The Gulf Oil Spill and its Ecological Impact


Prosanta Chakrabarty is a fish zoologist at Louisiana State University in Baton Rouge and the curator of ichthyology (fish zoology) at The LSU Museum of Natural Science.

The native of Bayside, Queens earned a B.Sc. in applied zoology at McGill University, then completed a Ph.D. in Evolutionary Biology at the University of Michigan.


He and a few colleagues recently discovered two new  species of pancake batfish in the Gulf of Mexico. Since the Gulf is the only known habitat of these species, ironically these two species of pancake batfish may be in danger of becoming extinct before they are even considered for the annals of fish biology, since their only known habitat is now endangered by the Gulf oil spill.

Regarding the oil spill, some people are still saying that the underwater plumes do not exist, right?

The only people denying the existence of the underwater plumes are the people at BP. And they offer no evidence to contradict the extremely solid evidence provided by four universities, including LSU, of the existence of these huge underwater plumes of oil.

Not only is there a great deal of empirical evidence of these underwater oil plumes, but also these plumes are exactly what you’d expect when you spray dispersants in the deep sea.

When oil and water mix, the oil rises to the top. This is because the specific gravity, or relative density, of oil is lower than that of water. This is true for both freshwater and slightly denser saltwater.

The dispersant works as follows: The oil mixes with the dispersant and forms into tiny microdroplets of oil. These microdroplets have the same specific gravity as the water, so they just kind of hang suspended in the water. On the surface, this helps to break up the oil.

But in the deep sea, this prevents the oil from rising to the surface as quickly. The oil just hangs suspended in the depths, and is moved by the deep-sea currents.

In the history of oil spills before this one, dispersants had only been used on the surface. So this is the first time ever that dispersants have been used subsurface.

You also have to consider that in the deep sea there are hundreds of pounds of pressure per square inch; and it’s very cold, maybe one or two degrees Celsius; and there’s no sunlight to break down the dispersants—there is no sunlight below about 1,000 meters. All of those factors mean even more that the oil down there, when mixed with dispersant, will not rise to the surface for a long time.

Unfortunately we can’t measure the true impact of the spill if most of the oil is below the surface.

Are you saying that if the dispersants had not been applied at the well-head, then most or all of the oil would rise to the surface and these underwater plumes would basically not exist?

For the most part, yes. Or at least, the underwater plumes would be far shorter-lived since they would be rising to the surface.

If we had avoided the deep sea use of dispersants, and had simply let all of the oil rise to the surface or just below the surface, the situation would be much less catastrophic: We know how to deal with oil at the surface. We have precedent for that: We can skim it, we can burn it.

On the other hand, we cannot treat oil in the depths of the sea. There is no precedent. We don’t know how to do it. And as of now there is no plan to even try.

The trade-off was made between two fragile habitats: the marsh/freshwater habitat, and the deep-sea habitat of the Gulf of Mexico.

The marsh/freshwater habitat on the coast is very visible to the public, and of course a disaster there is also a PR disaster for the company that caused it.

The deep-sea habitat is largely unknown and certainly unseen. So in a sense, it is out of sight, out of mind. BP attempted to save the marsh/freshwater habitat at the expense of the deep-sea habitat.

But even with use of dispersants at the well-head, still a lot of oil is rising to the surface and is now making its way into the marsh/freshwater habitat—hence all the oil-covered fish, birds, and other creatures that are making the news.

So, instead of one habitat being saved at the expense of the other, effectively both habitats have been ruined.

Let’s talk about your recent discovery: What does the pancake batfish look like?

It does not look anything like a normal fish.

The pancake batfish is horizontally flat, like a spiky pancake. Its mouth is a little horizontal slit on the front. Its eyes are relatively large and just above the mouth.

The fins are bent in such a way that they are used basically like little legs to help the fish hop along the sea-floor, where it spends most of its time. The pancake batfish eats small invertebrates that make it down to the benthic level (ocean floor).

Pancake batfish are not uncommon in the Gulf but we are still learning about abundance records for the two new species. Scientists haven’t been keeping track because they didn’t know they existed. One of the new species has a very limited range and I’ve only seen a handful of them, and that was before the spill. I’m concerned that this species may be greatly impacted.

