Hazard assessment of a mixture of pharmaceuticals detected in the upper Tennessee River of Daphnia magna and the determination of riverine zooplankton assemblage as it relates to chitobiase activity

In order to respond to the need for hazard assessment of environmentally relevant pharmaceutical mixtures, 21-d life cycle tests were performed on a mixture of pharmaceuticals found in the Tennessee River using Daphnia- magna as a surrogate. Endpoints measured were time to first brood, reproduction, mortality, and number of neonates produced per adult reproduction day. Reproduction was the only endpoint that showed a significant effect. The LOEC of the pharmaceutical mixture was found at 100 times (100x) greater concentration (p=0.005) than what was detected in the Tennessee River. Similarly, the NOEC was 75x (p=0.150). Single concentrations of pharmaceuticals within the mixture up to the LOEC were found to have no effect. Thus, no single pharmaceutical was responsible for the mixture LOEC. To determine if chitobiase can be used to predict secondary production, chitobiase activity and zooplankton density and biomass samples were measured in six Tennessee River tributaries