Search

The aim of this study was to explore the adverse effects of a microplastic (MP) mixture obtained from litter accumulated in the Seine River (France) compared to those of their major co-plasticizer, dibutylphthalate (DBP), on the sentinel species Hediste diversicolor. A suite of biomarkers has been investigated to study the impacts of MPs (100 mg kg -1 sediment), DBP (38 μg kg -1 sediment) on worms compared to non-exposed individuals after 4 and 21 days. The antioxidant response, immunity, neurotoxicity and energy and respiratory metabolism were investigated using biomarkers. After 21 days, worms exposed to MPs showed an increasing aerobic metabolism, an enhancement of both antioxidant and neuroimmune responses. Energy-related biomarkers demonstrated that the energy reallocated to the defence system may come from proteins. A similar impact was depicted after DBP exposure, except for neurotoxicity. Our results provide a better understanding of the ecotoxicological effects of environmental MPs and their associated-contaminants on H. diversicolor., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Châtel Amélie reports financial support was provided by Public Interest Group Seine-Aval., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The quantification of macroplastic fluxes transferred by rivers toward the pelagic environment requires a better understanding of macrodebris transfer processes in estuarine environments. Following the strategy adopted in the Seine estuary, this study aims to characterize macroplastic trajectories in the Loire estuary. Between January 2020 and July 2021, 35 trajectories were monitored using plastic bottles equipped with GPS-trackers. With total travelled distances between 100 m and 103.6 km, trajectories show great spatiotemporal variability. The various forcing factors (macroplastic buoyancy, estuaries tidal and hydrometeorological conditions, geomorphology and vegetation) lead to chaotic trajectories, preventing accurate predictions in macroplastic transfer and storage/remobilization dynamics. In the Loire estuary like in the Seine one, no tracked bottle reached the Atlantic Ocean. It confirms that macrotidal estuaries under temperate climates constitute accumulation zones and slow pathways for macroplastics, but raises question on the real fluxes transferred from continental areas to oceans., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Studies on the influence of hydrodynamic conditions on anthropogenic microfiber (MF) and microplastic (MP) distributions in freshwater environments are sparse. In this study, we evaluated the influence of urbanisation gradient on the spatial variability of MFs and MPs. Temporal variability was also assessed by comparing the concentrations and fluxes of MFs and MPs under low flow conditions with those during the January-February 2018 flood event. For each period, Seine river water was collected upstream and downstream of Greater Paris and filtered through an 80 μm net at three different sampling sites. MFs were counted using a stereomicroscope, while MPs were analysed using micro-Fourier transform infrared spectroscopy coupled with siMPle analysis software. The highest concentrations of MFs and MPs were reported at the furthest downstream sites during both periods. However, high water flowrates and urbanisation gradient did not significantly impact MF and MP concentrations, sizes, or polymer distributions. The median MF and MP concentrations were 2.6 and 15.5 items/L and their interquartile ranges were 1.6 and 4.9 items/L (n = 10), respectively, illustrating relatively stable concentrations in spite of the urbanisation gradient and variations in the flowrate. In contrast to the concentration, size, and polymer distribution characteristics, MP mass fluxes were strongly affected by river flow. MF and MP fluxes show increases in the number and mass of particles from upstream to downstream. The downstream site presents high MP mass fluxes, which range between 924 and 1675 tonnes/year. These results may indicate significant MP inputs from the Paris Megacity through wastewater treatment plant effluents and untreated stormwater. The January-February 2018 flood event, which represented 14.5% of the year (in terms of time), contributed 40% of the yearly MP mass fluxes. Thus, flood events contribute strongly to MP fluxes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Macroplastic emissions from the Seine estuary to the English Channel were estimated using institutional cleaning of riverbanks, combined with a tagged litter experiment. Cleaning were performed between March 2018 and April 2019 by the non-profit company Naturaul'un over 19 sites covering 20 km of riverbanks. A total of 365 tagged litter (90% macroplastics) was released in the estuary in March (n = 200), at the end of the winter/spring flood 2018, in July (n = 58), August (n = 56) and September 2018 (n = 51) during low river flow periods. Over the total tagged litter, 102 (28%) were recovered by Naturaul'un. Relative to the total amount of macroplastics (>5 cm) collected and the estimated amount of smaller/hidden macroplastics (>5 mm) not collected, the maximum macroplastic emission to the English Channel was estimated to be ~100-200 metric tons per year., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The dynamics of plastic debris were assessed in the Seine River, especially in the estuary, using plastic bottles equipped with GPS-trackers. In one year, 50 trajectories were recorded, covering a wide range of hydrometeorological conditions. Results show a succession of stranding/remobilization episodes in combination with alternating upstream and downstream transport in the estuary. In the end, 100% of the tracked bottles stranded somewhere, for hours or weeks, from one to several times at different sites. The overall picture shows that different physical phenomena interact with various time scales ranging from hours/days (high/low tides) to weeks/months (spring/neap tides and highest tides) and years (seasonal river flow). Thus, the fate of plastic debris is highly unpredictable, but the consequence of those interactions is that the transfer of debris is chaotic and not straightforward, and its residence time is much longer than the transit time of water., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Rivers are a major pathway for plastics between lands and the ocean. At the land-ocean interface, estuaries make the transfer dynamic of plastics complex and nonlinear. That is why very little is known about this dynamic. In this respect, a specific marker (i.e. Microlax packaging) showing date-prints was systematically investigated in different riverbanks of the Seine estuary to identify the share of "old" and "recent" litter transiting through the estuary toward the ocean. Up to 70% of Microlax were "old" plastic items probably related to the meandering dynamic of the river over large time and space scales, and hydrodynamic conditions (tides) at smaller scales. This contributes together to increase the residence time of plastics into the estuary up to decades with almost endless transport, deposit and remobilization cycles. Consequently, the Seine estuary may function as a "microplastic factory" resulting from the fragmentation of macroplastics into microplastics well before they reach the ocean., Competing Interests: Declaration of competing interest All authors have no competing interests to declare., (Copyright © 2020 Elsevier Ltd. All rights reserved.)