Effects of biodegradable microplastics on freshwater and terrestrial organisms

Plastic pollution has become a worldwide problem, as large amount of plastic waste ends up in landfills or in the natural environment. A particular problem is the fragmentation of plastic into microplastics. Numerous adverse effects of microplastics on the environment, including freshwater and terrestrial organisms, have been demonstrated. Substitution of conventional plastics with biodegradable plastics is generally considered a sustainable alternative to reduce the accumulation of plastic waste in the environment. However, various authorities and the scientific community have raised concerns about actual biodegradability in the environment. This is because materials labelled ""biodegradable"" degrade under specific conditions (e.g. in industrial composter) and do not necessarily degrade under natural conditions. In addition, large amounts of microplastics are produced during the degradation process, perhaps even more than conventional plastics over the same period of time. Currently, there is limited information on the environmental hazards of microplastics from biodegradable materials (biodegradable microplastics), particularly to terrestrial organisms and some freshwater species. The ""MicroBIOplast"" project aims to study the effects of biodegradable microplastics on a range of freshwater and terrestrial organisms. The selection of plastics will include various biobased and fossil-based biodegradable materials, including non-biodegradable reference materials for comparison. The project will run within 4 research work packages: WP1-Microplastics and characterization, WP2- Biodegradability testing, WP3- Effects on freshwater organisms, and WP4- Effects on terrestrial organisms. In the first phase, the biodegradability of plastics will be tested under simulated environmental conditions in various freshwaters and soils (WP2). After biodegradation, the microplastics will be extracted from the water and used in ecotoxicity tests with freshwater organisms (WP3). In the case of soil, the soils that contain microplastics will be directly tested (WP4). For comparison, microplastics will be also cryo-milled from selected plastics to simulate mechanical formation of microplastics. Physicochemical properties, additive content and leaching will be determined for all types of microplastics (WP1). The core of the project will be the investigation of effects on organisms. A number of commonly used freshwater and terrestrial organisms representing different trophic positions (primary producers and consumers) and taxonomic positions (protozoa, invertebrates, plants) will be included. These are the crustacean water flea Daphnia magna, the protozoan Tetrahymena thermophila, the aquatic plant duckweed Lemna minor, terrestrial crustacean woodlice Porcelio scaber, the mealworm Tenebrio molitor, and terrestrial plants commonly grown as crops, such as the sunflower Helianthus annuus and the corn Zea mays. Different endpoints will be studied covering different physiological processes in the organisms: microplastic ingestion, cell viability, swimming behaviour, body surface interaction/adhesion, immune response, development and metamorphosis, energy-related physiological changes, plant growth, development and biochemical response, and mortality.  The ""MicroBIOplast"" will provide new knowledge about the biodegradation of plastics in the natural environment, the production of microplastics during biodegradation, and a holistic understanding of the responses of organisms to exposure to microplastics at different levels of biological complexity. This knowledge will help us identify the harmful effects of microplastics and understand the importance of plastic biodegradation to microplastic toxicity. The results of this project will therefore have a major impact on research on the environmental safety of biodegradable microplastics and will be of great environmental and social importance.