The toxic impacts of microplastics-borne benzo[a]pyrene and heavy metals on the health and behavior of seahorse Hippocampus erectus

Marine pollution poses a critical threat to biodiversity. The synergistic effects of microplastics, specifically high-density polyethylene (HDPE), combined with benzo[a]pyrene (B[a]P) and heavy metals, on the physiology and feeding behavior of the seahorse, Hippocampus erectus were studied. The growth parameters, pollutant bioaccumulation, enzymatic response, and feeding dynamics were extensively analyzed. Seahorses exposed to microplastics-borne B[a]P and heavy metals exhibited notable reductions in body length and weight, as well as in survival rates, indicating severe stress from these contaminants. The accumulation of pollutant particularly B[a]P in seahorse exceeded China’s national regulatory limit of 5 µg/kg, and the B[a]P accumulation in seahorses was obviously aided by HDPE microplastics, posing a risk to marine organisms and human health via the food chain. The adaptive response of the seahorses was evident shown in the elevation of antioxidant enzyme activities, which is a biological mechanism to mitigate oxidative stress induced by the pollutants. However, this physiological adaptation comes at a cost, as evidenced by marked changes in the feeding behavior. Results show that the efficiency and frequency of feeding were greatly reduced, indicating a heavy impact on the ecological role and survival of this marine creature in polluted habitats. This research offers a crucial perspective on the compound threats of microplastics and associated pollutants in marine ecosystems. It highlights the urgent need develop comprehensive strategies to address these environmental issues. The findings are an important contribution to ecotoxicology, providing a deeper understanding of how microplastics act as vectors for other contaminants and their profound effects on marine life, especially species like seahorses. This study calls for action to strengthen environmental policies and practices aimed at mitigating the impact of marine pollution.