Evaluating Embryonic Exposure of a Field-Weathered Crude Oil on Early Life Stage Toxicity of Atlantic Cod ( <i>Gadus morhua</i> ) Using the PETROTOX Model

Early life stages (ELS) of marine fish are sensitive to oil exposure; however, due to chemical complexity, estimating environmental risks of crude oil spills on spawning products is challenging. In this study, we applied a modeling approach to estimate the sensitivity of Atlantic cod (Gadus morhua) embryos to dissolved crude oil components. High-resolution GC × GC analysis was used to characterize the crude oil composition and allocate its constituents into hydrocarbon blocks (HCB) covering 16 chemical classes across carbon numbers. These data were used as input to the PETROTOX model, which integrates a solubility model with the target lipid model (TLM) to predict toxicity based on dissolved hydrocarbons. Cod embryos were exposed to environmentally relevant concentrations of dissolved hydrocarbons during a critical 4 day window, followed by recovery in clean water until 3 days post hatch. Sublethal effects, including larval deformations and cardiotoxicity, were quantified, and end point-specific critical target lipid body burdens (CTLBBs) were derived by fitting TLM predictions to observed toxicity using calculated toxic units (TU) from modeled dissolved concentrations. Estimated CTLBB (6.6–18.2 μmol/g octanol, confidence intervals 4.9–22.9) confirm the high sensitivity of marine fish ELS and demonstrate that dissolved oil components not captured by routine targeted (gas chromatography–mass spectrometry (GC-MS)) analyses contribute substantially to overall toxicity.