Periphyton, bivalves and fish differentially accumulate pharmaceuticals in effluent-dependent stream mesocosms

Abstract Pharmaceuticals and other ionizable contaminants from municipal wastewater treatment plant effluent can bioaccumulate in fish, particularly in effluent dominated and dependent systems in semi-arid and arid regions. However, invertebrate bioaccumulation of these compounds is less defined. Using municipal wastewater effluent in outdoor stream mesocosms to simulate effluent-dependent lotic systems, we examined bioaccumulation of several widely-used pharmaceuticals including acetaminophen (nonsteroidal anti-inflamatory), caffeine (stimulant), carbamazepine (anti-epileptic), diltiazem (calcium channel blocker), diphenhydramine (anti-histamine), fluoxetine (anti-depressant), norfluoxetine (anti-depressant metabolite), and sertraline (anti-depressant) by freshwater clams (Corbicula fluminea), periphyton and stoneroller minnows (Campostoma anomalum), a commonly studied grazer in stream ecology, during a replicated outdoor stream mesocosm study at the Baylor Experimental Aquatic Research facility. Target analytes were determined in tissues, source effluent and stream water by isotope dilution LC-MS/MS. After an 8-day uptake period, clams accumulated a number of pharmaceuticals, including acetaminophen, carbamazepine, diltiazem, diphenhydramine, fluoxetine, norfluoxetine and sertraline with maximum concentrations reaching low μg/kg. Clams showed uptake rates of acetaminophen at 2.8 μg/kg per day, followed by diphenhydramine (1.2 μg/kg per day) and carbamazepine (1.1 μg/kg per day). Caffeine, carbamazepine, diltiazem and diphenhydramine were observed in periphyton. Diphenhydramine was the only compound detected in all matrices, where bioaccumulation factors (BAFs) were elevated in bivalves (1631 ± 589 L/kg), compared to stoneroller minnows (247 ± 84 L/kg) and periphyton (315 ± 116 L/kg). Such BAF variability across multiple biological matrices highlight the need to understand bioaccumulation differences among freshwater biota, including threatened and endangered species (e.g., unionids), commercially important bivalves (e.g., estuarine and marine bivalves), and fish.