>>NARRATOR: On April 20, 2010, the "Deepwater Horizon" rig

exploded in the Gulf of Mexico, killing 11 workers

and setting off the largest accidental marine oil spill

in the history of the petroleum industry.

>>We haven't had an oil spill of this magnitude at this depth

and in this environment.

>>This was a systematic failure on the part of BP,

the industry in general,

and of the government regulatory regime.

>>NARRATOR: Over the course of nearly three months,

roughly 4.9 million barrels of South Louisiana crude

gushed out of the Macondo well and into the Gulf of Mexico.

>>It was beyond my worst fears.

It was something I hope I never see again.

>>NARRATOR: The Macondo wellhead was located

at 5,000 feet beneath the water's surface,

discharging large amounts of oil and gas

under enormous pressure.

>>Most other spills are associated with a surface breach

from a tanker.

The oil sits on top of the water.

This was a completely different situation.

This was the first deepwater blowout.

>>NARRATOR: 2.9 million gallons

of the chemical dispersant Corexit

were applied at the surface and near the wellhead

to break up the oil and keep it from soiling sensitive marshes.

>>Dispersants were a novel concept

in terms of using them subsurface.

There's a great amount of angst, not only in the public,

but among the federal agencies-- what are the limits of this?

Is this a good or bad thing?

>>I don't think anybody knows what the answer to that is.

I understand why the heads of agencies made the decision

to use the Corexit.

They were trying to avert a worsening condition

on the seashore,

in the sensitive nursery areas and the estuaries.

By making that decision,

they made the conditions worse offshore and at depth.

It was a no-win situation.

>>Trying to understand the balance

of those pluses and minuses in the long term

is clearly something that we have to find out.

>>NARRATOR: Opinions on the fate of the oil vary widely.

It is estimated that anywhere between 13% to 60% of the oil

remains in the Gulf of Mexico,

potentially affecting ecosystem health for years to come.

What will the long-term impacts be?

How long until the true extent of this disaster will be known?

>>Major funding for this program

was provided by the Batchelor Foundation,

encouraging people to preserve and protect

America's underwater resources.

>>NARRATOR: The catastrophic oil spill in the Gulf of Mexico

may no longer make headline news...

...but the response to the disaster is far from over.

Scientists from the government, academia,

and independent research institutions

continue to study the impact of the spill.

Among them is the faculty of the College of Marine Science

at the University of South Florida,

who became involved early on.

>>We had research vessels sitting at the dock.

We had personnel that had expertise in various areas

related to the spill, and so we felt that we needed to react.

>>NARRATOR: The USF College of Marine Science,

located in St. Petersburg, Florida, is the home base

for the Florida Institute of Oceanography's

research vessel Weatherbird II.

>>We were among the first vessels that were directly

in the oil spill, and we worked closely

with the federal government and with the state.

And we did it for several reasons, because, you know,

we felt like it was our responsibility.

We are a public institution.

We are here to serve the citizens of Florida,

and there was tremendous concern about what this will do

to our economy, to our tourism, which has been a big issue.

>>NARRATOR: Prior to the Weatherbird's

first research cruise in May of 2010,

a group of local researchers and faculty members

at the College of Marine Science

gathered to come up with a strategy.

>>We had a long discussion

about what would be the optimum sampling plan.

>>We had a couple of reasons

for expecting there to be a subsurface layer of oil.

One is some experimentation that was done

that indicated the majority of the oil released at depth,

at tremendous pressure, will not make it to the surface.

The pure physics of having very small droplets of oil--

which form naturally,

but they're also created intentionally

by dispersants such as Corexit--

those oil droplets have a very hard time

fighting against the resistance of the water on their way up,

and they end up being stationary.

>>NARRATOR: The USF scientists also knew

that shortly after the spill, a different group of researchers

working from the research vessel "Pelican"

had discovered an undersea hydrocarbon plume

to the southwest of the "Deepwater Horizon" drill site.

>>And that clicked for us,

especially with our circulation models that suggested

both a trajectory to the southwest,

but also to the northeast in the direction

of the continental slope and shelf of Florida.

>>So that narrowed things down very much,

to the point where we could look at the charts

and pick a place and say,

"This is likely to have oil at it."

We also picked areas that we thought would not have oil

for comparison.

>>We wanted to cover areas

that were of more intrinsic importance

to the state of Florida, as well as to cover regions

that other investigators weren't covering.

