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 environmentally relevant chemical exposures, it is necessary to investigate the combined effects of physical (e.g., suspended solids) and chemical stressors. One of the limitations in investigating suspended solids–chemical interactions has been the lack of an appropriate testing system. The specific objective of the current study was to develop and assess a suspended solids testing apparatus (SSTA) for studies on the combined effects of suspended solids 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 combined or interactive effects of suspended solids and a chemical stressor on aquatic organisms. Keywords—Suspended solids Carbofuran Daphnia magna Acute toxicity Mixture effects