Some Factors Influencing Toxicity of Linear Alkylate Sulfonate (LAS) to the Bluegill

Some factors influencing toxicity of linear alkylate sulfonate (LAS) on the early life history stages of the bluegill, Lepomis macrochirus (Rafinesque), were studied in raw Mississippi River water under ambient conditions and under controlled conditions in well water. Median response varied from 0.2–10 mg/1 LAS with the life history phase and environmental conditions. Variation in estimation of TLm values within and between similar tests was small in comparison to the influence of external factors. The most important environmental factors related to lethal threshold concentration of LAS were dissolved oxygen, water hardness, and acclimation to LAS. High temperature decreased the median tolerance limit only during tests of short exposure. Sublethal concentrations of LAS increased toxicity of fuel oil mixtures while bentonite suspensions up to 200 mg/1 had little influence on LAS toxicity. The most sensitive stage of development was the feeding sac-fry, while the most tolerant stage was the newly hatched sac-fry. Eggs and fingerlings had similar intermediate tolerance limits. Egg fertilization was the least inhibited of the events studied. A concentration of 1 mg/1 LAS is considered to be a first approximation of a safe concentration for bluegills in Mississippi River water of good quality.