>>So we had a number of stations selected

at different distances from the wellhead

at different depths that were designed

to intercept any unseen oil moving toward the state.

>>NARRATOR: Once at sea,

it didn't take the researchers very long

to find subsurface oil.

>>Finding it, we thought, might be like a needle in a haystack.

But we found the oil within a few days.

>>It was a thick plume.

We were able to recognize two components--

one was at 400 meters that spanned about 100 feet thick,

and the other one was located

between 1,000 and 1,200 meters water depth,

which was essentially the bigger plume,

and that extended for upwards of 600 feet.

We were able to see these features in the subsurface

simply using a fish finder.

>>NARRATOR: Once back in the lab, Dr. Hollander and his team

ran chemical tests to confirm the plume was made up of oil.

Next, they matched, or fingerprinted, the plume

to the oil released by the ill-fated Macondo wellhead.

And the research didn't end there.

Since May of 2010,

the scientists have made repeated trips to the area.

While at sea, experts use a number of instruments

to collect data that might provide clues

on the environmental impacts of the oil spill.

Water samples are collected

using a device called a Rosette sampler.

>>A Rosette sampler has various bottles

that we can trigger at different depths.

And the way we decide what depths to trigger at is based

on sensors which are attached to the Rosette Sampler.

There's sensors for fluorescence, temperature,

depth, and also light-scatter,

and the light-scatter is a crude indication

of where there might be oil droplets.

>>The data from the sensors is retrieved back

through an electronic cable so that, on the ship,

we can see the data in real time.

>>NARRATOR: The scientists collect water samples

at standard depths, as well as in areas

where they observe some unusual features.

>>All right, could you bring her up to 800?

>>NARRATOR: The water samples collected are then used

for various analyses.

One technique can quickly detect the presence of hydrocarbons

in the water.

>>The technique is based on the fluorescence properties

of some chemical compounds.

What we do is we shine light of different energies on a sample,

and we collect all the emission at different wavelengths.

This gives us a three-dimensional picture

of the total fluorescence of the water in our sample.

>>So at this characteristic level here,

which is in the ultraviolet range

that's still below the detection level of the human eye,

that's a telltale sign of a petroleum signature

in the water.

>>NARRATOR: Samples that test positive

for hydrocarbon presence

are analyzed further and fingerprinted

to see if they are from the "Deepwater Horizon" spill site.

Other USF researchers along on the cruises

analyze water samples from the same sites

to see if they detect toxicity.

To do so, they use two different tests, or assays.

>>So for this assay, we are using a living organism,

a type of phytoplankton called dinoflagellate, as an indicator

whether or not there is something harmful in the water,

something that will negatively affect its metabolism.

So these dinoflagellates bioluminesce, or they glow,

and produce light as part of their natural metabolism.

And when they are stressed,

they will produce a lower level of light.

If there is a decreased light emitted,

there is something present in the environment

that is making them unhappy,

whether it be hydrocarbons or something else.

Essentially, we are looking for a correlation

between the toxicity data we've come up with

and data collected by scientists

that shows the presence of hydrocarbons.

So if we can correlate toxicity

with the presence of hydrocarbons,

that would provide evidence

for a biological effect in the environment.

>>NARRATOR: The second test, or assay, uses a bacterium

instead of phytoplankton to search for toxicity.

>>No one organism reacts to all the toxicants.

What we found was that the bacterial assay

was more sensitive to oil.

The dinoflagellate assay was more sensitive to the Corexit.

>>NARRATOR: These tests show,

if there is an acute toxicity present,

that could have an immediate impact on the ecosystem.

Scientists are also very concerned about the impact

that low-level, long-term exposure could have

on marine species and ecosystem health.

>>The chronic toxicity, the sub-acute toxicity

we haven't measured,

and we don't know what the impact of that's going to be

on the food chain, on fisheries,

and the health of the Gulf of Mexico.

>>The analogy is you can stick your nose into a bucket of paint

and you can sniff for a minute and get a headache,

a raging headache,

or you can paint your room and sleep in the room overnight

and wake up with the same headache.

So you can have a lower concentration

in the surrounding environment

but be exposed to it for a longer period of time,

giving the same toxic response.

>>NARRATOR: Another toxicity assay

looks at the potential of toxins to cause DNA mutations.

Of the water samples collected in August 2010,

about half were genetically toxic.

Tests conducted as recently as February 2011

continued to find genetically toxic samples.

