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

Abstract

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 OW ; 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 chromatographymass 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 OW 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 OW and occurred more quickly than reported previously. The results contribute to improving models for predicting oil spill impacts on American lobster larvae populations.

Changes in Temperature Alter the Toxicity of Polycyclic Aromatic Compounds to American Lobster (Homarus americanus) Larvae

“…As expected based on previous work (Philibert et al, 2021), immobilization preceded the mortality of lobster larvae. Our results point toward some increased toxicity of the tested PACs at higher temperatures, but patterns differed between the six compounds and the linear increase in toxicity with temperature predicted by the Q 10 concept was not true for all tested compounds.…”

“…Individual PACs were loaded into polydimethylsiloxane O‐rings (2.5 cm diameter, ~1.0 g each, 2.33 mm thick, product number AS568B‐210; Silicone O‐rings West) with methanol using a previously established partitioning model (Butler et al, 2016) and the methods used in our laboratory, described by Philibert et al (2021). Loaded O‐rings and 0.22‐µm filtered seawater were then added to 20‐mL scintillation vials and equilibrated on an orbital shaker for 24 h at 200 rpm at the exposure temperature prior to the introduction of the test animals.…”

Dosing Methods to Enable Cell-Based In Vitro Testing of Complex Substances: A Case Study with a PAH Mixture

“…Most comparable to this experimental set-up are studies of passive dosing via several types of polymer materials, including larger O-rings, discs, rods, or tubing of silicone or polydimethylsiloxane (PDMS) [ 21 , 24 , 25 , 30 , 36 , 37 ]. These experiments of passive dosing are most commonly applied to aquatic toxicity tests and usually are conducted on a large scale (e.g., vials or large bottles); fewer studies utilized 6- or 24-well plates, and only one study used 96-well plates [ 21 , 22 , 23 , 25 , 28 , 29 , 30 , 31 , 32 , 55 , 56 , 57 , 58 , 59 ]. Thus, our data show that while O-rings are a feasible donor on a large scale; this method is less preferred in micro-scale in vitro assays.…”

“…Solvent spiking involves direct addition of test substance diluted with a solvent of choice to the aquatic testing environment. Passive dosing involves submersion of a biocompatible polymer (e.g., O-rings) in neat test substance for absorption with subsequent transfer of the polymer and “loaded” substance into the testing environment, where equilibrium is established via passive diffusion [ 21 , 22 , 23 , 24 , 25 ]. Accommodated fractions are typically prepared by spiking neat substance into the same aquatic medium (e.g., water accommodated fraction, WAF) as the testing environment which is then stirred to stimulate compound partitioning to the WAF [ 21 , 26 ].…”

“…Several recent studies have sought to improve the dosing approaches by increasing throughput, testing compatibility with hydrophobic or very complex substances, or by applying them to mammalian cell-based assays. The use of silicone donor varieties to passively dose hydrophobic substances is the most common approach [ 21 , 22 , 23 , 24 , 25 , 28 , 29 , 30 , 31 , 32 ]. Many of these studies used polycyclic aromatic hydrocarbons (PAH) as surrogate hydrophobic compounds for understanding the toxicity of complex petroleum substances [ 33 ].…”