Effects of the 2019 Brazilian Oil Spill to embryonically exposed zebrafish during early life stage development

Embryonic zebrafish (Danio rerio) were exposed to 0, 1.93, or 15.46 micrograms per liter of total polycyclic aromatic hydrocarbons (tPAHs) present from a low energy water accommodated fraction (LEWAF) of crude oil from the Brazilian oil spill in 2019. Embryos were exposed from 4 hours post fertilization (hpf) through hatching and sampled at 24, 48, 72,96, 120, 144, or 168 hpf. Zebrafish collected at 24, 48, 72, 96, 120, 144, or 168 hpf were assessed for morphological changes. Larvae collected at 96 and 168 hpf were assessed for histological changes in the thickness of retinal layers using hematoxylin and eosin staining. Larvae collected at 168 hpf were assessed for optokinetic response (OKR), a visually mediated behavioral assay that quantifies the number of eye movements while focusing on an external stimulus. The concentration of tPAHs in exposure media that embryos were exposed to were chemically validated using gas chromatography mass spectrometry.