Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Environmental Toxicology

Committee Chair/Advisor

Klaine, Stephen J.


Land use change results in significant amounts of soil migrating into aquatic streams during storm events. This suspended sediment, even in the absence of adsorbed contaminants, may be a significant stressor to aquatic organisms. The data on ecological effects of suspended sediment has mainly focused on salmonids or ecosystem level consequences such as habitat alteration. Few studies have quantified physiologic effects of suspended solids on water column organisms. The purpose of this research was to determine the effects of suspended clay on Daphnia magna and Pimephales promelas. Results of 7 d toxicity tests with D. magna in natural and defined clay suspensions indicated LC50 values ranging from 5 mg/L to 75 mg/L with montmorillonite being more toxic than kaolinite. Gill Na+/K+-ATPase levels in P. promelas decreased as a function of exposure duration to 1,000 mg/L suspended montmorillonite. These results underscore the need to consider physical stressors in watershed risk assessment.



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