Deepwater Horizon oil spill
March 26, 2014

Heart Abnormalities Found In Fish Embryos Affected By Deepwater Horizon Oil Spill

redOrbit Staff & Wire Reports - Your Universe Online

Crude oil from the 2010 Deepwater Horizon disaster has been causing heart abnormalities in some large marine fish, according to research appearing Tuesday in the journal Proceedings of the National Academy of Science.

In the study, researchers from the US National Oceanic and Atmospheric Administration (NOAA) and colleagues from American and Australian universities say the 200 million gallons of petroleum that spilled into the Gulf of Mexico during the incident has caused severe defects in the developing hearts of tuna embryos.

The incident, which occurred between April and July 2010, “coincided with the spawning window for commercially and ecologically important species” including the yellowfin tuna and the Atlantic bluefin tuna – the latter of which is already one of the most threatened fish in the world, according to Louis Sahagun of the Los Angeles Times.

According to the University of the Miami, one of the institutions involved in the research, the study is the first to analyze the impact that toxic agents known as polycyclic aromatic hydrocarbons (PAHs), which are released from crude oil, could have on pelagic fish species in the Gulf of Mexico. The authors determined that “losses of early life stages” were “likely” for Gulf several types of large predatory fish spawned in oiled surface habitats.

The NOAA investigators and their colleagues found that bluefin tuna, yellowfin tuna and amberjack embryos which were exposed to Deepwater Horizon oil samples collected in the field developed defects in cardiovascular development. Those defects occurred in PAH concentrations of between one and 15 parts per billion and resulted in irregular heartbeat, circulatory disruption and pericardial fluid accumulation, Sahagun said.

The PAH concentration of those samples were actually lower than those measured in samples collected from the upper water column of the northern Gulf of Mexico during the spill, he added. One of the two different oil samples that the embryos were exposed to originated from the surface skimming operations in the Gulf of Mexico, while the other came from the source pipe attached to the damaged Deepwater Horizon wellhead.

“The timing and location of the spill raised immediate concerns for bluefin tuna,” explained Dr. Barbara Block, a co-author of the study and a biology professor at Stanford University. “This spill occurred in prime bluefin spawning habitats, and the new evidence indicates a compromising effect of oil on the physiology and morphology of bluefin embryos and larvae.”

“We now have a better understanding why crude oil is toxic, and it doesn't bode well for bluefin or yellowfin embryos floating in oiled habitats,” she added. “At the level of a single heart muscle cell, we've found that petroleum acts like a pharmacological drug by blocking key processes that are critical for cardiac cell excitability.”

NOAA research toxicologist Dr. John Incardona, the lead author of the study, told the Times that larvae that had been exposed to high levels of PAH were “dead within a week, but we still don’t know how long they lived after exposure to lower levels, or how much spawning area may have been impacted.” However, a BP spokesperson countered that the paper “provides no evidence to suggest a population-level impact on tuna, amberjack or other pelagic fish species in the Gulf of Mexico.”

Image 2 (below): This image shows a normal yellowfin tuna larva not long after hatching (top), and a larva exposed to Deepwater Horizon crude oil during embryonic development (bottom). The oil-exposed larva shows a suite of morphological abnormalities including fluid accumulation from heart failure and poor growth of fins and eyes. Credit: NOAA