Anthropogenically sourced low concentration PAHS: In situ bioavailability to juvenile Pacific salmon

Area of Science:

• Environmental Toxicology
• Aquatic Ecology
• Biomarker Research

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are significant environmental contaminants.
• Assessing PAH exposure in aquatic ecosystems is crucial for wildlife health.
• Chinook salmon populations are facing declines, necessitating investigation into environmental stressors.

Purpose of the Study:

• To evaluate polycyclic aromatic hydrocarbon (PAH) exposure in juvenile Chinook salmon using EROD activity as a biomarker.
• To correlate PAH concentrations in water and sediment with biological responses in salmon.
• To identify sources and bioavailability of PAHs in Auke Lake.

Main Methods:

• Juvenile Chinook salmon were caged in Auke Lake, Alaska, and their gill 7-ethoxyresorufin O-deethylase (EROD) activity was measured.
• Comprehensive sampling included grab water and sediment samples, and passive sampling devices.
• PAH concentrations were analyzed, and statistical correlations with EROD activity were determined.

Main Results:

• PAHs were detected in Auke Lake at all sites except the upstream reference location.
• EROD activity in salmon significantly correlated with water pyrene concentrations (r(2)=0.9662; p=0.0004).
• Sediment samples effectively indicated PAH sources and overall contamination levels, while passive samplers reflected historical aqueous conditions.

Conclusions:

• Juvenile Chinook salmon in Auke Lake are chronically exposed to low concentrations of anthropogenically sourced PAHs.
• Waterborne PAH levels, especially pyrene, are strong predictors of biological stress in salmon.
• This chronic PAH exposure may be a contributing factor to the decline in salmon stocks.