Acute Toxicity of the Anionic Surfactant Dioctyl Sodium Sulfosuccinate to Eggs, Larvae, and Juvenile Gulf Killifish at Varying Salinities

Formulations of Corexit^®, a family of oil dispersants used in large scale oil spills, have been the primary emulsification agents utilized by industry and governmental agencies.  Although formulations are proprietary, the anionic surfactant dioctyl sodium sulfosuccinate (DSS) is a major component of several dispersants. Although the acute toxicity of these primary oil dispersants used for the past 25 years is well established in toxicology literature, the toxicity of DSS across salinity gradients is relatively unknown. No acute toxicity information exists for DSS in any early developmental periods for freshwater or saltwater fish. Literature on the acute toxicity of DSS to aquatic organisms is based primarily on freshwater toxicity testing of fingerling rainbow trout (Oncorhynchus mykiss), of which the most recent work was published 20 years ago.

This study investigates the acute toxicity of a primary oil dispersant component to eggs, larvae, and juvenile Gulf killifish (Fundulus grandis) across a range of environmentally relevant salinities. Specifically this work seeks to determine the 96-h median lethal concentration (LC50) values for DSS to eggs, 15-d posthatch (dph) larvae, and juvenile (0.5 g) Gulf killifish. Each bioassay consists of exposing newly fertilized eggs, 15-dph larvae, or 0.5-g juveniles to 5 treatment concentrations and a control with 4 replicates per treatment and 20 individuals per replicate. The influence of salinity was assessed within trials ranging from 0.4 to 32 ppt at increments of 8 ppt. A subsample of individuals were exposed and collected at 24 h intervals for immunohistochemistry samples to be prepared at a later date.

The 96-hr LC50 estimate for 15-dph Gulf killifish was 14.1 mg/L DSS at a salinity of 5 g/L. Gulf killifish have been chosen for this work as an economically important estuarine baitfish and as a representative model for marine species. Due to their wide range of salinity tolerance (0 to >40 g/L) we can investigate the toxicity of DSS throughout a range of saltwater conditions. DSS has been previously demonstrated to alter absorbption rates across membranes we believe that it might demonstrate increasing toxicity as salinity ranges from freshwater to full strength seawater. Continued testing will yield quick useable information on the effects of DSS on eggs, larvae, and juvenile marine fishes and will fill a knowledge gap within several fields of research.