Pharmaceutical pollution in a wastewater-impacted coastal ecosystem

As global demand for pharmaceuticals continues to grow, pharmaceutical pollution is becoming increasingly pervasive. Research on the occurrence and distribution of pharmaceuticals in marine ecosystems remains limited, however, with coastal sewage outfalls considered to be a major source of pharmaceutical pollutants in marine environments. Here, we investigated the distribution of pharmaceuticals across a wastewater gradient in Port Phillip Bay, Melbourne, Australia, using stable nitrogen isotope ratios (δ¹⁵N) as a signal of wastewater influence. Marine invertebrates, macroalgae and marine/terrestrial plants were sampled across four sites of varying distances from Melbourne's largest wastewater treatment plant and analyzed for δ¹⁵N and pharmaceuticals. Out of 95 target analytes, 15 were detected, with the most frequent detections being telmisartan (83%), flecainide (52%), memantine (37%), caffeine (28%) and tramadol (23%). Pharmaceutical concentration was positively associated with δ¹⁵N, supporting wastewater influence as a key driver of pharmaceutical pollution. Interestingly, concentrations were highest in primary producers, including terrestrial plants. Follow-up sampling revealed higher pharmaceutical concentrations in sea foam relative to seawater, suggesting enrichment within the air-water interface and potential transport to terrestrial environments via coastal aerosols. Overall, our findings demonstrate the role of wastewater in pharmaceutical pollution, with plants and algae emerging as potential bioindicators.