>>And that means mutagenic,

or the capability to damage DNA and cause mutations,

and mutations can lead to cancer

and other bad effects in marine life.

And the other thing about DNA-damaging agents is that

it becomes a heritable trait.

If there's a mutation that's caused,

it can be permanently changed

in that particular breed stock or organism,

so we're very concerned about those types of toxicities.

One of the most susceptible to genetic toxic materials

are larvae.

And these are organisms that are just rapidly growing,

rapidly dividing, synthesizing a lot of DNA.

Now, the problem is that

the larvae won't turn up to be adult fish

for maybe three or four years,

so we might not really see the genetic impact

for a couple years,

and this might manifest itself in any number of features.

>>NARRATOR: Another group of USF scientists

is focusing their research on the impact the spill is having

on the bottom of the food chain.

>>The part of the food web that our group is targeting

is the lower end of the food web,

which includes the small microscopic plants and animals.

>>NARRATOR: Those microscopic plants and animals

are known as plankton.

>>Which means small organisms adrift with current.

Phytoplankton are the microscopic plants

that are unicellular plant life.

The zooplankton are the small, microscopic animals.

They range in size from microscopic,

which are the same size as the plants,

to individuals like small fish larvae, for example,

that you can see with the naked eye.

And we do a variety of different analyses

to determine what the composition is

of the phytoplankton and micro-zooplankton,

how many are there,

and how that changes through time.

And so what we're trying to observe is any differences

from a normal, natural variability.

>>NARRATOR: Observing such potential changes

is a bit of a challenge for scientists.

>>The Gulf of Mexico has been understudied,

so we didn't have really good baselines for comparison.

>>It's a very complicated system.

I always say the Gulf of Mexico

used to be the Rodney Dangerfield of oceans--

it never got any respect.

>>We need a lot more attention paid to establishing

these baselines of all types so we know what normal is.

>>If we had had years of data to this point where we knew

what the natural variability was over space and between,

you know, week to week, month to month, year to year,

we would be able to determine much more accurately

what the effects of the BP oil spill were.

>>NARRATOR: Despite some of the uncertainties,

scientists say they have observed a change

in the abundance and health of plankton,

and they expect to see continued changes over the next few years.

An increased mortality of plankton

could have serious implications for the entire food web.

>>We all fear what we call regime shifts,

when you have a large-scale change

in the dominant animals of your ecosystem.

It's very stubborn-- once it switches over to this new order,

it doesn't go back.

And so that would affect fishermen and cultures

all around the Gulf of Mexico

if all of a sudden a certain species of animal

that's been harvested for generations

has been replaced by another one.

>>I'm very concerned about things like

Atlantic bluefin tuna,

which a large fraction of the stock spawns in the area

where there was oil in the water.

>>And so that's a depleted stock as it is,

and so any factor that might reduce the number of animals

that might recruit to the population is of concern.

One of the things that's kind of a truism

of these big environmental events like oil spills is that

we need to expect the unexpected,

that there may, in fact, be these sub-lethal effects

that will only reveal themselves over time.

And we certainly saw that with "Exxon Valdez,"

and it's very likely that we'll see that here.

>>In the case of the "Exxon Valdez," four years went by

and the local herring stock was reopened for fishing,

and there was an immediate collapse in that fishery,

and that stock has not recovered since, and decades have passed.

>>NARRATOR: To determine the impact

the Gulf oil spill is having on fish stocks,

USF researchers are using an innovative method.

>>We're looking at the chemistry of otoliths.

Otoliths are ear bones that occur in the fish's head.

They're laid down in layers like an onion or tree rings,

and they incorporate the chemistry

of the water around them.

So you end up with a permanent record

of the history of the water that the fish was swimming in.

So to get that record out of the otolith,

we cut very thin sections out the middle of the otolith.

And then we polish those thin sections,

mount them on a slide, bring them to this machine,

and it has a state of the art laser

that is used to sample the different types of elements

that are recorded in the rings.

So if this fish were exposed to the oil spill,

you would see unique elements showing up in this transect.

So what we're looking for is,

number one, whether or not the fish was exposed

and, number two, whether or not the fish

experienced slower growth rate after it was exposed.

Slower growth rate in fish

generally translates into higher death rates.

So growth rate is not a trivial thing.

If we see that there was a reduction in growth rate

associated with exposure to the oil,

then that means something negative

is likely to be influencing the population.

We have a lot of samples of important recreational

and commercial species, including red snapper.

We have large predators.

