NOVA

NARRATOR

It covers more than two-thirds of the earth. Its power is tremendous. Its importance to life, unquestioned. But now, something is changing in the sea. Threatening some of our planet's most spectacular treasures...

GRETCHEN HOFMANN

They can move, they can adapt, or unfortunately, they die.

NARRATOR

And attacking the ocean's fundamental web of life. Scientists are in a race against time to discover the real risks and come up with solutions. Off a remote island,

an amazing discovery

a spot that could hold the key to our future. We really hit a jackpot. This is such a scientific goldmine, like nowhere else in the world.

NARRATOR

Can we crack the code of a rapidly changing ocean to understand what it means for life before it's too late? "Lethal Seas," right now on NOVA.

Major funding for NOVA is provided by the following

Shouldn't what makes each of us unique of the sea,

a natural wonder

a coral reef filled with exotic creatures. Reefs like these aren't just stunning to look at. They're some of the most fertile places on earth, home to about a quarter of all species living in the seas. Now, this abundance of life is under threat by an invisible killer, one that's taking its toll not just here, but in our own backyard. Off America's northwest coast, the riches of the sea look like this.

Pacific oysters

a keystone of a $250 million shellfish industry. But not long ago, a mysterious threat emerged from the depths, putting the oysters and all who depend on them in jeopardy. Including oyster growers like Mark Wiegardt. Mark and his wife Sue Cudd run an oyster hatchery. In giant tanks of seawater, they grow baby shellfish called larvae, the foundation of the region's oyster population. Business was booming, until recently.

WIEGARDT

We first noticed a real solid change in 2007. We actually could not produce any larvae at all, and that definitely gets your attention.

CUDD

All of the larvae in the whole place were pink. They were not feeding. They looked terrible. We just knew they were all going to die.

NARRATOR

For months, the couple struggled to solve the mystery of the dying baby oysters.

WIEGARDT

We saw behavior in the larvae that we'd never seen before. They would circle around and then just kind of lay on the bottom. We call them lazy larvae. They'd actually dissolve in the water, and we didn't know what was going on.

NARRATOR

Sue hunted for clues under the microscope and found some disturbing evidence.

This is a magnified image of a healthy larva

a one-day old oyster. It's already started producing its shell. And this is what Sue was seeing in her microscope. The shell was deformed and pitted. The question was, why? The couple searched for a possible killer, but they never suspected that the culprit could be the seawater itself-- specifically, the water's pH.

WIEGARDT

I think the initial reaction from a lot of people was, "Don't worry about the pH of the water. That's never going to be a problem." It was a problem. The pH was dropping too low.

NARRATOR

pH is the standard measurement for acidity. The lower the pH, the higher the acidity. One of the hatchery workers suggested they run a simple pH test on the water in the oyster tanks-- water pumped from the bay. The results were shocking. The acidity of the bay water was a staggering six times higher than normal seawater. The baby oysters couldn't handle it.

WIEGARDT

What we've realized about the chemistry of the water is, is it's everything. If the chemistry's not right, the larvae can die, they can stop eating, they can stop growing. Basically, you're not able to grow larvae.

NARRATOR

With the mystery solved, the hatchery has found a temporary solution to the problem. Soda ash, a common water softener, lowers the acidity back to a level most of the young oysters can tolerate. Now enough baby oysters survive and grow so that Mark and his crew can transfer them out into the bay, but at a huge cost.

WIEGARDT

We pump 75,000 to 100,000 gallons a day, and that's a lot of... You're making your own special seawater. And there's goodies in the water the larvae like that I don't even know about that, you know, Mother Nature provides. So how do you duplicate what they like? It's a very tough question.

NARRATOR

Mark and Sue are not alone in their struggles. Fisheries throughout the Northwest are having the same problem-- water chemistry that's changing, shellfish that won't grow-- and scientists are finding it's not just here. Samples taken around the globe over the last 40 years reveal that average ocean acidity is increasing by about five percent every decade. Why is this happening? It turns out the driving force of ocean acidity is the same thing that's responsible for global warming. When we burn fossil fuels, they release carbon dioxide gas, or CO2, into the atmosphere. Much of that CO2 blankets the planet and raises the global temperature. But about a quarter of that gas is absorbed into the oceans. At first, scientists thought this was beneficial since the more CO2 that goes into the ocean means less in our atmosphere, reducing the warming effect.

