Toxicity of the oil spilled on the Brazilian coast at different degrees of natural weathering to early life stages of the zebrafish Danio rerio.

Toxicity of water accommodated fractions (WAF) from the oil spilled on the Brazilian coast at different stages of weathering were investigated using Danio rerio. Weathering stages included emulsified oil that reached the coast (OM) and oil collected 50 days later deposited on beach sand (OS) or adhered to shore rocks (OR). Parent and alkylated naphthalenes decreased whereas phenanthrenes increased from less weathered WAF-OM to more weathered WAF-OS and WAF-OR. More weathered WAF-OS and WAF-OR were more potent inducers of zebrafish developmental delay, suggesting that parent and alkylated phenanthrenes are involved. However, less weathered WAF-OM was a more potent inducer of failure in swim-bladder inflation than more weathered WAF-OS and WAF-OR, suggesting that parent and alkylated naphthalenes are involved. Decreases in heart rates and increased heart and skeletal deformities were observed in exposed larvae. Lowest observed effect concentrations for different developmental toxicity endpoints are within environmentally relevant polycyclic aromatic hydrocarbon concentrations.