New testing apparatus for assessing interactive effects of suspended solids and chemical stressors on plankton invertebrates

To better predict and interpret the responses of aquatic organisms to envir onmentally relevant chemical exposures, it is necessary to investigate the combined effects of physical (e.g., suspended solids) and chemical stressor s. One of the limitations in investigating suspended solids-chemical intera ctions has been the lack of an appropriate testing system. The specific obj ective of the current study was to develop and assess a suspended solids te sting apparatus (SSTA) for studies on the combined effects of suspended sol ids and chemicals on aquatic invertebrates. The SSTA was designed to permit the assessment of varying suspended solids concentrations on Daphnia magna at a constant freely dissolved concentration of a compound. The system was also designed to facilitate the control of exposure variables without the need for large numbers of replicates and chemical analyses. The experiments reported here demonstrate that the SSTA is effective for assessing the com bined or interactive effects of suspended solids and a chemical stressor on aquatic organisms.