AbstractContinuous‐flow toxicity tests using the oil dispersant Corexit 9527s̊ were performed on the early life stages of four California marine species. Newly released zoospores of the giant kelp,Macrocystis pyrifera, embryos of the red abalone,Haliotis rufescens, 4‐d‐old juveniles of the mysid,Holmesimysis costataand 10‐d‐old larvae of the topsmelt,Atherinops affinis, were all used in triplicate 48‐ and 96‐h tests. Quantitative verification of dispersant concentrations using UV spectrophotometry was performed twice daily during testing. Results indicated growth of kelp gametophytes was significantly reduced at<2.4 ppm after a 48‐h exposure. Of the three animals tested, developing red abalone were the most sensitive (NOEC = 0.63 to 1.50 ppm; LC50 = 1.60 to 2.20 ppm). Mysid juveniles were intermediate in sensitivity (NOEC = 1.66 to 4.20 ppm; LC50 = 4.26 to 7.26 ppm), whereas topsmelt larvae were the least sensitive (NOEC = 12.27 to 14.18 ppm; LC50 =25.51 to 40.63 ppm). Reproducibility of test data was very high (coefficient of variation
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