MIAMI — Florida Keys residents may not have seen massive tar balls and fish kills after the 2010 Deepwater Horizon oil spill, but small concentrations of toxic crude were still reaching the islands and potentially harming marine life, as the extent of the deadly disaster in the Gulf of Mexico was worse than originally thought, according to a University of Miami study.

Nearly a decade after the worst offshore oil spill in U.S. history killed 11 people and dumped 200 million gallons of crude into the ocean, researchers found discrepancies in the satellite footprint that was used to establish fisheries closures and data from sampling and field tests. They concluded that the real extent of the BP oil spill may have been 30 percent larger than originally estimated. After methane seeped into the rig and triggered an explosion on April 20, 2010, oil gushed from a pipe more than 4,000 feet below the ocean’s surface for 87 days.

Looking at water and sediment measurements, oil transport models and satellite imagery, the team of researchers concluded that what appeared on the two-dimensional images provided by the National Environmental Satellite, Data and Information Service – areas that were determined to be contaminated and closed off to fishing – didn’t match what in-site data was showing.

Oil was flowing beyond the rig’s location off the coast of Louisiana toward the west, reaching the Texas shores, and to the other side toward the West Florida Shelf, the study said. It was also present in the Loop Current that carries water from the Gulf around the southern tip of Florida through the Keys and up toward Miami.

“We realized that the satellite footprint and the fisheries closure areas didn’t capture the full extent of the spill, and that the impact on marine life may have been overlooked,” said Igal Berenshtein, a postdoctoral researcher at the University of Miami Rosenstiel School of Marine and Atmospheric Science and co-author of the study. “So the second question was how toxic was this extra oil for fish and invertebrates.”

What researchers called “invisible oil” was crude in smaller and lighter concentrations that was flowing around the Gulf of Mexico, not thick enough to be detected by satellites.


Though the oil was lighter in concentration than the crude that the National Response Team was cleaning up on the surface, it was toxic because of the interaction with ultraviolet light, Berenshtein said.

“This photoinduced toxicity means that oil, even in very low concentrations, becomes more toxic than oil alone when UV light is also present,” he said.

For example, high levels of toxic chemicals called polycyclic aromatic hydrocarbons, or PAHs, released from the oil spill were found in red snappers’ livers, while researchers also observed an increase in cases of skin lesions in bottom-dwelling fish, the study said. Researchers also analyzed data showing that “fish larvae developed edema, decreased heart rates, and developmental abnormalities at low oil concentrations.”

Mike Forster, a longtime Islamorada restaurant owner who is also a backcountry angler, said he was recently speaking to lobster and crab fishermen about their slow catch this season, and he theorized it could be residual effects from the massive 2010 spill.

“No, we didn’t see the tar balls and major fish kills of any magnitude,” Forster said. “But, you can’t make believe it didn’t have an effect on the eggs, nursery of anything living in the ocean, and specifically on the Gulf side.”

That’s one of the main takeaways in the UM study, said Berenshtein. The spill happened in the deep ocean, where water is tossed around by wave action, hurricanes and storms, making it hard to estimate where oil dispersed, how much dilution it suffered, and what impact it had on marine life.


“The public and the agencies at the time believed that the satellite images accurately showed the size of spill and the water it contaminated, but we now know that there is a large component of undetected oil that can travel far and affect the fish,” he said.

Doug Rader, chief ocean scientist with the Environmental Defense Fund, monitored the spill closely and continues to investigate its legacy. He said he agrees with the study’s findings, but believes the impacts spread even farther up the East Coast, and even to Mexico and Cuba.

Rader said that when the surface oil was cleaned up and attention waned from the situation, additional toxic elements of oil not visible to satellites continued to spread at concentrations that caused harm to marine life as far as North Carolina.

“There is a complex mixture of components in oil, each of which behaves differently in the world,” Rader said.

He singled out the PAHs, which are particularly problematic because they end up settling on the ocean floor, where worms that feed off sediment eat them. Those worms end up as prey for midsized fish like snapper and grouper, which in turn are eaten by bigger fish and mammals, including humans.

“Once (PAHs) get out in the world, they stay,” Rader said.

Some environmentalists worry the spill hasn’t been fully contained.

Steve Friedman, commodore of the Florida Keys Fishing Guides Association and founding board member of the environmental group Florida Bay Forever, said that when officials dispersed the bulk of the spill and declared the emergency over, he thought the well continued to leak.

“I believe it’s been leaking for years, and is still leaking,” he said.

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