The objectives of this program were to evaluate the toxicity of nine metals to cultures of four species of marine phytoplankton. The relationships of acute, instantaneous and chronic toxicity were evaluated using growth rates in continuous-flow culture systems. The latter methods employed both the chemostat and the turbidostat techniques. The instantaneous procedure measures short-term changes of metabolic activity indicated by 14-C uptake that result from metal addition within a relatively short time period after cultures are exposed to metal additions. Four levels were determined for the acute toxicity of metals to each organism. The use of fluorometric measurements of relative chlorophyll-a of actively growing cultures was a fast, accurate assay method that facilitated the Minimum Toxicity Level calculation, increased the sensitivity of the method, and reduced variability. Refinement should result in this method being more useful for giving more uniform assay results.

"Study conducted in cooperation with Marine Research Laboratory, Texas A & M University at Galveston." "February 1980." "Project Officer: C. S. Hegre." Includes bibliographical references (pages 81-91). "Grant No. R801511."