GRETCHEN HOFMANN

Oceanographers knew for years that carbon dioxide from the atmosphere was absorbing into the oceans. And everyone thought, "Oh, perfect. "This is a service that the ocean is performing for us, "storing the gas that we're releasing as... It's a pollutant, it's a product of our activities." And so everybody thought, "Ooh, this is awesome!"

NARRATOR

But scientists soon realized that this service comes at a cost. The extra carbon dioxide absorbed by the ocean is dramatically changing the water's chemistry. We're dissolving 30 million metric tons of carbon dioxide into the surface of the ocean each and every day. And that is what's driving down the pH, or increasing the acidity. This is how it works. When carbon dioxide dissolves into the ocean, it reacts with water, H2O, to form a weak acid called carbonic acid. This almost immediately breaks apart, releasing hydrogen ions. Those are hydrogen atoms stripped of their electrons. This is what increases the water's acidity, and it can have a devastating effect on marine life, like oysters. Healthy baby oysters are busy building their shells. They pull the ingredients they need from the surrounding water, including calcium and a substance called carbonate, combining them into a tough matrix, calcium carbonate. But when too much carbon dioxide gets into the mix,

the resulting acid can radically alter one crucial ingredient

carbonate.

GREEN

There's plenty of calcium in the ocean. The carbonate is kind of what we call the limiting ingredient. There's not a lot of carbonate.

NARRATOR

When acidity rises and there are lots more hydrogen ions floating around, they react with carbonate, taking away this essential molecule.

GREEN

Instead of carbonate being all over the place, they're few and far between. And so what happens is physiologically, it's just much more difficult to make shell.

NARRATOR

Without enough carbonate in the water, the baby oysters simply can't build their shells, and as a result, they die. It's not just oysters that need carbonate to survive. The changing chemistry of the ocean threatens all kinds of shelled creatures. Scientists now face an urgent challenge to understand what this will mean for life in the sea. Along with the oysters, how many other species will struggle to survive?

GARETH LAWSON

From a biological standpoint, predicting what will happen to individual animals, populations, and ecosystems is incredibly difficult. I don't think right now we have a clue how that's going to change the development of any given species and then, well, how one species grows up influences its prey and it influences its predators and it influences its competitors. And so it is really complicated.

NARRATOR

The problem is most urgent here, on the world's coral reefs. These are some of the most spectacular places on earth, filled with exotic creatures. Coral reefs occupy less than one percent of the ocean floor, yet they provide a home for at least a quarter of all marine species. And they're a key resource for survival for an estimated half a billion people. The foundations of these beautiful reefs are made of the skeletons of countless corals built up over thousands of years. Like the oyster shells, these skeletons are made of calcium carbonate, sometimes known as limestone. And this makes them especially vulnerable to the ocean's rising acidity. Corals are incredibly sensitive to high carbon dioxide conditions because they're forming a skeleton that is made out of limestone, and limestone and acid just don't go together. Katharina Fabricius has spent a lifetime diving on some of the world's most pristine reefs.

FABRICIUS

It's just one of the most amazing ecosystems in the world, and seeing them degrading over time, it's just a real shame. It's also a moral and ethical responsibility for us to protect the reefs for our children and our grandchildren.

NARRATOR

Many coral reefs worldwide are already suffering because of warming seas. How will the changing ocean chemistry affect them?

Katharina believes she's discovered a clue

a very special reef located in remote Papua New Guinea.

FABRICIUS

The site is the straight stretch in the reef flat there. We'll be able to see the bubbles from the surface.

NARRATOR

Set among the volcanic islands of Milne Bay lies one reef that Katharina found by accident more than a decade ago. It's a place where the water looks a bit like champagne, filled with streams of gas bubbles rising up through the sea floor caused by volcanic activity. Samples reveal they are pure carbon dioxide. And just like the carbon dioxide that's mixing into the oceans from the atmosphere, these bubbles react with water to form an acid, lowering the water's pH.

