The Toxicity of Crude Oil and its Components to Freshwater Algae

Abstract

ABSTRACT Field and laboratory experiments have been conducted to determine the toxicity of crude oil to freshwater algae. In the field, experiments were continued for a two year period and changes in the abundance and species composition of phytoplankton tabulated. Species were found to differ markedly in their response to an oil spill—varying from considerable suppression of growth to stimulation. In the laboratory, the effects of aqueous extracts of seven crude oils on a selected test species, Chlorella vulgaris, were determined. Marked differences in toxicity, as indicated by reduced growth, were found to exist between oils. Work with oil extracts of different ages suggests that the short-term toxicity of oils is due to the rapid loss of volatile compounds. Differences in the toxicity of selected aromatic components of crude oils—benzene, toluene, o-xylene and naphthalene—were observed and are believed to relate to an increase in methylation. Aqueous crude oil and naphthalene depressed the 14C-NaHC03 uptake (i.e. photosynthesis) of Chlamydomonas angulosa. 14C-naphthalene was rapidly taken up by Chlamydomonas cells. However, release of this compound was much slower, and, in unwashed cells, seemingly dependent upon cell division. Possible mechanisms of crude oil toxicity are discussed.