Dispersant used to clean Deepwater Horizon spill more toxic to corals than the oil, study suggests

Dispersant used to clean Deepwater Horizon spill more toxic to corals than the oil
A coral specimen exposed to oil and dispersant displays declining health over time. The picture on the furthest right is a healthy control sample. Researchers from Temple University and Penn State University found the dispersant used to remediate the 2010 Deepwater Horizon oil spill in the Gulf of Mexico is more toxic to cold-water corals at lower concentrations than the spilled oil. Credit: Erik Cordes/Temple University

The dispersant used to remediate the 2010 Deepwater Horizon oil spill in the Gulf of Mexico is more toxic to cold-water corals than the spilled oil, according to a study conducted at Temple University. The study comes on the eve of the spill's fifth anniversary, April 20th.

In this collaborative study between researchers from Temple and the Pennsylvania State University, the researchers exposed three cold-water species from the Gulf to various concentrations of the dispersant and from the Deepwater Horizon well. They found that the dispersant is toxic to the corals at lower concentrations than the oil.

The researchers' findings, "Response of deep-water corals to oil and chemical dispersant exposure," were published online in the journal Deep-Sea Research II.

Approximately five million barrels of crude oil escaped from the well drilled by the Deepwater Horizon oil rig in 2010, and nearly seven million liters of —chemical emulsifiers used to break down the oil—were used to clean it up. Normally applied to the water's surface, the spill marked the first time that dispersants were applied at depth during an oil spill.

"Applying the dispersants at depth was a grand experiment being conducted in real-time," said Erik Cordes, associate professor of biology at Temple, who has been studying Gulf of Mexico coral communities for more than a decade. "It was a desire to immediately do something about the oil coming out of the well, but they really didn't know what was going to happen as a result."

Following the 2010 spill, Cordes and his collaborators discovered several damaged Gulf coral populations that were coated with a dark colored flocculent slime that was found to contain oil from the spill and residues from the dispersants.

"We wanted to know if the damages that had been witnessed could have been caused by the oil, the dispersant itself, or a combination of both," said Danielle DeLeo, a Temple doctoral student in Cordes' lab, who was the study's lead author. "We know that the corals in the Gulf were exposed to all of these different combinations, so we have been trying to determine the toxicity of the oil and the dispersants, and see what their impact would be on the corals."

The researchers exposed the corals to a range of concentrations for both the dispersant and the oil to determine a lethal dose for each. They were surprised to find that the lethal concentration is much lower for the dispersant, meaning it is more toxic than the oil.

"It doesn't take as much dispersant to kill a coral as it does oil," Cordes said, adding that the oil in combination with the dispersant increases the toxicity of the oil.

Using dispersants is supposed to reduce the impact of on the environment, said Cordes, "but there's increasing evidence that's not what's happening."

Cordes said that his lab will be carrying out additional studies to try to replicate the concentrations of oil and dispersant that the corals were exposed to during the Gulf oil spill, but this is the first step in determining the toxic levels of dispersants and their impact on the environment. He said their findings could assist in developing future strategies for applying dispersants at oil spills that may be more helpful than harmful to the environment.


Explore further

Oil dispersants not as harmful to marine life as predicted

Provided by Temple University
Citation: Dispersant used to clean Deepwater Horizon spill more toxic to corals than the oil, study suggests (2015, April 9) retrieved 17 September 2019 from https://phys.org/news/2015-04-dispersant-deepwater-horizon-toxic-corals.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
93 shares

Feedback to editors

User comments

Apr 09, 2015
Why is nobody in prison for this?

Apr 09, 2015
At least the dispersant is more photogenic than the oil. And that's what really matters, right?

Delay the bad effects long enough, even at the cost of worse effects later, and deal with the muted public outcry then. I swear, the societal organism has ADD.

Apr 09, 2015
How do you treat a natural "pollutant"?
Dump artificial poison on it.
Brilliant!!

Apr 09, 2015
No surprise. The planet has been dumping gigatons of raw petroleum and worse into the oceans for a half billion years.