FABRICIUS

It was just so exciting, and I realized, "Maybe we can use that as a natural laboratory."

NARRATOR

There's so much carbon dioxide, the acidity is much higher than normal. In fact, the water chemistry here today is similar to what scientists think could happen to the rest of the ocean in 50 to 100 years if carbon dioxide levels continue to rise. So it could offer a unique window into the future of coral reefs across the globe. So I thought, "Bingo, that's it, we've got to go back!" We're going to the site Ili Ili Bua Bua, which is the best bubble site we've got. Katharina and her team are now into their fourth year of study here, one of only a handful of coral reefs in the world with naturally high acidity. My hope is very high that these guys here are cracking it and producing the world-class science that is so needed to understand ocean acidification. For the team, these waters offer a unique opportunity to compare two marine environments

very close together

the control site, where the ocean chemistry is normal, and the bubble site, where carbon dioxide is dramatically raising the water's acidity. How is life here, the corals and the creatures that depend on them, responding to the changes? Are some adapting to new conditions? How many are struggling to survive? With just two weeks to get the work done, the team dives into their experiments. Each of us is focusing on two or three different projects. I'm looking at how the conditions for corals is changing. That is stuff you cannot do in the laboratory.

NARRATOR

Corals are unusual creatures. Each of these branching clumps is actually a colony made up of thousands of tiny building blocks called coral polyps.

FABRICIUS

This is all one organism, but like a plant having individual leaves, the corals have individual polyps that are feeding separately from each other. They can share the food, but each polyp can respond to plankton touching its tentacles and grabbing it. Once they're digesting it, they're spreading the juices across the colony.

NARRATOR

Corals are happiest and healthiest where the water is clear and well-lit by the sun and where they don't get too much competition from seaweed. But their unusual lifestyle makes them especially vulnerable to a changing environment.

FABRICIUS

Corals are actually animals, but they're glued to the ground like a plant is. They're not able to pack their bags and move to another site if the conditions are no good for them.

NARRATOR

Where the carbon dioxide bubbles are most intense, few corals seem to be finding the conditions favorable. These large, extremely tolerant corals are called porites. They have thick skins and now dominate the reef. The colorful branching corals and soft corals that flourish in most coral reefs are gone. The team works around the clock. In all kinds of weather. Some days, nothing goes according to plan. I think there is some problem with one of the generators. One of the exhaust pipes had a bit of a breakdown. Underwater conditions are difficult.

LAETITIA PLAISANCE

This site, we have massive rocks, so it's really hard to drill inside the structure.

NARRATOR

And some of the coral experiments have become dinner for some hungry snails. At least 50% of the little coral branches we made have been eaten by these snails. Yeah, not happy.

FABRICIUS

Experiments by nature quite often fail. It's requiring a lot of patience. But eventually, we'll sort it and we'll find some other ways to test the same questions.

NARRATOR

While Katharina is studying the impact of high acidity on the corals themselves... So I probably first jump in......another team member, Laetitia Plaisance, is studying the many other sea creatures who depend on them. Where the water chemistry is normal, the coral gardens of Papua New Guinea are among the richest on the planet, home to more than 500 species of coral. And hundreds of thousands of different kinds of tiny sea creatures. The entire ecosystem rests on a coral foundation built from calcium carbonate. Everything is a balance in the ocean. The reef is made of calcifying organisms, so that means they need a higher pH to be able to build their skeleton. And this skeleton then provides the structure of the reef, where all the other associated species can find shelter, and they can mate and they can feed and they can hide in that structure. Today,

Laetitia is focusing on one particular habitat

the dead coral head. I'm on my way to find a coral head. A nice, dead coral head.

NARRATOR

Living coral heads provide homes for tiny fish and many other animals. Even on normal, healthy reefs, coral heads will eventually die, but their calcium carbonate structure remains, and just like a dead tree, new creatures move in. Laetitia collects dead coral heads from both the normal site and the bubbly site, where acidity is much higher and the pH is lower. Will she find the same variety of species living in both locations? To find out, she cracks open the coral heads, hunting for the creatures hidden inside their nooks and crannies.

