The Sanibel-Captiva Conservation Foundation Examines Horizon Spill 7 Years Later


On April 20, 2010, the Deepwater Horizon oil platform, the deepest well ever drilled up to that point at over a mile below the surface, exploded, causing it to gush oil onto the Gulf seabed. The result was the largest oil spill in United States History, killing 11 workers and uncountable birds and marine wildlife, while fouling roughly 575 miles of Gulf shoreline.

Before being capped 87 days later, it released approximately 206 million gallons of oil, becoming the 2nd worst in history and the most ever by accident; behind only the intentional one initiated by Iraq in the First Gulf War, resulting in the use of over 1.8 million gallons of dispersants. The spill eventually covered 65,000 square miles, from Louisiana, Mississippi, Alabama and the Florida panhandle, with a trailing edge that approached but never reached Southwest Florida.

Deepwater Horizon: Dispatches from the Gulf
Dr. Michael Parsons of FGCU discusses the aftermath of the Deepwater Horizon oil spill.

Now, almost 7 years later, the Sanibel-Captiva Conservation Foundation (SCCF) hosted the 55-minute documentary, “Deepwater Horizon: Dispatches from the Gulf,” at the Sanibel Community House last week before roughly 150 people. Following the film, Dr. Michael Parsons of Florida Gulf Coast University and Dr. Marie DeLorenzo, research toxicologist from the National Oceanic and Atmospheric Administration office in Charleston, South Carolina, presented a panel discussion and question and answer session.

Dr. Marie DeLorenzo, Dr. Michael Parsons
Dr. Marie DeLorenzo and Dr. Michael Parsons, in blue shirts, speak with audience members following the SCCF forum.

“Dispatches from the Gulf,” released in 2016 and narrated by actor Matt Damon, investigates the environmental health of the Gulf of Mexico since the Deepwater Horizon that changed the lives of thousands of communities and millions of Americans. It mobilized the largest coordinated scientific research effort around an ocean-related event in history. The documentary shares the first-hand accounts from fishermen, scientists, and activists, with the ultimate goal to learn how to cope with future spills.


Mud & Blood Cruise

One way scientists analyzed the effects is through a “Mud & Blood Cruise,” where they catch fish and drill for Gulf floor core samples on the same research ship, as it takes both to monitor changes within fish populations. There was actually on-going testing at 27 Gulf sites a decade prior to Deepwater Horizon, so scientists had a great deal of data before and after the spill for comparison. Quite a few species rebounded to pre-spill population levels, but are smaller and weigh less as a result of the oil. Collecting sea floor samples allows you to turn the pages of the Gulf of Mexico’s history backward, from hundreds of years ago to now, with the Deepwater Horizon sediments in the uppermost level.

With all that oil, scientists are hesitant to issue early declarations that this massive leak caused little or no harm, as the world’s ninth largest body of water is still under stress 7 years later, despite that tourists returned, oil drilling restarted, seafood seems safe, and charter boats are back, so what happened to that 2 million gallons? Data indicates 29% burned away the first year, mostly from the sun’s heat; 23% remains in the water and salt marshes; and 48% either dispersed or dissolved in the water, indicating that the use of dispersants, while not ideal, clearly is the lessor of two evils. Oil is still piling up in Louisiana’s salt marshes, but it is hard to find in any other identifiable places.

Good “a-ha” moments for researchers were the discovery that some microscopic organisms actually consume the tiny oil droplets and thrive, the ecosystem’s resiliency to rebound so quickly, and so far fish seem fine as long as people do not eat their gallbladders. Bad instances, however, are massive sea worm kills, dead corals, and dead sea bands of oil-eating organisms covered in brown slime with their guts full of oily residue. In deep diving, scientists confirmed their worst fears by finding lots of oil all over the Gulf floor.


Energy Versus Nature

In the end, there are no easy answers or quick fixes, especially over how much the Gulf can handle when the next major spill occurs, as oil companies are now drilling deeper and deeper, with some wells over two miles down. Energy is the prime issue of the 21st Century, as our economy is totally oil dependent, so the enormous challenge is to find the balance between energy and what nature can safely provide.

Dr. Parsons remembered “everyone was caught flat-footed by the Horizon spill, even in Southwest Florida where effects were negligible.” Researchers conducted monthly Phytoplankton data from the 1980s through 2009, leading up to the spill year, “so we have plenty of evidence to compare and contrast as a baseline. Oil actually stimulated many sample groups, but there was a big drop in Phytoplankton, meaning there is much less food to go up the chain and that becomes a big concern.”

He feels there are “good and bad things about dispersants. They can be toxic to organisms, but are better than letting the oil settle into salt marshes and mangroves and seagrasses, so we have to sacrifice something, and that is the price of damage control. Dispersants seem a far better alternative that allowing oil to roll up on our beaches, with Phytoplankton impacts appearing to be short-lived and rebounding quite fast. Florida seagrasses from the Estero Bay are healthier here because they did not have any significant oil exposure, versus Louisiana that is taking much longer to recover.”


It’s Complicated!

As to the final impact, Dr. Parson concludes, “It’s complicated! We see lingering effects in salt marches and larger fish, and still witness oil oozing up. There is probably a lot of oil on the ocean floor and we have no idea of its impacts so far, but as a society you want it there and not on the coasts. We are still learning about oil spills, to understand their results.”

Dr. DeLorenzo began her research on oil and dispersants in 2011, “to decide what to do the next time a spill occurs, as there are currently 4,000 drilling platforms and 25,000 miles of pipe in the Gulf. The use of so much widespread dispersants was unprecedented as a tool to keep oil from shorelines, so this was a positive but we still do not understand the toxicity. Where to use dispersants depends on how well they work in the environment into which we introduce them, so we will need to know more of what they will do before we apply them, such as how much does it take to cause mortality in fish, shrimp, clams, snails, crustaceans and sediment-dwelling organisms.”

She concluded, “The combination of dispersants with oil at first glance looked like it might be a type of poison that would produce a worse effect than just oil alone, but tests indicate dispersants get a bad rap, as they did their job in the Gulf. I caution, however, that each spill is unique, so we must provide responders with a battery of remedies to allow them to better act in an intelligent way. We as scientists don’t make these calls; we do the research to allow the Environmental Protection Agency, Coast Guard, and local authorities to make a more informed decision based on their own situation, so this remains very much a learning curve.”

For more information on the SCCF, call 239-472-2329, email, or see

Gary Mooney