Is chemically dispersed oil more toxic to Atlantic cod (Gadus morhua) larvae than mechanically dispersed oil? A transcriptional evaluation

• Published in: BMC genomics Vol. 13; no. 1; p. 702
• Main Authors: Olsvik, Pål A, Lie, Kai K, Nordtug, Trond, Hansen, Bjørn Henrik
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 14.12.2012; BioMed Central; BMC
• Subjects: Analysis; Animals; Atlantic cod larvae; Chemical; Chromatin; Cod; Crude oil; DNA replication; Embryos; Environmental aspects; Exposure; Fish; Fishes; Gadus morhua; Gadus morhua - genetics; Gene Expression Profiling; Genes; Genetic aspects; Genetic transcription; Genomics; Hydrocarbons - chemistry; Hydrocarbons - toxicity; Larva - drug effects; Larva - genetics; Larval development; Mechanical Phenomena; Natural oil dispersion; Oil spills; Oligonucleotide Array Sequence Analysis; Petroleum - toxicity; Petroleum Pollution; Polymerase Chain Reaction; Proteolysis; Repair & maintenance; Software; Survival Analysis; Time Factors; Toxicity Tests; Transcription; Transcription, Genetic - drug effects; Zebrafish; Norway
• ISSN: 1471-2164; 1471-2164
• DOI: 10.1186/1471-2164-13-702

The use of dispersants can be an effective way to deal with acute oil spills to limit environmental damage, however very little is known about whether chemically dispersed oil have the same toxic effect on marine organisms as mechanically dispersed oil. We exposed Atlantic cod larvae to chemically and mechanically dispersed oil for four days during the first-feeding stage of development, and collected larvae at 14 days post hatch for transcriptional analysis. A genome-wide microarray was used to screen for effects and to assess whether molecular responses to chemically and mechanically dispersed oil were similar, given the same exposure to oil (droplet distribution and concentration) with and without the addition of a chemical dispersant (Dasic NS). Mechanically dispersed oil induced expression changes in almost three times as many transcripts compared to chemically dispersed oil (fold change >+/-1.5). Functional analyses suggest that chemically dispersed oil affects partly different pathways than mechanically dispersed oil. By comparing the alteration in gene transcription in cod larvae exposed to the highest concentrations of either chemically or mechanically dispersed oil directly, the chemically dispersed oil affected transcription of genes involved nucleosome regulation, i.e. genes encoding proteins participating in DNA replication and chromatin formation and regulation of cell proliferation, whereas the mechanically dispersed oil most strongly affected genes encoding proteins involved in proteasome-mediated protein degradation. Cyp1a was the transcript that was most strongly affected in both exposure groups, with a 60-fold induction in the two high-exposure groups according to the RT-qPCR data, but no significant difference in transcriptional levels was observed between the two treatments. In summary, dispersants do not appear to add to the magnitude of transcriptional responses of oil compounds but rather appear to lower or modify the transcriptional effect on cod larvae.