Apr 09, 2015
Hey, Shootist timed it!

And that lets us cause another Great Extinction, . . doesn't it? Aren't we free to make choices?

Apr 09, 2015
It was a poor choice of dispersants. Someone should be sued for this, but who should receive the funds?

It's long known the toxicity of dispersants/surfactants--soaps. I was well familiar with them in the mid-90's. They should use relatively rapidly biodegraded anionic surfactants.

Or maybe they did, and it still isn't rapid enough.

How they harm is by also dispersing the lipids that the water-breathing animals need to absorb oxygen.

Apr 10, 2015
Mr shootist is broadly correct give or take being a bit over constrained of the time period. The woods hole article is very basic and simply says that we see most contemporary seeps as being the small type and that natural catastrophic trap failures have not been witnessed in recent times, give or take the Santa Barbra channel. So while the woods hold article is broadly consistent with present day observation it is inconsistent with I the subsurface record. Natural spills can be huge they are just rare.

Apr 10, 2015
Many oil field are already biodegraded which is partly why you have different api weights of oil. However shallow fields also exist with no biodegradation and deep fields exist with biodegradation there is a huge amount of variability out there. The list of caveats that go with the wh article is huge and the article thus only talks about a random general case.

A natural seep sprayed down with with dispersant is likely to be pretty much identical to the well head spill (also sprayed with dispersant) of a well drilling below the same live natural seep if you mop it up from the sea floor. Refined products are a different matter.

Leaky top seal and fault rupture are the norm in the sub surface to the extent that it is surprising that anything will trap. Fault rupture to surface is also very common and those faults can basically dump the entire content out in one go, rather than delivering it through broken pipe.

Apr 10, 2015
An interesting follow up for the investigators would be to test the impact of the dispersant in the chemo synthetic community. Seems very likely that that would be impacted?
Sadly there seems to be little love for the lower parts of the chemo synthetic food chain and micro biology is just not perceived as sexy by the main stream. People are far to stimulated by the visual pornography of macro biology.

Apr 10, 2015
From a geochemical view point they are the same. Another topic of conversation would be to talk about scale. The woods hole article is talking about seeps, which almost by definition are small compared to the underlying body of fluid. Large scale natural venting due to say fault failure would be indistinguishable from something of the scale of deep water horizon.

Offshore Norway is a good place to start to get an idea of scale of slope failures in hydrate and oil rich areas.


Apr 11, 2015
As a baseline we should be hearing about what the run-off from nitrate fertilizers used to farm sugar cane are doing to the environment. It's mega-hypocrisy, all the vegan and anti-cruelty vegetarians, addicted to sugar (who also own cars!), that think it's all down to THEM to change, that all environmental destruction comes from business interests. Whilst breeding like rabbits.

The environment would be in fine shape if "environmentalists" cared 1/2 as much for the environment as they do their ego identity as environmentalists!

Apr 11, 2015
Dispersant used to clean Deepwater Horizon spill more toxic to corals than the oil, study suggests

...and why am I not surprised by this?

Apr 11, 2015
Dispersant used to clean Deepwater Horizon spill more toxic to corals than the oil, study suggests

...and why am I not surprised by this?

And they should be greatly neutralized in the process of doing their jobs as well... Biodegradable surfactants... I am guessing whom ever chose them looked for a quick solution, and didn't research what had already been known.

Simply put there are those that are biodegradable, and those that take too long.

Apr 11, 2015
But they are not the same. Stop obfuscating. If they were the same - we would need to spend billions of dollars cleaning up the seeps - or else suffer the kind of environmental damage we observed from Exxon Valdiz etc.


Apologies if that sounds like obfuscation but one way of looking at the question is from a geochemical stand point. Your point appears to more the scale of the disaster.

So to address the scale issue, we need to add some new vocabulary. Seeps are generally a small form of secondary migration (remigration). Secondary migration can be sudden, as in trap rupture, or it can be slow, like little burps. If the fault ruptures to surface, hydrocarbons can migrate direct to surface along the whole open part of the fault.
With that concept in mind take a map of the world and overlay it with a map of large earthquakes and another map of oil and gas fields. Finally consider 5 years after DWH where is all the oil?

