Do weathered microplastics impact the planktonic community? A mesocosm approach in the Baltic Sea

Linea Gry Ebbesen; Markus Varlund Strange; Kuddithamby Gunaalan; Maria Lund Paulsen; Alicia Herrera; Torkel Gissel Nielsen; Yvonne Shashoua; Martin Lindegren; Rodrigo Almeda

doi:10.1016/j.watres.2024.121500

Do weathered microplastics impact the planktonic community? A mesocosm approach in the Baltic Sea

Water Res. 2024 May 15:255:121500. doi: 10.1016/j.watres.2024.121500. Epub 2024 Mar 21.

Authors

Linea Gry Ebbesen¹, Markus Varlund Strange¹, Kuddithamby Gunaalan², Maria Lund Paulsen³, Alicia Herrera⁴, Torkel Gissel Nielsen², Yvonne Shashoua⁵, Martin Lindegren², Rodrigo Almeda⁶

Affiliations

¹ Department of Environmental Engineering, Technical University of Denmark, Denmark; National Institute of Aquatic Resources (DTU AQUA) Technical University of Denmark, Denmark.
² National Institute of Aquatic Resources (DTU AQUA) Technical University of Denmark, Denmark.
³ Department of Biology, Aquatic Biology, Aarhus University, Denmark.
⁴ EOMAR, ECOAQUA, University of Las Palmas de Gran Canaria, Spain.
⁵ Environmental Archaeology and Materials Science, National Museum of Denmark, Denmark.
⁶ National Institute of Aquatic Resources (DTU AQUA) Technical University of Denmark, Denmark; EOMAR, ECOAQUA, University of Las Palmas de Gran Canaria, Spain. Electronic address: rodrigo.almeda@ulpgc.es.

PMID: 38554636
DOI: 10.1016/j.watres.2024.121500

Abstract

Microplastics (MPs) are ubiquitous pollutants of increasing concern in aquatic systems. However, little is still known about the impacts of weathered MPs on plankton at the community level after long-term exposure. In this study, we investigated the effects of weathered MPs on the structure and dynamics of a Baltic Sea planktonic community during ca. 5 weeks of exposure using a mesocosm approach (2 m³) mimicking natural conditions. MPs were obtained from micronized commercial materials of polyvinyl chloride, polypropylene, polystyrene, and polyamide (nylon) previously weathered by thermal ageing and sunlight exposure. The planktonic community was exposed to 2 μg L^-1 and 2 mg L^-1 of MPs corresponding to measured particle concentrations (10-120 μm) of 680 MPs L^-1 and 680 MPs mL^-1, respectively. The abundance and composition of all size classes and groups of plankton and chlorophyll concentrations were periodically analyzed throughout the experiment. The population dynamics of the studied groups showed some variations between treatments, with negative and positive effects of MPs exhibited depending on the group and exposure time. The abundance of heterotrophic bacteria, pico- and nanophytoplankton, cryptophytes, and ciliates was lower in the treatment with the higher MP concentration than in the control at the last weeks of the exposure. The chlorophyll concentration and the abundances of heterotrophic nanoflagellates, Astromoeba, dinoflagellate, diatom, and metazooplankton were not negatively affected by the exposure to MPs and, in some cases, some groups showed even higher abundances in the MP treatments. Despite these tendencies, statistical analyses indicate that in most cases there were no statistically significant differences between treatments over the exposure period, even at very high exposure concentrations. Our results show that weathered MPs of the studied conventional plastic materials have minimal or negligible impact on planktonic communities after long-term exposure to environmentally relevant concentrations.

Keywords: Baltic Sea; Long-term exposure; Mesocosms; Microplastics; Plankton; Weathering.