Effects of water dispersions and water-soluble fractions of two crude and two processed oils on three marine algal species.

Three marine algal species, Isochrysis galbana Parke (haptophyte), Glenodinium halli Freudenthal and Lee (dinoflagellate) and Cyclotella nana Hustedt (diatom) were exposed to the water-soluble fractions (WSF) and oil-in-water dispersions (OWD) of four American Petroleum Institute reference petroleums; a Kuwait crude, a South Louisiana crude, a #2 fuel oil and a Bunker C fuel oil. Tests were conducted in 72-hour static cultures and effects were noted by measuring changes in population growth rates and chlorophyll a levels. Infrared measurements were made to determine the actual dissolved petroleum levels in the WSF and values found were: Kuwait crude, 20 ppm; Lousiana crude, 15 ppm; #2 fuel oil, 10 ppm; and Bunker C, 10 ppm. The concentrations of the test materials (OWD and WSF) required to reduce growth rates and chlorophyll a levels to 50% of the same parameters in the untreated controls (EC50 level) indicated that the two refined products (#2 fuel oil and Bunker C oil) were more toxic then the two crude oils. Moreover, Kuwait crude appeared less toxic than Louisiana crude. The responses of the three test organisms were very similar to the four petroleum products. Subcultures of organisms from treated cultures showing marked reductions in growth rates after incubation in fresh medium for 6 to 7 days. The relative toxicity of the petroleum WSF was not apparently related to the dissolved hydrocarbon concentrations but rather to the enrichment of the aqueous phase with aromatic compounds, specifically the naphthalenes.