Microplastics found in the stomach contents of Squalius cephalus from the Seine River

Microplastics (plastics < 5 mm) are emerging pollutants of growing concern. Since the 2000s their abundance, degradation and impacts on wildlife are more and more studied and understood. However, few data are available particularly in freshwater ecosystems. Some fish species have plastic in their stomach contents such as: Gobio gobio, Alburnus alburnus, Leuciscus leuciscus while other species have not. In controlled conditions, microplastics were found to cause negative impacts in fish: leaching of micropollutants, endocrine disruption, hatching inhibition and decrease of growth rate of larvae. The first step in the understanding of these impacts is the quantification and the characterisation of ingested plastics by organisms in the field. Plastics and other anthropogenic particles (textile fibres) were isolated from 40 stomachs of Squalius cephalus (the European chub) collected in the Seine River (Paris) in August 2016. One station is upstream and the three others are downstream of the Paris Megacity conurbation. This megacity exerts a great pressure on the Seine River. Plastics were isolated thanks to a method using sodium hypochlorite and all particles were then analysed by Raman spectroscopy. The method consists in a degradation overnight of the organic matter in the stomach contents by sodium hypochlorite. This mixture is then filtrated and particles longer than 5 µm are resuspended into an ethanol (99%) solution for centrifugation. The precipitate, containing all particles denser than ethanol, is collected (1.3 ml) and spread on a mount for Raman spectroscopy. Several lasers were used, depending on the particle’s colour. Spectra were recorded with an accumulation ranging from 5 to 50s. Preliminary results showed that 7 individuals out of 25 already analysed (28%) had ingested at least one anthropogenic particle (AP). Eight APs were found and characterized, the majority of them (7) being dyed fibres. One of these fibres was made of a plastic polymer, the polyethylene terephthalate. The others were made of an undetermined material as Raman analyses gave only information on the dye. The eighth particle was a fragment of polypropylene. It is the first time that fish are studied as a part of plastic pollution in the Seine River. All isolated particles have been analysed leading to precise results. The percentage of occurrence is in the common range of other studies while much lower than the European flounder coming from the River Thames and higher than fish coming from Geneva Lake. It is not surprising that the majority of APs were fibres as another study in the river Seine found that the fibres concentration in water is far greater than the fragments concentration, as well as in urban runoff. It is also possible that the retention time of fibres in the gut is longer than fragments. Toxicological impacts of fibre ingestion is still unknown despite their ubiquity in many freshwater environments.