Application of Flow Cytometry to Assess Deepwater Horizon Oil Toxicity on the Eastern OysterCrassostrea virginicaSpermatozoa

Abstract

The Deepwater Horizon (DWH) oil spill in 2010 resulted in the release of millions of liters of oil into the Gulf of Mexico. Dispersants such as Corexit 9500A were used to disperse oil both at the well-head and at the surface. Polycyclic aromatic hydrocarbons and dispersants have been shown to deleteriously affect early life stages of organisms including oysters. This study examined the impacts of chemically enhanced water-accommodated fractions [CEWAF; 1.29–26.14 µg/l tPAH50 (a sum of 50 different polycyclic aromatic hydrocarbons)], high-energy water-accommodated fractions (HEWAF; 16.53–248.89 µg/l tPAH50), and dispersants (0.625–10 mg/l) on the cellular functions (viability, mitochondrial membrane potential (MMP), reactive oxygen species production (ROS), and acrosomal integrity) and resulting fertilization success of eastern oyster Crassostrea virginica spermatozoa. While viability of spermatozoa was not affected by CEWAF and HEWAF at concentrations tested, dispersant exposure caused significant decrease in viability at the highest concentration tested. Fertilization success as well as MMP and ROS production were significantly decreased upon exposure to CEWAF, HEWAF, and dispersants. Also, although not affected by HEWAF exposure, acrosomal integrity decreased upon exposure to CEWAF and dispersants at concentrations tested. The results of this study suggest that impaired fertilization and reduced viability observed after exposure to DWH oil spill contaminants may result, at least partially, from alterations of cellular functions of spermatozoa and contribute to negative effects on oyster populations, and thus the ecology and economy of the Gulf of Mexico.