The ecological risk dynamics of pharmaceuticals in micro-estuary environments

Micro-estuarine ecosystems have a surface area < 1 km2 and are abundant in Mediterranean regions. As a result of their small size, these systems are particularly vulnerable to effects of chemical pollution. Due to fluctuating flow conditions of base-flow dominated by treated wastewater effluents and flood events transporting rural and urban non-point-source pollution, micro-estuaries are under a dynamic risk regime, consequently, struggling to provide ecological services. This two-year study explored the occurrence and risks of pharmaceutical contamination in the Alexander micro-estuary in Israel. Pharmaceuticals were detected in all samples (n=280) at as high as 18 µg L-1 in flood events and 14 µg L-1 in base-flow. Pharmaceutical mixtures composition was affected by flow conditions with carbamazepine dominating base-flow and caffeine dominating flood events. Median annual risk quotients for fish, crustaceans and algae were 19.6, 5.2, and 4.5, indicating that pharmaceuticals pose high risk to the ecosystem. Ibuprofen, carbamazepine and caffeine were contribute most to the risk quotients. The current work highlights that micro-estuary ecosystems, like the Alexander estuary, are continuously exposed to pharmaceuticals and most likely to other pollutants, placing these ecologically important systems under an elevated risk, in comparison to the more frequently studied large estuarine systems.  .