PLAISANCE

I'm searching for the crabs and the mollusks, and here is a little ophiuroid trying to escape. Another sea cucumber I think here, all part of the food chain. And if you miss a link in the chain, the rest of the chain can't continue, can't go on. So yes, all those little pretty insignificant species are extremely important.

NARRATOR

When she takes apart the coral head from the control site with normal pH and acidity, she's impressed by the number of creatures she uncovers.

PLAISANCE

This morning, we collected a nice dead coral head from the control site, which meant regular conditions with beautiful reef. And when I opened the coral head, it was filled with life, abundance, and diversity. So we have plenty of different species of crustaceans here, lobsters and crabs and shrimps.

NARRATOR

But examining the coral head from the bubble site, even before Laetitia breaks it open, she is concerned. The first thing that I noticed with this coral head is that it's covered with this type of algae. And the problem really is that this type of algae does not hold much diversity, which I'm used to seeing in other sites where the pH is much higher. The collection of life looks more limited, but to make sure, to get an exact inventory of all the different species, Laetitia analyzes the DNA of the samples she collected. For example, two tiny shrimp may look alike, but they could actually be different species. A DNA test will reveal precisely how many different species live here.

The DNA results confirm what Laetitia suspected

the highest species diversity is at the control site, where the acidity and pH are normal. But as the acidity goes up and the pH goes down, the number of species drops dramatically. For each type of animal, only one or two species are tolerating the high acidity, and the rest have disappeared.

PLAISANCE

So you have the same kind of shrimp a hundred times, when in the regular pH conditions, you have a hundred different species.

NARRATOR

Laetitia finds that the high CO2 site has 30% less diversity of small sea creatures, like hermit crabs, shrimp, and starfish, than the control site. For Laetitia, this is troubling news.

PLAISANCE

The reason why this group is very important is because it's the basis of the food chain in coral reef. The fish feed on those tiny creatures, so if those tiny creatures disappear, the fish community is going to change and evolve as a result of this loss.

NARRATOR

It appears that changes in acidity aren't just affecting the corals themselves, but hundreds of species living at the bottom of the food chain. And if those at the base of the food chain are at risk, so are all the creatures that rely on them for survival. These kinds of changes aren't just happening at coral reefs. Cold water absorbs more carbon dioxide than warm, so acidity could rise in the Arctic and Antarctic seas more quickly. And that could mean trouble for the creatures here that, like coral and oysters, rely on carbonate to build their shells and skeletons. Back it up, please. Aboard the Aurora Australis, the Australian Antarctic Division's research vessel, scientists are studying tiny plankton, some the size of a pinhead.

DONNA ROBERTS

Now we get to throw that back over the side.

NARRATOR

Donna Roberts has spent much of her career in the Southern Ocean, and her favorite kind of plankton are tiny animals called pteropods. These almost transparent sea snails swarm in vast numbers in the colder waters of the Arctic and the Antarctic oceans. They are at the bottom of the food chain, providing food for whales, fish, and ultimately, us.

ROBERTS

The pteropod shells are gorgeous. It's just like a garden snail, but instead of having one slimy foot, it's evolved to live in the ocean with wings. Scientists call pteropods the "potato chips of the sea" because they're meaty and a lot of things eat them, but they've got that added little crunch.

NARRATOR

Tucked away in this cold room at the University of Tasmania are pteropod samples from Antarctica dating back to 1997. Donna is analyzing their shell weight to see if rising acidity has affected them.

ROBERTS

It does matter if a little organism is losing weight because it's a measure of how healthy they are, so if their shells become thin, then they are going to put more of their energy towards building what little shell they can than reproducing.

NARRATOR

Pteropod shells collected today are 35% smaller and more fragile than those caught a decade ago, yet another sign of rising ocean acidity.

ROBERTS

So this is a healthy set of shells that we collected in 2002, and I'll just show you for comparison what unhealthy shells look like. So you can see this one here has lost a segment of shell, and this one here is incredibly thin, very paper thin. Shells like this often fall apart in my hand when I'm trying to weigh them.

NARRATOR

Scientists say that, like the baby oysters, there could soon come a point at which the levels of carbon dioxide will be too great for these beautiful little sea butterflies.

ROBERTS

Most people have not heard of what a pteropod is, but they are vastly important. They are holding up the entire Southern Ocean food web in places.

