The effects of oil induced respiratory impairment on two indices of hypoxia tolerance in Atlantic croaker (Micropogonias undulatus)

The Gulf of Mexico was home to the Deepwater Horizon oil spill, and is also known to exhibit seasonal declines in oxygen availability. Oil exposure in fish is known to impact oxygen uptake through cardiac impairment, which raises questions about the additive effects of these two stressors. Here we explore this question on the Atlantic croaker using two measures of hypoxia tolerance: critical oxygen threshold (P_crit), and time to loss of equilibrium (LOE). We first demonstrated that 24 h exposure to 10.1 and 23.2 μg l⁻¹ ΣPAH₅₀ significantly impaired oxygen uptake. There was no effect of exposure on P_crit or LOE. Exposure did result in significantly different repeatability between pre- and post-exposure P_crit, suggesting that hypoxia tolerant individual may see greater impacts following exposure. These results suggest oil exposure does not have wide scale detrimental outcomes for hypoxia tolerance in fish, yet there may be fine scale impairments of ecological significance.