Profiling accumulated PAHs and metabolomic responses in truncate soft-shell clam (Mya truncata) in the Canadian Arctic

Arctic ecosystems face many contamination challenges due to increasing human development and long-range atmospheric transport. Among these contaminants of concern are polycyclic aromatic hydrocarbons (PAHs) due to their variety of natural and anthropogenic sources related to oil spills and the combustion of organic substances. As a result, PAHs present a potential threat to Northern communities that harvest local species for food, which may accumulate or be negatively impacted by PAHs. To address these concerns, this study quantified the impacts of PAHs on an important locally harvested food source by quantifying contaminant burdens in the marine clam Mya truncata, collected from Frobisher Bay near the city of Iqaluit, Canada. Metabolomic responses were assessed to identify common biomarkers of PAH stress to further develop M. truncata as a biomonitor species. Σ₅₂ PAH burdens were 20.5 ± 0.8 ng·g^-1 ww in clams collected close to Iqaluit's wastewater treatment plant discharge, decreasing to 10.6 ± 1.1 ng·g^-1 ww ∼3 km away. Diagnostic ratios indicate that these PAHs are from a mixture of pyrogenic and petrogenic sources, dominated by a large diversity of alkylated PAHs. Clams were able to compensate for contaminant burdens as no changes in physiological characteristics were observed between study sites. Metabolomic analyses revealed a signature of increased glutathione production for possible antioxidant activities, and an increase in aerobic and anaerobic metabolism. Due to the non-detection of the most toxic PAHs as well as the low accumulated burdens, the threats of PAH contamination to M. truncata in the region appear relatively low.