NARRATOR

Pteropods are a key food source for lots of animals that swim the seas, not only in the southern oceans, but in the northern oceans as well. So what would happen if pteropod populations decline, or even disappear, around the globe because of rising acidity? The ecosystem effects of removing all the pteropods are just completely unclear. If we take them all away, we really don't know what the effects might be, but they may be quite dire for the things that feed on them. Among the things that feed on pteropods are things we feed on, like salmon.

MARK GREEN

If you're a pink salmon, you can't just remove 10%, 15% of a juvenile pink salmon's diet and expect it to, you know, just, "Oh, well, I'll just eat a little more of this instead." It's not evolutionarily hard-wired to do that. So when you start removing huge components of what other individuals eat, what other species eat, that's a problem.

NARRATOR

If higher acidity reduces or wipes out populations of creatures at the bottom of the food chain, the consequences could be bad for those further up. The worst possible scenario would involve a chain reaction of extinction resulting in mass die-offs throughout the oceans. It has happened before. The fossils that trace the history of life in the ancient oceans reveal dramatic moments when suddenly, many living things went extinct. We think many of the big extinction events in the past have been related to some rapid event, whether it was an asteroid impact or some rapid large increase in volcanism. Temperature was changing, ocean chemistry was changing. That's where we see the big extinction events. The most famous extinction was 65 million years ago, when the dinosaurs disappeared. But an even bigger catastrophe hit the oceans 250 million years ago, when the Permian Era ended. The leading theory is that massive volcanic eruptions caused carbon dioxide levels to spike quickly. The result was what's now known as the "Great Dying," when up to 96% of all marine life went extinct, including many coral reefs. If acidity changes slowly, many creatures may be able to adapt and evolve to cope with the new conditions. But sudden changes are often dangerous for life.

DONEY

On evolutionary time scales, organisms are adapting to their environment. The environment's changing and life is always changing. The more rapid that change, the harder it is for the organisms to adapt.

NARRATOR

And today, the burning of fossil fuels is releasing so much carbon dioxide, it's changing the environment of the ocean very rapidly. Scientists fear that if carbon dioxide continues to rise at high speeds, we could have a major extinction event on our hands. The rate of change is happening much, much faster than these plants and these animals can adapt. Unless it happens at a much, much slower rate, evolution will not have an opportunity to keep up with the change. Perhaps nowhere on earth are the plants and animals of the sea more at risk than on coral reefs. Half a billion people rely on these unique ecosystems for their survival. The fish that live around reefs form a major part of the human diet. So how will rising ocean acidity affect these animals? In addition to messing up the base of the food chain, will the changing chemistry have any direct effect on the fishes' own bodies? Researchers like Danielle Dixson are trying to find out. Until now, most of her work has been in the lab, but today, she's joining the team in Papua New Guinea, where at one unique reef, carbon dioxide bubbles are raising the water's acidity to extreme levels.

DIXSON

The thing about this location that makes it really, really interesting is that these fish have been living in this CO2 situation for a very long time. You can see where the CO2 is coming up there, so that's the CO2 seep site...

NARRATOR

Philip Munday is Danielle's former professor and collaborator. In experiments back at the lab, they exposed fish to high levels of CO2 and saw alarming results. The damage wasn't done to the fishes' skeletons, but to their brain chemistry and their behavior.

MUNDAY

What we do see that's really dramatic is the changes in their behavior. So things like how they respond to chemical cues in the water changes, their response to sound changes. And what's really cool here is that we can come to these seeps and we can see fish that have probably been living for months, maybe even years, under a high CO2 environment and see if their behavior is still affected.

NARRATOR

The team wants to find out if the behavior they saw in the lab will be repeated in the wild, where some fish have grown up in high CO2 conditions throughout their lives. They'll compare the behavior of the fish living both near and far from the carbon dioxide bubbles. First, they'll test how they respond to chemical cues in the water-- in other words, their sense of smell.

MUNDAY

Baby fish in particular have very good noses. It's not on the end of their face, but they have nostrils, and water comes in, and there's sensory cells inside the nostril, and then water goes back out, very much the same as we do.

