SYMPOSIA PAPER Published: 01 January 1984

Toxicity Testing with Constant or Decreasing Concentrations of Chemically Dispersed Oil


An exposure system and method of quantitating toxicity have been developed to provide an estimate of the effects of dispersed oil on marine organisms under a variety of exposure conditions. Results of constant concentration exposures (for hours or days) can be compared to those of diluting exposures (decreasing to zero in 8 or 24 h) on a basis of the “toxicity index.” This index is equal to the total exposure when time in hours or days is multiplied by the concentration at each hour (ppm · h or ppm · days). Tests have been conducted with shrimp (Pandalus danae), two oils (Prudhoe Bay crude and a light Arabian crude), and two dispersants. There is a seasonal pattern to the tolerance of the shrimp. Tests in the colder months (fall/winter) produce toxicity indices approximately three times higher than summer/spring values. Testing shrimp with Prudhoe Bay crude oil and a chemical dispersant during the fall/winter season, we found constant and 24-h dilution exposures produced toxicity indices of 11 (±1.1 standard error) and 10 (±0.6 standard error) ppm · days, respectively. During the fall/winter season (greatest tolerance), tests with Prudhoe Bay crude and two different chemical dispersants produced toxicity indices for P. danae of 10 (±0.6) and 12 (±1.1) ppm · days. During tests in summer, there was also little difference observed when the toxicity of the light Arabian oil was compared to that of Prudhoe Bay crude (2.3 and 3.4 ppm · days, respectively). The usefulness of our methods is that in addition to the comparisons already noted, it is possible to predict the outcome of dispersant application under varying environmental conditions.

Author Information

Anderson, JW
Kiesser, SL
McQuerry, DL
Riley, RG
Fleischmann, ML
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Developed by Committee: F20
Pages: 14–22
DOI: 10.1520/STP30225S
ISBN-EB: 978-0-8031-4906-9
ISBN-13: 978-0-8031-0400-6