Baseline assessment of microplastics and biochemical response of Anadara antiquata as a sentinel species for biomonitoring in Fiji

Context Microplastics are a concern for maritime nations such as Fiji, which rely heavily on seafood, such as bivalves, which can transfer pollutants through the food chain. The lack of biomonitoring studies in the Pacific region highlights the necessity of researching microplastic pollution in seafood. Aims This study quantifies microplastics in Anadara antiquata, a commonly consumed shellfish in Fiji, and evaluates its general biochemical responses. As a baseline, this study is not to draw an association between the two endpoints (microplastics and biochemical responses), rather present these as baselines for future studies. Methods A total of 58 specimens from Ba River Delta, Rakiraki Bay and Vueti Navakavu were examined, where differences in potential sources or pathways for microplastics, including anthropogenic pollutants with the potential to induce stress on marine animals, were considered (rivers, industrial zones, stormwater outlets, sewerage outfalls and mining area). Specific hepatopancreatic enzyme activities associated with detoxification (glutathione-S transferase, GST) and oxidative stress (glutathione peroxidase, GPX, and glutathione reductase, GR) were measured. Key results Microplastics were extracted, classified by morphology and quantified. The study found that 64% of specimens had microplastics, <1.0 mm being more prevalent. Ba River Delta showed significant biochemical stress (Kruskal–Wallis test; P < 0.05) with GST (χ2 = 40.28, d.f. = 2, P-value < 0.001), GPX (χ2 = 38.38, d.f. = 2, P-value < 0.001) and GR χ2 = 45.14, d.f. = 2, P-value < 0.001) being considered as likely to be responding to pollution. Conclusion As a baseline, the study underlines the need for biomonitoring as a result of varying and concerning levels of pollution and biochemical stress responses found across the study areas. Integrating biomonitoring methods into risk-assessment protocols in Fiji may support establishment of opportunities or considerations for health guidelines and policy interventions to minimise human exposure to microplastics, and regulate environmental pollution. Implications These measures are crucial for protecting public health and monitoring pollution impacts.