Effects of Microplastic Pollutants on Nematodes and Their Biodiversity in Irish River Sediments

Microplastics (MP), defined as plastic particles less than 5 mm, pose a significant global environmental threat, particularly in aquatic ecosystems, due to their persistence and potential harmful effects on wildlife and human health. They can absorb persistent organic pollutants (POP) like polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB), raising concerns about their impact on biota. To elucidate this, the present study employed attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to analyse the characteristics of MP sourced from commercial cosmetics. It also utilised nematodes, which are widely accepted indicators of environmental change. Indeed, despite the known risks of MP in aquatic habitats, knowledge of their effects on free-living and beneficial nematodes is limited. This study investigated the toxicity of MP on Caenorhabditis elegans and two entomopathogenic nematode species, Steinernema feltiae (the enviroCORE strain SB12[1]) and Steinernema carpocapsae (a commercial strain from e-NEMA) in laboratory bioassays. Nematodes were exposed to various concentrations of MP and other pollutants in controlled settings over 72 to 96 hours. Additionally, high-throughput 18S rDNA sequencing was used to analyse nematode biodiversity in sediments from the River Barrow (RB) in SE Ireland. Results revealed that MP adversely affected nematode survival and community structure, highlighting the ecological risks posed by MP pollution in river sediments and emphasizing the need for further research into the health of benthic ecosystems in Ireland.