Assessing the Toxicity of Individual Aromatic Compounds and Mixtures to American Lobster (Homarus americanus) Larvae Using a Passive Dosing System.

Aquatic exposures to aromatic compounds (ACs) may be important contributors to biological effects of oil spills. The present study examined the acute toxicity of 11 ACs and 3 binary AC mixtures on stage 1 American lobster larvae using a passive dosing test design. The ACs investigated covered a range of classes and log octanol-water partition coefficient values (K ; 2.5-5.5). Silicone O-rings were used to partition ACs into seawater and maintain stable exposures. Exposed lobster larvae were assessed for mobility and survival at 3, 6, 12, 24, 36, and 48 h. Fluorometry and gas chromatography-mass spectrometry measurements confirmed well-defined substance exposures. Expressing lethality in terms of chemical activities yielded values between 0.01 and 0.1, consistent with a baseline mode of action. Analysis of time-dependent median lethal/effect concentration (L/EC50) values were used to determine incipient values. An expected linear relationship between the incipient log L/EC50 and log K was fit to the empirical toxicity data to derive critical target lipid body burdens for immobilization and lethality endpoints. These values indicate that American lobster larvae fall on the sensitive end of the acute species sensitivity distribution. We used AC toxicity data to successfully predict toxicity of binary mixtures assuming additive toxicity. The observed time-dependent toxicity was inversely related to log K and occurred more quickly than reported previously. The results contribute to improving models for predicting oil spill impacts on American lobster larvae populations. Environ Toxicol Chem 2021;40:1379-1388. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.