Occurrence of Microplastics in the Sediments of an Irish River and Their Effects on Nematode Survival and Biodiversity

Microplastics (MPs), defined as plastic particles of 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 (POPs), like polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), raising concerns about their impact on biota. To elucidate this impact, the present study employed attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to analyse the characteristics of MPs sourced from commercial cosmetics. We investigated the toxicity of MPs 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 MPs and other pollutants, including atrazine, 1,3-dichloropropene, naphthalene, and fluorene, in controlled settings over 72 to 96 h. Additionally, high-throughput 18S rDNA sequencing was used to analyse nematode biodiversity in sediments from the River Barrow (RB) in SE Ireland. Our findings revealed that MPs increased nematode mortality and adversely affected community structure, as indicated by nematode maturity and sigma maturity indices, suggesting a potential disruption of the ecological balance in river sediments. This highlighted the ecological risks posed by MP pollution and emphasised the urgent need for further research into the health of benthic ecosystems in Ireland, particularly in relation to how MPs may influence nematode community dynamics and biodiversity.