title: Influence of environmental and anthropogenic factors on the composition, concentration and spatial distribution of microplastics: A case study of the Bay of Brest (Brittany, France).
abstract: The concentration and spatial distribution of microplastics in the Bay of Brest (Brittany, France) was investigated in two surveys. Surface water and sediment were sampled at nine locations in areas characterized by contrasting anthropic pressures, riverine influences or water mixing. Microplastics were categorized by their polymer type and size class. Microplastic contamination in surface water and sediment was dominated by polyethylene fragments (PE, 53-67%) followed by polypropylene (PP, 16-30%) and polystyrene (PS, 16-17%) microparticles. The presence of buoyant microplastics (PE, PP and PS) in sediment suggests the existence of physical and/or biological processes leading to vertical transfer of lightweight microplastics in the bay. In sediment (upper 5 cm), the percentage of particles identified by Raman micro-spectroscopy was lower (41%) than in surface water (79%) and may explain the apparent low concentration observed in this matrix (0.97 ± 2.08 MP kg-1dry sediment). Mean microplastic concentration was 0.24 ± 0.35 MP m-3in surface water. We suggest that the observed spatial MP distribution is related to proximity to urbanized areas and to hydrodynamics in the bay. A particle dispersal model was used to study the influence of hydrodynamics on surface microplastic distribution. The outputs of the model showed the presence of a transitional convergence zone in the centre of the bay during flood tide, where floating debris coming from the northern and southern parts of the bay tends to accumulate before being expelled from the bay. Further modelling work and observations integrating (i) the complex vertical motion of microplastics, and (ii) their point sources is required to better understand the fate of microplastics in such a complex coastal ecosystem.
authors.affiliation: LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, IUEM, rue Dumont d'Urville, 29280 Plouzané, France.
authors.forename: L
authors.initials: L
authors.lastname: Frère
authors.affiliation: LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, IUEM, rue Dumont d'Urville, 29280 Plouzané, France. Electronic address: ika.paulpont@univ-brest.fr.
authors.forename: I
authors.initials: I
authors.lastname: Paul-Pont
authors.affiliation: Ifremer, Laboratoire Détection, Capteurs et Mesures, Centre de Bretagne, ZI de la Pointe du Diable, CS 10070, 29280 Plouzané, France.
authors.forename: E
authors.initials: E
authors.lastname: Rinnert
authors.affiliation: Ifremer, LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, Centre de Bretagne, ZI de la Pointe du Diable, CS 10070, 29280 Plouzané, France.
authors.forename: S
authors.initials: S
authors.lastname: Petton
authors.affiliation: LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, IUEM, rue Dumont d'Urville, 29280 Plouzané, France.
authors.forename: J
authors.initials: J
authors.lastname: Jaffré
authors.affiliation: LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, IUEM, rue Dumont d'Urville, 29280 Plouzané, France.
authors.forename: I
authors.initials: I
authors.lastname: Bihannic
authors.affiliation: LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, IUEM, rue Dumont d'Urville, 29280 Plouzané, France.
authors.forename: P
authors.initials: P
authors.lastname: Soudant
authors.affiliation: LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, IUEM, rue Dumont d'Urville, 29280 Plouzané, France.
authors.forename: C
authors.initials: C
authors.lastname: Lambert
authors.affiliation: Ifremer, LEMAR UMR 6539 CNRS/UBO/IRD/Ifremer, Centre de Bretagne, ZI de la Pointe du Diable, CS 10070, 29280 Plouzané, France.
authors.forename: A
authors.initials: A
authors.lastname: Huvet
mesh_terms: D061006:Bays / Q000737:chemistry*; D004777:Environment; D004784:Environmental Monitoring; D005602:France; D010969:Plastics / Q000032:analysis* / Q000737:chemistry; D020959:Polyethylene / Q000032:analysis; D011108:Polymers / Q000032:analysis; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000706:statistics & numerical data
chemical_list: D010969:Plastics; D011108:Polymers; D014874:Water Pollutants, Chemical; D020959:Polyethylene
keywords: Coastal ecosystem; Dispersal particle modelling; Hydrodynamic; Microplastic; Raman spectroscopy; Sediment; Surface water