Bioassays with a Natural Assemblage of Benthic Macroinvertebrates

A new bioassay method for determining the effects of environmental contaminants on populations of benthic macroinvertebrates is described. Colonized Hester-Dendy samplers were transported from a natural stream to artificial streams and exposed to industrial wastewater. Species diversity, number of taxa, and density of the aquatic organisms were measured before and after selected time intervals of exposure. A 30 and a 32-day continuous-flow exposure test with the benthic macroinvertebrates showed that activated sludge treated petroleum refinery wastewater caused a greater decrease in species diversity than the sequential activated sludge-dual media-activated carbon treated effluent. The effect upon number of taxa and mean density of individuals was even greater.

This procedure permitted exposure of several species of aquatic invertebrates to the test solution and thus measured the effect upon pollution-sensitive and tolerant organisms.