Impact of environmentally relevant nano- and micro-plastics on soil invertebrates

In recent years, nano- and micro-plastics pollution (NMPs) has become one of the major public environmental concerns expressed throughout the globe. Although terrestrial environment is a substantial source and sink of NMPs pollution, there is still a lack of comparative knowledge regarding potential sublethal effects that nano- and micro-plastics may have on terrestrial organisms. A comprehensive assessment of physiological response of organisms upon ingestion of NMPs is therefore warranted. To be able to identify realistic threats that NMPs pose to organisms, we need more environmentally relevant research, especially focusing on agricultural soil. The main objective of this project is to investigate the impact of environmentally relevant NMPs on terrestrial invertebrates. Environmental relevance will be considered in terms of tested plastic particles, which will be derived from relevant materials commonly found in agricultural soil, and by subjecting NMPs to environmental weathering. We will address the following main issues: (i) sublethal physiological responses of organisms to NMPs exposure, with particular focus on immune-related processes, (ii) identify the probable adverse outcome pathways related to NMPs, (iii) contribution of environmental aging to adverse effects of NMPs, (iv) the difference between the hazard posed by nanoplastic vs microplastics. The project will comprise of three methodological parts: supply of NMPs and physico-chemical characterisation, weathering of NMPs and the study of adverse effects on terrestrial organisms. Nano- and microplastics will be milled from plastic source materials (tyres, agricultural plastic mulch and textile) using appropriate planetary ball mills. Also, NMPs will be supplied by external partner from Vrije Universiteit Amsterdam. Physico-chemical characterisation will include the size analysis, surface topology, shape, polymer composition and leaching analysis from NMPs. Accelerated weathering which simulates damaging effects of long-term outdoor exposure of polymers will be done according to established protocols already employed as regular testing approaches for polymer accelerated aging. Terrestrial organisms with different ecological roles and soil niches will be studied: the woodlice P. scaber, white earthworm E. crypticus and mealworm beetle T. molitor. They will be exposed to NMPs via soil exposure and afterwards whole-organism endpoints such as the feeding rate, growth, energy reserves and survival will be followed. The ingestion, fragmentation and retention of microplastics in the gut will be investigated using light and electron microscopy. Immune-related parameters will be followed using spectrophotometric analysis and expression of selected immune-related genes. Proteome analysis of haemolymph will also be done to complement gene expression analysis interpretation as well as to elucidate antioxidant and detoxification processes. Feasibility of the project will be ensured by highly-skilled international interdisciplinary team. The core team from the Department of Biology at Biotechnical faculty will cooperate with the Department of Animal Sciences (BF), Institute “Jožef Stefan” and Slovenian national building and civil engineering institute. Two external partners from EU; Vrije Universiteit Amsterdam, and the SYKE Finnish Environment Institute; will importantly contribute to the proposed project work. Knowledge regarding microplastics effects on terrestrial organisms will contribute to in-depth understanding of potential hazard posed by nano and microplastics. The data delivered by this project will be useful in environmental risk assessment frameworks. The project will also reveal important biological understanding about the link between the alterations induced in digestive system and modulation of immune-related processes. The results of this project will greatly influence the field of NMPs environmental safety research.