecosystem level to effectively evaluate the effect of microplastic pollution on marine environments. Further studies are encouraged to investigate sublethal effects in the context of environmentally relevant microplastic pollution conditions

Transport of Traffic-Related Microplastic Particles in Receiving Water

A majority of microplastic particles (MPs) in marine waters are transported with rivers from land-based sources. Traffic is estimated to be one of the largest sources of MPs, hence stormwater and subsequently urban waterways are expected to be important transportation routes of MPs to marine waters. However, there is currently little knowledge about MP fate from land sources to marine waters. The aim of this study is to investigate the transport of traffic-related microplastic particles in a receiving freshwater body using hydrodynamic modelling. A model of a 16 km stretch of the G\uf6ta River, Sweden’s largest river, was set up using MIKE 3 FM software. The model builds on data on water flows in the river and its tributaries, water levels and salinity stratification in the Kattegat strait, and meteorological conditions. Concentrations of MPs in stormwater and MP characteristics data, including prevalent particle sizes, density of commonly occurring polymers, and settling velocities were found in the literature. The simulations show that peak concentrations of MPs exhibit a short duration; however, elevated concentrations of MPs may be present for hours after discharge into the river. The simulations indicate that MPs do not settle at the bottom of the river bed; this scenario can be expected for low density MPs including tyre rubber, as well as larger particles (≤ 5 mm) of higher density (> 1 g/cm3). Hence, a high load of MPs from the city of Gothenburg will reach the marine environment. Biofouling and MPs adhering to mineral particles, as has been shown in marine waters, may considerably change the characteristics of MPs and should be considered in future studies