Apr 11, 2015
What surprises me is why people like "shootist" can't be banned from forums like this.

Last I checked, many scientist are/were people who cared about *things*. Sometimes they even cared about *things* other than money and worked years of their lives to improve *things*.

Sometimes, people in general, aren't slavish whores to the petro-dollar, unlike sheeple-shootists and the ilk.

Is "shootist" even a person or is it just some sock-puppet for an Italian-style fascist cult or stinktank?

Apr 11, 2015
The probability of a trap failure is actually quite high, but fortunately for us those seismically active areas tend to be quite leaky anyway so giant fields tend not to accumulate but 5 million barrels is pretty small for a field. As for the frequency of these events...well there a topic you can do your PhD on.

One thing to keep in mind from a biodegradation standpoint: Generally the only thing you have left in nature are the things which are tough to digest, which in the case of oil is mainly resins and asphaltenes. Raw oil and condensate is incredibly variable liquid chemically. The % proportion of resins and asphaltenes from any particular source also vary widely, the average is pretty low but the range large, so the amount of residual you see after biodegradation will vary enormously, depending on where you are in the world and what the source rock - migration- secondary migration pathways were.

Apr 12, 2015
Personally I don't eat anything from the Gulf of Mexico any more. Maybe in 20 or 30 years it will be safe to eat again.

At least they didn't add poison to the oil in the Valdez disaster.

Another point about the Horizon disaster: the oil company execs were the ones who made the fateful decision that caused it. Because they were being cheap and greedy, and ignoring the experts who told them cheap and greedy is risky.

Apr 12, 2015
Oh, and BTW those same execs were told not to use the dispersant in that manner: http://ioscprocee...7-1-1007

That is by *Exxon's own pet scientists*, and was published in 1997. As usual, oil company execs ignoring scientists, this time their own scientists. Dumb da dumb dumb.

Apr 12, 2015
1. How many here have experience in the oil drilling industry?
2. How many here know anything about that particular dispersant?
3. How many are expert in oceanic bacteria?

Ok, those of you who actually know what you're talking about, please carry on.

Apr 12, 2015
1. How many here have experience in the oil drilling industry?
Appeal to false authority detected.

Apr 12, 2015
ab3a
1.Not much to know coming out of the drilling industry. Now refining and application industry has good knowledge.
2.Do they name the dispersant? If you gave me what it was I can tell you plenty, however, they probably used a non-ionic surfactant. Powerful, but many don't break down.
3. Not me. But the mechanism by which fish die due to dispersants is familiar to me.

Apr 13, 2015

"There is an oil spill everyday at Coal Oil Point (COP), the natural seeps off Santa Barbara, California, where 20-25 tons of oil have leaked from the seafloor each day for the last several hundred thousand years.

"Earlier research by Reddy and Valentine at the site found that microbes were capable of degrading a significant portion of the oil molecules as they traveled from the reservoir to the ocean bottom and that once the oil floated to sea surface, about 10 percent of the molecules evaporated within minutes."

Apr 13, 2015
"The amount of natural crude-oil seepage is currently estimated to be 600,000 metric tons per year, with a range of uncertainty of 200,000 to 2,000,000 metric tons per year. Thus, natural oil seeps may be the single most important source of oil that enters the ocean"

-The problem isn't the material, it's the fact that it's spilled into environments that haven't adapted to it. But since species have evolved in the presence of petroleum, systems can recover quickly, which is the case in the gulf.

Apr 13, 2015
I guess otto did not see the oil from the BP Blowout (not a spill) did not get eaten by his bugs, nor did it all evaporate.

And years later, it has not recovered.

Meanwhile, we had a solar blowout of our own here yesterday, reaching about 80 degrees, but the wind spill made it wonderful.

Apr 13, 2015
otto is correct about the oil-eating petrophages, or whatever, and if he is interested, former columnist Art Hoppe had a good comment on it a couple of decades ago in the SF Chron.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more