Oxidative stress responses of microplastic-contaminated Gambusia affinis obtained from the Brantas River in East Java, Indonesia

The biological impact of microplastic (MP) contamination on freshwater biota has sparked interest. Microplastics are thought to have a high potential for toxicity, affecting organism metabolism. The goal of this study was to investigating the antioxidant indicators on the gills and digestive tract of Gambusia affinis fish in the Brantas River reacted to microplastic pollution. The obtained data was evaluated using path analysis. The digestive tract had much greater levels of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) than the gill. SOD concentration in the gills was 13.7 ± 5.3 U/mL, while SOD concentration in the digestive tract was 16.3 ± 3.6 U/mL. The CAT concentration in the gills (5.3 ± 2.9 ng/mL) was higher than the CAT concentration in the digestive tract (10.5 ± 2.8) ng/mL, while the MDA concentration in the gills (690.8 ± 135.6 mU/mL) was higher than the MDA concentration in the digestive tract (869.6 ± 122.2) mU/mL. MP abundance has a direct effect on SOD and MDA in the gills. Meanwhile, the quantity of MP in the digestive tract has a direct effect on SOD and CAT, which affects the development of the MDA response.