The effects of weathering and chemical dispersion on Deepwater Horizon crude oil toxicity to mahi-mahi (Coryphaena hippurus) early life stages

To better understand the impact of the Deepwater Horizon (DWH,) incident on commecially and ecologically important pelagic fish species, a mahi-mahi spawning program was developed to assess the effect of embryonic exposure to DWH crude oil with particular emphasis on the effects of weathering and dispersant on the magnitude of toxicity. Acute lethality (96 h LC50) ranged from 45.8 (28.4-63.1) mu gl(-1) Sigma PAH for wellhead (source) oil to 8.8 (7.4-10.3) mu gl(-1) Sigma PAH for samples collected from the surface slick, reinforcing previous work that weathered oil is more toxic on a Sigma PAH basis. Differences in toxicity appear related to the amount of dissolved 3 ringed PAHs. The dispersant Corexit 9500 did not influence acute lethality of oil preparations. Embryonic oil exposure resulted in cardiotoxicity after 48 h, as evident from pericardial edema and reduced atrial contractility. Whereas pericardial edema appeared to correlate well with acute lethality at 96 h, atrial contractility did not. However, sub-lethal cardiotoxicity may impact long-term performance and survival. Dispersant did not affect the occurrence of pen-cardial edema; however, there was an apparent reduction in atrial contractility at 48 h of exposure. Pericardial edema at 48 h and lethality at 96 h were equally sensitive endpoints in mahi-mahi. (C) 2015 Elsevier B.V. All rights reserved.