NARRATOR

Just as land animals use their noses to detect certain molecules that float in the air, fish noses can sense molecules moving through the water. Their sense of smell is critical for their survival. They use it to catch food, find their way home, and even to sense danger.

DIXSON

There's a lot of things in the water that produce a lot of smell. There's predators in the water that are trying to feed. There's prey in the water that things are trying to feed on. The corals themselves, they're also releasing chemical cues. Pretty much everything uses chemistry underwater, so yeah, reefs would be a pretty smelly place.

NARRATOR

The first step for this experiment is to catch some fish.

DIXSON

They're very easy to catch. Just a little bit of clove oil, and then you can use your hand to waft them out of the coral and grab them in a net.

NARRATOR

Next, they must catch a predator fish. So I got a fish. Danielle wants to test the smaller reef fishes' ability to identify their predators, like this rock cod, by their smell, a crucial survival strategy for animals on land or sea.

DIXSON

This fish is going to be used to make predator odor. I'm just going to soak it in some water, and then the cues from the fish will come out in the water and I'll be able to test little fish to see if they can identify the predator cues over other cues.

NARRATOR

For this experiment, water with the predator odor is being pumped into the top side of the flume. The bottom side has normal off-shore seawater.

DIXSON

The fish that we have in the flume right now was taken from the control reef where no CO2 bubbles are happening. The fish identifies the predator through smell alone and stays in the off-shore water side where no predator smell is.

NARRATOR

The next fish has grown up in the carbon dioxide bubble site, where the water acidity is higher.

DIXSON

Now the fish is sitting in the water that has the predator scent.

NARRATOR

Instead of being repelled, the fish seems attracted to the dangerous smell.

DIXSON

We've found that the CO2 is affecting the fish's cognitive ability. So it can identify the smell of a predator, but something's wrong with its brain that it's having a hard time identifying it as a bad thing. It's just identifying the smell.

NARRATOR

After testing dozens of fish, Danielle finds that the fish that grow up in higher acidity don't avoid the predator smell, behavior that makes it much more likely that they'd end up as somebody's dinner. In addition to smell,

Danielle wants to test another survival instinct

the ability to hide. On these reefs, many fish live among the corals, using their branches for protection. These fish are like candy on the reef. They're really liked to be eaten. It is in their best interests to be closer to their habitat so they can retreat back to it and they're not picked off as much by predators.

NARRATOR

Danielle tracks how adventurous the little fish are. Which ones will play it safe and stick close to the coral shelter? This one is from the control site where the conditions are normal. You can see it retreats right into the coral. It might be exploring the habitat of the coral, but it's not really exploring the tank. The fish will stay like this for the entire trial in general. The next fish comes from the carbon dioxide bubble site.

DIXSON

You can see it's checking out the water a lot. It's going quite far from the coral. It's not really retreating back into the coral. Being bolder can make you grow faster and get bigger, but it also makes you a lot more susceptible to predators.

NARRATOR

Danielle tests several fish. The small fish living in the higher acidity are consistently more adventurous-- behavior that could put their lives at higher risk. Researchers don't know yet how all the different kinds of fish that live in the sea will be affected in higher acidity. Some are likely to cope better than others. And some may find some surprising benefits. At the bubble site, one form of life that's thriving is the seagrass.

FABRICIUS

Seagrasses can live in very high CO2 environments. They actually like it because seagrasses, like the terrestrial plants, they do take in the carbon dioxide and convert it into sugars.

NARRATOR

For plants, carbon dioxide is a fuel. They use sunlight to turn it into sugar, leaving oxygen as a waste product. The rich supply of carbon dioxide here is fertilizing these seagrass beds. The thick lawn of seagrass appears to be an important nursery for baby fish. Biologists are hoping that many of today's fish will find a way to survive in an ocean with more carbon dioxide and higher acidity. Their bodies may be able to adapt to changing conditions possibly by turning on particular genes.

MUNDAY

There are mechanisms that might allow them to adjust to a high CO2 world. Some individuals will have better genes for that particular environment, so they pass their genes on and you get genetic adaptation.

