Integrative description of changes occurring on zebrafish embryos exposed to water-soluble crude oil components and its mixture with a chemical surfactant

The effects of crude oil spills are an ongoing problem for wildlife and human health in both marine and freshwater aquatic environments. Bioassays of model organisms are a convenient way to assess the potential risks of the substances involved in oil spills. Zebrafish embryos (ZFE) are a useful to reach a fast and detailed description of the toxicity of the pollutants, including both the components of the crude oil itself and substances that are commonly used for crude oil spill mitigation (e.g. surfactants). Here, we evaluated the survival rate, as well as histological, morphological, and proteomic changes in ZFE exposed to Water Accumulated Fraction (WAF) of light crude oil and in mixture with Dioctyl Sulfosuccinate Sodium (DOSS, e.g. CEWAF: Chemically Enhanced WAF), a surfactant that is frequently used in chemical dispersant formulations. Furthermore, we compared the hydrocarbon concentration of WAF and CEWAF of the sublethal dilution. In histological, morphological, and gene expression variables, the ZFE exposed to WAF showed less changes than those exposed to CEWAF. Proteomic changes were more dramatic in ZFE exposed to WAF, with important alterations in spliceosomal and ribosomal proteins, as well as proteins related to eye and retinal photoreceptor development and heart function. We also found that the concentration of high molecular weight hydrocarbons in water was slighly higher in presence of DOSS, but the low molecular weight hydrocarbons concentration was higher in WAF. These results provide an important starting point for identifying useful crude-oil exposure biomarkers in fish species.

Automated summary

Crude oil spills have negative effects on both wildlife and human health in aquatic environments. Bioassays using model organisms are a convenient method for assessing the potential risks of oil spills. This study evaluated the survival rate, histological changes, morphological changes, and proteomic changes in zebrafish embryos exposed to water accumulated fraction of light crude oil and a surfactant commonly used in oil spill mitigation. The results showed that exposure to the surfactant mixture caused more changes compared to exposure to the crude oil alone. Proteomic changes were particularly significant in zebrafish embryos exposed to the crude oil. The study also compared the hydrocarbon concentrations in the two exposures and found differences in the molecular weight distribution. These findings provide important insights for identifying biomarkers of crude oil exposure in fish species.