Evaluation of Gene Bioindicators in the Liver and Caudal Fin of Juvenile Pacific Coho Salmon in Response to Low Sulfur Marine Diesel Seawater-Accommodated Fraction Exposure

Low sulfur marine diesel (LSMD) is
frequently involved in coastal
spills and monitoring ecosystem damage, and the effectiveness of cleanup
methods remains a challenge. The present study investigates the concentration
and composition of polycyclic aromatic hydrocarbons (PAHs) dispersed
in LSMD seawater accommodated fractions (WAFs) and assesses the effects
of exposure on juvenile coho salmon (Onchorhynchus kisutch). Three WAFs were prepared with 333, 1067, and 3333 mg/L LSMD. The
sum of 50 common PAHs and alkylated PAHs (tPAH50) measured by gas
chromatography/triple quadrupole mass spectrometry showed saturation
at ∼90 mg/L for all WAFs. These WAFs were diluted 30% for 96
h fish exposures. qPCR was performed on liver and caudal fin from
the same genotypically sexed individuals to evaluate PAH exposure,
general and oxidative stress, estrogenic activity, and defense against
metals. Excluding metal response, our analyses reveal significant
changes in gene expression following WAF exposure on juvenile salmon
with differential sensitivity between males and females. The 3-methylcholanthrene
responsive cytochrome P450-1a (cyp1a) transcript
exhibited the greatest increase in transcript abundance in the caudal
fin (10–18-fold) and liver (6–10-fold). This demonstrates
that cyp1a is a robust, sex-independent bioindicator
of oil exposure in caudal fin, a tissue that is amenable to nonlethal
sampling.