A multiple biomarker approach to understand the effects of microplastics on the health status of European seabass farmed in earthen ponds on the NE Atlantic coast

The occurrence of microplastics (MPs) in aquaculture environments is a growing concern due to their potential negative effects on fish health and, ultimately, on seafood safety. Earthen pond aquaculture, a prevalent aquaculture system worldwide, is typically located in coastal and estuarine areas thus vulnerable to MP contamination. The present study investigated the possible relation between MP levels of European seabass (Dicentrarchus labrax) farmed in an earthen pond and its health status. More precisely, two groups of fish were established based on the lowest and highest number of MPs found collectively in their gastrointestinal tract (GIT), liver, and dorsal muscle: fish with ≤2 MP/g and fish with ≥4 MP/g. The intestinal integrity and oxidative stress biomarkers in the liver and dorsal muscle were evaluated in the established groups. No significant differences in the biometric and organosomatic parameters between groups were observed. The results indicated a significant increase in the number of acid goblet cells (GC) in the rectum of fish with higher MP levels (p = 0.016). Increased acid GC number may constitute a first defence strategy against foreign particles to protect the intestinal epithelium. No significant differences in oxidative stress biomarkers between the two fish groups were observed, namely in the activity of superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase in the liver, or in lipid peroxidation levels in the liver and dorsal muscle. The overall results suggest that MP levels were possibly related to an intestinal response but its potential implications on the health status of pond-farmed seabass warrant further investigation. Monitoring MP occurrence across stages of aquaculture production could help to elucidate the potential threats of MPs to fish health.