The purpose of this study was to assess the effects of water-soluble fractions (WSF) of naphthalene, phenanthrene, No. 2 fuel oil, and coal-tar creosote on the survival, growth, reproduction, feeding, and metabolism of Daphnia pulex. The 48 hr LC50 values after acute exposure (as percent WSF) for creosote, No. 2 fuel oil, phenanthrene and naphthalene were 2.91, 34.10, >>100, and 57.52 percent, respectively. Gas chromatography analysis indicated naphthalene and phenanthrene 48 hr LC50 values (as mg/1) were 2.92-3.89 and 0.96-1.28, respectively. Up to 40 peaks were noted in each stock WSF of creosote and No. 2 fuel oil. For chronic studies, young (24 hr) Daphnia were exposed to calculated LC20 and LC30 concentrations of WSF's for their entire life. The LC30 concentrations of creosote and phenanthrene showed a significant reduction in growth rate and number of live young, as well as reduced number of broods, impairment of molting, and significant delay in reproductive maturation; instances of possible neoplasms were also noted in one organism from each of these test groups. No. 2 fuel oil produced similar effects on growth and reproduction, but results were not as significant. Increased longevity and slight reduction in growth rate were noted for both naphthalene test groups. The effects upon oxygen consumption after exposure to test WSF's were variable. The LC30 concentration of creosote and both naphthalene concentrations were significantly different from each other; both naphthalene concentrations elicited the lowest oxygen consumption rates recorded, while the creosote LC30 group exhibited the highest rate of oxygen consumption. However, no experimental means were significantly different from controls. Highly significant differences existed between filtering rates of organisms after exposure to the WSF's. The LC20 concentrations of creosote and phenanthrene produced the highest and lowest filtering rates, respectively. Both oil test groups demonstrated significantly higher filtering rates. Monitoring zooplankton filtering rates appears to be a promising parameter to evaluate physiological stress on these organisms. This chronic study and data from other comparable chronic studies indicate that the length of a pre-adult Daphnia after 7 days of exposure to stress can be used to predict chronic reproductive effects with the same degree of accuracy as the 21-day test. Adoption of this test would eliminate difficulties with starvation, nutrition, and competition for food which contribute to the variability in reproductive impairment tests. A possible mechanism of action of polynuclear aromatic hydrocarbons upon endocrine systems is strongly suggested by the dramatic and diverse effects upon growth and reproduction in Daphnia pulex. / Ph. D.