We have small fish from the deep ocean

that people generally never see,

even if you spend your entire life on the Gulf,

things that we've trawled up

from the very deep part of the Gulf of Mexico.

So we have a comprehensive spectrum of species

that we'll be looking at.

>>NARRATOR: Studies suggest

that the oil in the water column is diluting

and some of its components are being broken down by microbes.

As more time passes, experts say it is becoming more difficult

to find traces of oil in their water samples.

>>The one place that still seems to be at potential risk

is the sedimentary environment,

both in the shallow but also in the deep marine system,

where the plume was, and in that region.

>>NARRATOR: To study the sediments,

experts collect samples with a device called a multicore.

>>There's a central column that has eight separate cores

that are set up that, when the device hits the sediment floor,

that main column impales itself into the sedimentary system,

closing, then, these vacuum-tight seals.

And then the activated sample pulls up,

a bottom arm swings underneath the core

and traps the core material inside

and brings it to the surface.

>>Depth is at 1,002 meters.

>>NARRATOR: Sediment samples are cut into thin slices

and spun in a centrifuge to separate the water from the mud.

This water, called pore water, is then analyzed for toxicity

and the presence of hydrocarbons.

>>This is a shape and a region

that's characteristic of petroleum.

We do need to do further analyses to say, "Oh, this is...

This is exactly one compound or another compound,"

and I'm in the process of doing that right now.

We've got some PAH standards.

PAH stands for polycyclic aromatic hydrocarbons,

and those are some of the most toxic compounds

that are in the petroleum mixture.

So what I'll do is I'll analyze those known standards,

and I'll be able to compare those to what I've seen

in the natural environment.

>>NARRATOR: PAHs are not only

some of the most toxic components of oil,

but they also take a long time to break down.

To date, USF scientists have found that pore water samples

from the sediment cores have tested positive for toxicity,

as well as the presence of hydrocarbons.

Many of those samples were taken in an area

known as the De Soto Canyon.

>>We knew from prior history that

that was a very important area for fisheries.

Canyons can also focus the downward flux of material,

as well.

So we anticipated that that might be an area

where we will also see an impact on the seafloor.

>>The sedimentation rates

in those areas in the De Soto Canyon

is about 0.3 millimeters per year-- 0.3--

so in three years, you get one millimeter.

That's under normal conditions.

What we're recognizing is that the sedimentation rate

has increased by about an order of magnitude.

So now we're looking at three to ten millimeters per year,

so a significant increase in sedimentation rate.

And the question is why?

And so there are a number of hypotheses.

The most prevalent one is the blizzard hypothesis,

and that is that the oil droplets,

maybe with the addition of the dispersants,

has lent itself to a very sticky type material

that aggregates other biological material,

and it ballasts it so that it eventually sinks.

And if there's enough of this,

you can actually smother the habitat below.

>>NARRATOR: Another theory on how the sediments

and marine life on the bottom of the sea may have been impacted

is known as the bathtub ring hypothesis.

>>The plume, as it impinges on the continental slope,

would leave a bathtub ring of petroleum products.

>>NARRATOR: In some areas, the small creatures that live

on the bottom of the ocean appear impaired or dead,

and scientists say more research needs to be done

to understand what is happening to the ecosystem.

Past oil spills, such as the "Exxon Valdez" in Alaska

and the Ixtoc spill in the southern Gulf of Mexico

have shown that toxic oil

can persist in the environment for decades.

>>The Gulf of Mexico is

one of the three largest oil provenances in the world.

Oil drilling, oil and gas exploration

in the Gulf of Mexico is here to stay.

>>We really need to have this well thought out

in terms of different scenarios,

and that can only occur if you've got research

that's relevant to the different problems that might occur.

We need to actually make some serious investments in this

so that the next time around-- and there will be a next time--

that we're not sort of offering platitudes

as opposed to actually having

hard quantitative information available.

>>NARRATOR: Many questions remain

about the long-term impacts of this oil spill.

Researchers from the University of South Florida

and many other institutions are doing what they can

to better understand the full implications of this disaster.

>>A lot of people are working very hard,

doing methodical tasks,

and often it's not until later that you realize

the significance of what you've found.

It'll take many years before we understand the impact,

and it'll take even longer

before we can put the impact into context.

Putting the spill into context

is definitely something that will take decades.

>>Major funding for this program

was provided by the Batchelor Foundation,

encouraging people to preserve and protect

America's underwater resources.