Microplastic-induced reductions in population abundance and body size of soil nematodes

Microplastics (MP) pose potential harm to the environment and human health. However, only a few known studies focus on the size-dependent effects and toxicity of microplastics on soil-dwelling nematodes. In this study, we investigated the effects of micropolystyrene particles with diameter sizes of 0.1 μm, 0.5 μm, and 1 μm on the population abundance, and body size of the three soil nematodes, Cephalobus sp., Cervidellus vexilliger, and Mesorhabditis sp., isolated from Davao de Oro in southern Philippines. After 45 days of exposure to MP of different sizes, the three nematode species showed significant decreases in their population abundance. For the body size parameters, a significant decrease was observed in the body lengths of the three nematode species and the body volume of Cephalobus sp. when exposed to the different MPs sizes. Among the three MP sizes, 0.1 μm yielded the most profound impact on the nematode responses, resulting in significant decreases in the mean population abundance, and body size of the three species. These findings demonstrate that microplastic particles can cause size-dependent toxicity to soil-dwelling nematodes’ physical and biological characteristics, posing deleterious effects to these organisms.