Corbicula fluminea rapidly accumulate pharmaceuticals from an effluent dependent urban stream

Freshwater bivalve populations are stressed by watershed development at the global scale. Though pharmaceuticals released from wastewater treatment plant effluent discharges are increasingly reported to bioaccumulate in fish, an understanding of bioaccumulation in bivalves is less defined. In the present study, we examined accumulation of 12 target pharmaceuticals in C. fluminea during a 42 day in situ study in Pecan Creek, an effluent dependent wadeable stream in north central Texas, USA. Caged clams were placed at increasing distances (5 m, 643 m, 1762 m) downstream from a municipal effluent discharge and then subsampled on study days 7, 14, 28 and 42. Acetaminophen, caffeine, carbamazepine, diltiazem, diphenhydramine, fluoxetine, norfluoxetine, sertraline, desmethylsertraline, and methylphenidate were identified in C. fluminea whole body tissue homogenates via isotope dilution liquid chromatography-tandem mass spectrometry. Tissue concentrations ranged from low μg/kg (methylphenidate) to 341 μg/kg (sertraline). By study day 7, rapid and apparent pseudo-steady state accumulation of study compounds was observed in clams; this observation continued throughout the 42 d study. Notably, elevated bioaccumulation factors (L/kg) for sertraline were observed between 3361 and 6845, which highlights the importance of developing predictive bioaccumulation models for ionizable contaminants with bivalves. Future research is also necessary to understand different routes of exposure and elimination kinetics for pharmaceutical accumulation in bivalves.