Multiple ecotoxicological effects of sublethal exposures to atmospheric particulate matter in two neotropical benthic...

Settleable atmospheric particulate matter (SePM) constitutes a significant source of pollution in aquatic ecosystems, primarily due to the introduction of various metals, mainly resulting from emissions from metallurgical industries. However, its adverse effects on aquatic biota have not yet been widely understood, especially for species that inhabit the benthic region of freshwater ecosystems. This study evaluated the sublethal effects of environmentally relevant concentrations of SePM on growth and reproduction as individual- and population-level endpoints, as well as biomarkers of antioxidant defense, oxidative stress, and cellular damage in the oligochaete Allonais chelata (Tubificida: Naididae) and the larval stage of the insect Chironomus sancticaroli (Diptera: Chironomidae), species widely used in ecotoxicology due to their sensitivity to contaminants and ecological relevance in benthic environments. Larvae of C. sancticaroli were exposed for 8 days at increasing concentrations from 0.001 to 1 g L⁻¹ of SePM, while A. chelata was exposed for 32 days at 0.01-1 g L⁻¹ of SePM. After the exposure period, biomarkers related to antioxidant defense, oxidative stress, and cellular damage were evaluated. Furthermore, the growth of C. sancticaroli larvae and the growth and reproduction of A. chelata were assessed. The results showed that, although no lethal effects of SePM exposure were observed, reductions in the reproduction of A. chelata occurred, as well as an increase in biomass gain. For C. sancticaroli, a decrease in size and biomass gain was also observed, along with clear ingestion of SePM by both species. Furthermore, all evaluated markers were altered in C. sancticaroli, whereas in A. chelata, the most evident changes were observed in the levels of metallothionein, superoxide dismutase, reduced glutathione, and lipid peroxidation. The results of this study highlight the negative impacts of SePM on two aquatic invertebrates, providing clear evidence of the problem of its continued deposition and reinforcing the need for systematic environmental monitoring to assess its effects at different trophic levels in the long term.