Multi‐Biomarkers' Responses in Gills of Oreochromis niloticus Exposed to Glyphosate and Polyethylene Microplastic, Isolated and in Mixture

ABSTRACT Microplastics (MPs) and glyphosate‐based herbicides (GBH) are among the most common contaminants in aquatic environments. In Brazilian rivers, both contaminants were found in elevated levels, leading to a high probability of their association, which can alter their individual effects and potentially intensify their toxicity. This study evaluated the isolated and combined effects of polyethylene microplastics (PE‐MPs) and GBH on Oreochromis niloticus using multi‐biomarkers of toxicity. The fish were subjected to a 96‐h exposure period, with concentrations set based either isolated, PE‐MPs group (5 mg L −1 ), GBH group (5 mg L −1 ), or in a group of associated contaminants (GAC), PE‐MP + GBH (5 mg L −1 + 5 mg L −1 ). Toxicity effects were evaluated using biochemical, cytogenetic, hematological, and histopathological biomarkers. We observed change in erythrocyte parameters leading to macrocytic normochromic anemia in GAC. Leukocyte parameters indicate a nonspecific immunosuppression caused by the exposure of associated contaminants, besides the attempts to repair damage caused by PE‐MPs. Histopathological markers indicate damage to tissues exposed to contaminants. Besides, there were morphophysiological adjustments on gills, with proliferation and hypertrophy of mitochondria‐rich cells on GBH and GAC, besides epithelium ruptures, which were mostly present in the exposed groups. Therefore, this study indicates that PE‐MPs and GBHs present toxic effects in O. niloticus with the used concentrations, intensified by the association of contaminants. Thus, multi‐biomarkers were useful key to verify toxicity, providing data to the investigation of high levels of contaminant's mixture toxicity present in aquatic environments.