title: Microplastic interactions with freshwater microalgae: Hetero-aggregation and changes in plastic density appear strongly dependent on polymer type.
abstract: In this study, the interactions between microplastics, chosen among the most widely used in industry such as polypropylene (PP) and high-density polyethylene (HDPE), and a model freshwater microalgae, Chlamydomas reinhardtii, were investigated. It was shown that the presence of high concentrations of microplastics with size >400 μm did not directly impact the growth of microalgae in the first days of contact and that the expression of three genes involved in the stress response was not modified after 78 days. In parallel, a similar colonization was observed for the two polymers. However, after 20 days of contact, in the case of PP only, hetero-aggregates constituted of microalgae, microplastics and exopolysaccharides were formed. An estimation of the hetero-aggregates composition was approximately 50% of PP fragments and 50% of microalgae, which led to a final density close to 1.2. Such hetero-aggregates appear as an important pathway for the vertical transport of PP microplastics from the water surface to sediment. Moreover, after more than 70 days of contact with microplastics, the microalgae genes involved in the sugar biosynthesis pathways were strongly over-expressed compared to control conditions. The levels of over-expression were higher in the case of HDPE than in PP condition. This work presents the first evidence that depending on their chemical nature, microplastics will follow different fates in the environment.
authors.affiliation: Institut des Molécules et des Matériaux du Mans, UMR CNRS 6283, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France. Electronic address: fabienne.lagarde@univ-lemans.fr.
authors.forename: Fabienne
authors.initials: F
authors.lastname: Lagarde
authors.affiliation: Institut des Molécules et des Matériaux du Mans, UMR CNRS 6283, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France; Laboratoire Mer, Molécules, Santé (EA 2160), Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France.
authors.forename: Ophélie
authors.initials: O
authors.lastname: Olivier
authors.affiliation: Laboratoire Mer, Molécules, Santé (EA 2160), Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Zanella
authors.affiliation: Institut des Molécules et des Matériaux du Mans, UMR CNRS 6283, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Daniel
authors.affiliation: Laboratoire Mer, Molécules, Santé (EA 2160), Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Hiard
authors.affiliation: Laboratoire Mer, Molécules, Santé (EA 2160), Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans Cedex, France.
authors.forename: Aurore
authors.initials: A
authors.lastname: Caruso
mesh_terms: D004784:Environmental Monitoring; D005618:Fresh Water / Q000737:chemistry*; D015870:Gene Expression; D019015:Geologic Sediments; D058086:Microalgae / Q000235:genetics / Q000254:growth & development*; D010316:Particle Size; D010969:Plastics / Q000737:chemistry; D020959:Polyethylene / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D011126:Polypropylenes / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014876:Water Pollution
chemical_list: D010969:Plastics; D011108:Polymers; D011126:Polypropylenes; D011134:Polysaccharides; D014874:Water Pollutants, Chemical; D014867:Water; D020959:Polyethylene
keywords: Hetero-aggregates; Microalgae; Microplastics; Plastic pollution; Polyethylene; Polypropylene