NOAA: Oil spill causing heart problems in Gulf tuna
Crude oil from the 2010 Deepwater Horizon disaster causes severe defects in the developing hearts of bluefin and yellowfin tunas, according to a new study by a team of National Oceanic and Atmospheric Administration (NOAA) and academic scientists.
The findings, published in the Proceedings of the National Academy of Sciences on the 25th anniversary of the Exxon Valdez oil spill, show how the largest marine oil spill in United States history may have affected tunas and other species that spawned in oiled offshore habitats in the northern Gulf of Mexico.
The study shows that crude oil exposures adversely affect heart development in Atlantic bluefin tuna and yellowfin tuna and an amberjack species by slowing the heartbeat or causing an uncoordinated rhythm, which can ultimately lead to heart failure.
“The timing and location of the spill raised immediate concerns for bluefin tuna,” said Barbara Block, Ph.D., a study coauthor and professor of biology 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.” said Block. “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.”
This mechanism explains why the team observed a range of cardiac effects in the developing hearts of intact embryos in the present study.
During the experiment, developmental abnormalities were evident in bluefin and yellowfin tunas at very low concentrations — levels below the measured PAH concentrations in many samples collected from the upper water column of the northern Gulf during the active Deepwater Horizon spill phase.
Severely affected fish with heart failure and deformed jaws are likely to have died soon after hatching. However, the NOAA team has shown in previous work that fish surviving transient crude oil exposures with only mild effects on the still-forming heart have permanent changes in heart shape that reduce swimming performance later in life.
The nature of the injury was very similar for all three pelagic predators, and similar also to the response of other marine fish previously exposed to crude oil from other geologic sources. Given this consistency, the authors suggest there may have been cardiac-related impacts on swordfish, marlin, mackerel, and other Gulf species.