The Effects of Exposing Solea senegalensis to Microbeads with and Without Pesticides

Abstract Microplastics (MP) are contaminants able to cause adverse effects on organisms. MPs are capable to interact with other environmental contaminants, including pesticides, altering their toxicity. The objective of the study was to research the sublethal effects (enzymatic activity) of pesticides alone and in combination with MPs. Cholinesterase enzymes are used as biomarkers to determine and evaluate the effects produced in organisms after exposure to pollutants. This study showed the acetylcholinesterase (AChE) enzymatic activity in the tissue of Solea senegalensis exposed to two environmental pollutants, the insecticide chlorpyrifos (CPF) and antibacterial triclosan (TCS) with and without microplastics (MPs). Solea senegalensis was chosen because it is a species in high demand because of its high economic value in southern Europe, as well as the use of this species in ecotoxicology and its increasing use as sentinel species, which justify using it to assess biological effects of pollutants. Toxicity tests were performed in organisms exposed to concentrations of between 5 and 80 μg/L CPF and 0.1 and 0.4 mg/L TCS for 96 h. In addition, each test incorporated MPs that were added at different concentrations in order to evaluate their role as a possible enhancer of the effects caused by the previous pollutants. In the case of CPF, the head and muscle tissue cholinesterase activity was inhibited from a concentration of 5 μg/L both without and with MPs, and the AChE enzymatic activity for the treatment with MPs was approximately half the activity for the treatment without MPs in the tissues studied. Besides, TCS inhibited the cholinesterase activity at a concentration of 0.3 mg/L in the muscle of S. senegalensis . In contrast, no significant differences were observed in the TCS + MP treatment compared to the controls. These results showed the importance of studies in assessing the anticholinesterase effects of pesticides combined with microplastics due to the abundance of these contaminants in the marine environment and the role of cholinesterase activity (biomarker) in the neurotransmission of key physiological processes.