How did you and your colleagues discover these two new species?

There are pancake batfishes around the world. And there was one species that was known in the Gulf, named Halieutichthys aculeatus.

We were looking through some jars of batfish (at the American Museum of Natural History in New York City) and noticed some variation, in terms of color patterns and patterns of tubercles, as well as body size. And we thought that these variations may correspond to a new species of the fish—possibly two other species.

After I moved to Louisiana, we went out onto the Gulf and we collected some fresh specimens and found that in fact the variation was real—it was not some artifact of preservation—so we described the two new species. So now there are three known species of pancake batfish in the Gulf, rather than just one. And as far as we know, the two newly discovered species may exist only in the Gulf.

Unfortunately there appears to be a risk that these newly discovered species of pancake batfish may be endangered.

I understand that many fish are spawning now. How would this spawning be affected by the oil spill?

Most famously, the fish that is spawning right now is the Bluefin tuna, which is the most expensive fish in the world—one large Bluefin tuna can be sold for more than $100,000. There are also many other fishes spawning now including the black tip shark, the scalloped hammerhead, two marine catfish species, the gulf toadfish, cobia, dolphin fish, Spanish mackerel, some sailfish, red snapper etc.

So all of these eggs and larvae are being produced, and these are very fragile, so their likelihood of surviving being inundated with oil is very small. Potentially, basically whole generations of these fish species could be lost.

The deep-sea environment of the Gulf is very poorly known. There are very likely numerous undiscovered species of flora and fauna there, and there are many species about which we know almost nothing.

It was a terrible choice—and unprecedented in human history—to cause oil to be maintained at this subsurface level, where we do not know its impact. Just because we cannot see it or understand its impact at these depths, does not mean that it is not doing tremendous—and quite possibly irreversible—damage.

How does the Gulf oil spill compare with that of the Exxon Valdez?

These two oil spills are very different. The Exxon Valdez was a tanker that spilled crude at the surface. And that crude stayed at the surface, and then hit the beaches quickly. We understand how to deal this kind of problem.

But the Gulf of Mexico spill is occurring hundreds of meters below the surface. As I said earlier, we don’t know how to deal with it, and we don’t know much about what its impact will be. So the two are really not comparable.

What are the prospects for eventual recovery of the environment?

I do think that it will recover.06d7e1f31f8f6dcd7873d8b24ac71c2a-3

Do you have any opinion about how long it might take?

This situation is unprecedented, and there is so much that we do not know, that I would not want to speculate.

Well, do you think that we are talking about something on the order of, say 10 years, or 100 years?
I don’t think we’ll be seeing oiled birds this time next year. I think that also the surface oil will be dealt with within something close to that time frame.

It would be very interesting to know how long the oil/dispersant mix will last underwater. There’s no way to guess.

What can the average person do to help this situation?

There is no shortage of people who want to volunteer. But they are being held back because of the required training. Sadly, you must now go through hazmat training just to get out to the Gulf. I think in terms of actual hands-on clean-up, leave that to the professionals.

In terms of funding, hopefully BP and secondarily the federal government will be able to help out. If money is donated it should be sent to the people most affected—the fishermen and the local businesses. Come to Louisiana, to the Gulf, support those businesses. The viewpoint that the Gulf is doomed is false and is unfortunate.  The Gulf will rebound, and the best thing that people in other states can do is support the Gulf is to come here.

And what should people communicate to their elected representatives?

We must communicate to them that we want them to take actions to ensure that this never happens again. To use a cliché that is apt here: We must be proactive rather than reactive.

We must require off-shore oil rigs to drill relief-wells at the same time that they build oil wells. If that had happened here, then at least the leak itself could have been stopped very quickly.

We must, finally, think seriously about the consequences of depending on oil, and we must invest much more heavily in clean energy. How about an electric car on every driveway, and solar power on every roof?

We must not allow the use of dispersants below the surface again unless and until we have studied and understood how the dispersants break down oil in the deep sea, and how particular microbes can break down the oil/dispersant mix. Armed with that information, we can make more informed decisions about where rigs should be allowed and where they should not.

It is time to face this fact: Our leniency toward oil companies has grave consequences for the environment.

Ranjit Souri lives in Chicago.

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