The importance of scale : bioaccumulation of contaminants of emerging concern by bivalves.


Increasing urbanization presents unique challenges to sustainable environmental quality, particularly in urbanizing arid and semi-arid regions of the United States (U.S.). In urban areas, municipal wastewater treatment plants discharge treated effluent directly to streams, and total stream flow is often dominated by or dependent on wastewater effluent. As a result, contaminants of emerging concern (CECs), which are present in wastewater effluent, are discharged directly to the receiving streams. This has led to a rapidly developing literature for environmental assessment and management of various down-the-drain contaminants. However, most environmental methods focus on measuring pharmaceuticals in water, sediments and fish. A large data gap exists for accumulation of CECs, including pharmaceuticals and personal care products (PPCPs), in bivalves. Filling this data gap is important because bivalves are valued both ecologically and economically; Bivalves are known to improve water quality via their capacity to filter particulate matter from the water column, and bivalve aquaculture operations support local economies and serve as an additional source of food. To capitalize on available suspended particulate matter, these aquaculture platforms are often located in wastewater treatment plant discharge areas, potentially exposing the bivalves to contaminants that can accumulate in their tissue. The results in this dissertation have filled several data gaps related to bioaccumulation of PPCPs by bivalves. First, results from a pilot study in Hong Kong showed that bivalves from both large-scale and small-scale aquaculture operations accumulated low levels of CECs. Second, results from a field-study in an effluent-dependent stream indicated that bivalves accumulated several different types of pharmaceuticals, in some cases reaching steady-state after 8 days exposure, and spatial differences were observed for some compounds, with highest observed concentrations for antidepressants. Third, results from an outdoor mesocosm experiment highlighted different uptake patterns for bivalves during the first 7 days of exposure to treated wastewater, and indicated that bivalves accumulated a greater number of pharmaceuticals when compared to fish in the same streams. Finally, results from a laboratory study highlighted different uptake and elimination patterns for two commonly detected pharmaceuticals.



Bioaccumulation. Pharmaceuticals. Bivalves. Uptake.