Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science have found heart defects in several Gulf of Mexico fish embryos following exposure to the Deepwater Horizon oil spill.

Researchers said that the gulf populations of tunas, amberjack, swordfish, billfish, and other fishes that hatched in oiled surface habitats were largely affected.

This is the first study to examine the effects of primary toxic agents from crude oil on several commercially important ocean fish species in the Gulf of Mexico.

"This study is the first to understand the impacts of the Deepwater Horizon oil spill on the early life development of commercially important fish in the Gulf of Mexico," Daniel Benetti, UM Rosenstiel School professor of marine affairs and policy and director of the Aquaculture Program said in a press release. "The findings can be applied to fisheries management questions in marine regions where crude oil extraction is prevalent."

For the study, the researchers exposed the embryos of bluefin tuna, yellowfin tuna, and amberjack to two oil samples of which one was collected from surface skimming operations in the Gulf of Mexico and another from the source pipe at the damaged Deepwater Horizon wellhead.

The researchers found similar defects (heart development and cardiac function) in embryos when exposed to both the oil types. Among the three tested species, bluefin tuna had highest percentage of larvae with large number of defects. International Union for Conservation of Nature has listed them as endangered species.

The 2010 Deepwater Horizon disaster in the northern Gulf of Mexico is deemed the worst offshore oil spill in the history of the United States. The blast of the Deepwater Horizon well released more than four million crude oil containers into the waters during the seasonal reproduction period for commercially and ecologically important ocean fish species like bluefin, yellowfin tunas, mahi mahi, king and Spanish mackerels, greater and lesser amberjack, sailfish, blue marlin, and cobia.

"Vulnerability assessments in other ocean habitats, including the Arctic, should focus on the developing heart of resident fish species as an exceptionally sensitive and consistent indicator of crude oil impacts," said the paper's authors.

The finding is published in the journal Proceedings of the National Academy of Sciences (PNAS).