A disturbing finding on the effects of oil spill was announced on Monday, as the 4-year commemoration of the BP Deepwater Horizon spill approaches. A recent study found that polycyclic aromatic hydrocarbons (PAHs)—known to be associated with cancers—generated from the oil spill caused heart defects in commercially important tuna and amberjack.
Led by the National Oceanic and Atmospheric Administration (NOAA), the study focused on important spawning and rearing sites in the northern Gulf of Mexico. The timing of the spill coincided with the spawning season for several species of fish, including bluefin and yellowfin tunas, mahi mahi, amberjack, and king and Spanish mackerels. Each of these species plays an important ecological and economic role in the Gulf.
The NOAA study concentrated on the effects of oil spill on tunas and amberjack development. Researchers re-created the conditions of the spill in the lab, exposing tuna and amberjack embryos to crude oil-derived PAHs. After exposure, scientists observed “a slowing of their heartbeats,” said Barbara Block, a co-author of the study. Embryos are highly sensitive to their surroundings, and early life-stage exposures to PAHs cause severe defects in heart development. Collective effects of PAHs during early developmental stages can damage the structure and function of the adult fish heart, resulting in reduced cardiac performance.
Consistent with this finding, a 2010 study on pink salmon following the Exxon Valdez spill found that exposures to crude oil, even at very low levels, during early life developmental stages reduced survival to adulthood by 40 percent.
Tuna and amberjack spawn in the northern Gulf of Mexico where the oil slicks accumulated. Their buoyant eggs remain at the surface, where water was saturated in crude oil-derived PAHs. Tuna and amberjack are fast-swimming marine predators that depend on their cardiac function to hunt for food. Any damages to their heart development severely limits their ability to hunt and can cause noticeable population declines. This decline is especially alarming for the fishing and environmental communities in the Gulf of Mexico, especially considering that the bluefin tuna stock has been declining since the 1960s and all implemented management measures have not rebuilt their population.
“For a species like bluefin tuna, BP’s oil was a shot to the heart,” says Jacqueline Savitz, Oceana vice president for U.S. oceans.