Comparative effects of oil dispersants to the early life stages of topsmelt (Atherinops affinis) and kelp (Macrocystis pyrifera)

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Abstract
The acute effects of two oilspill dispersants were compared using the early life stages of two common nearshore marine organisms the topsmelt (Athennops affinis), a common fish in bays and estuaries, and the giant kelp (Macrocystis pyrifera), a canopy forming brown alga Testing was done under closed, flow through conditions, with spiked dispersant concentrations measured in real time using UV spectrophotometry Both dispersants were composed of complex mixtures of anionic and nonionic surfactants and solvents Median effect concentration data showed Athennops tests to be more sensitive to both dispersants than Macrocystis tests, with values ranging from 48 2 to 72 9 ppm (LC50) and 73 0 to 79 4 ppm (IC50), respectively, for Nokomis® 3, and from 43 7 to 45 8 ppm (LC50) and 73 0 to 95 9 ppm (IC50), respectively, for Slik A Way A different pattern was seen in NOECs, in which both species showed significantly higher sensitivity to Slik A Way than to Nokomis 3 (α = 0 05) Comparison of the present data with those previously compiled for the same products with two other species the red abalone (Hahotis rufescens) and a mysid (Holmesimysis costata), showed fairly consistent interspecific patterns among three of the four species, Holmesimysis tests were seen to be least sensitive to Nokomis 3 and second most sensitive to Shk A Way In addition, Shk A Way was more toxic to all species except Macrocystis