NARRATOR

Marine biologists are eagerly hunting for any signs of genetic adaptation to a rapidly acidifying ocean. Today, the race is on to find creatures that carry genes that would help them survive, and the best places to look are the ones where ocean acidity goes up and down. On the West Coast from Washington State down to California, there's a seasonal upwelling of carbon dioxide from the deep ocean, lowering the pH and raising the acidity. Gretchen Hofmann is trying to find out how the marine life here copes with a fluctuating pH.

HOFMANN

One thing that's unique about the California coast here is that we have upwelling. And this is where wind blows across the surface of the ocean, starting in the springtime, and this wind brings up deep, cold, CO2-rich water to the shores. And that water has a really low pH, and this low pH water has an impact on the biology on the shores.

NARRATOR

One creature that seems to have adapted to the ocean's low pH and high acidity here is the spiky sea urchin. These are the lawnmowers of the sea. They play a vital role keeping ecosystems healthy by devouring seaweed which, without the urchins, could grow out of control. Unlike the oyster, which is struggling to build its shell in the high acidity of the Northwest Coast, the sea urchin seems to be flourishing even though it sports a shell

constructed of the same material

calcium carbonate. Gretchen believes the key to its success may lie in its genes. We found that populations, say, from the north in Oregon that are really tougher in the face of these pH changes, they were expressing genes in a different way than sort of the wimpy California urchins were, that they were turning on more genes that would help them make their skeleton.

NARRATOR

By turning on certain genes, the northern sea urchins became more efficient at building their calcium carbonate shells, even when the surrounding water had higher acidity. Gretchen wonders if this life-saving gene could be passed on to the more vulnerable urchins in the south. To find out, she sets up a cross-breeding experiment. The sperm from both northern and southern males is used to fertilize eggs from the less hardy southern females. Once the larvae begin to mature, Gretchen compares the two samples.

HOFMANN

Now we're interested in measuring their skeleton, and the way I think about a sea urchin larvae is that it's like a free-standing backpacking tent. So the skeleton are actually like the tent poles-- that's the thing that's made of calcium carbonate-- and that's part of their body that could be challenged to form under ocean acidification conditions.

NARRATOR

Amazingly, the experiment reveals that the northern urchin's tolerance to high acidity is passed on genetically to the southern female's young larvae.

HOFMANN

What we've learned is that larvae that have fathers from the northern populations actually retain their body size. They stay bigger even in the face of low pH. So it does matter who your daddy is in this kind of experiment. We know now that there are populations that have the genetics that will allow them to adapt, and we know how to look for them.

NARRATOR

Researchers are looking all over for other marine life that is surviving in more corrosive waters. Especially corals, since so far, they seem to be some of the most vulnerable creatures in the sea. About a thousand miles northwest of Papua New Guinea, off the Pacific islands of Palau, sits another coral reef where the acidity is naturally high. Here, there are no carbon dioxide bubbles rising up from below. The acidity seems to be caused by the density of aquatic life, combined with very slow water circulation in these shallow lagoons. Despite the high acidity, many corals here appear to be healthy. Anne Cohen is trying to figure out why.

COHEN

We believe that we have found one coral reef community which for some reason that we don't quite yet understand-- it could be a genetic adaptation or it could be a combination of environmental factors-- allows them to survive and cope with these low pH conditions.

NARRATOR

One important feature of this environment may be that in these shallow lagoons, the corals are extremely sheltered from any waves or storms. And that may be the key to their survival so far. For marine scientists, places like these are precious. We have to put those systems at high priority for protection. Those systems might be the only ones that are left at the end of this century. Unlike this unusual spot in Palau, most reefs have to cope with powerful storms from time to time, and they rely on fast-growing corals to quickly rebuild their foundations. Back in Papua New Guinea, Katharina Fabricius would love to find evidence that the corals here, bathed in carbon dioxide bubbles produced by volcanic activity, are adapting, finding ways to be resilient in spite of the higher acidity. Here, hopefully, some organisms have gotten used to the high carbon dioxide concentrations, which would be a good thing because it would tell us that maybe there is a future for coral reefs after all. 14 months ago, Katharina placed over 100 blank tiles at her study sites just in time for the annual coral spawning, hoping to compare the growth of baby corals in areas with normal and high acidity. The spawning of the coral is one of the most spectacular natural events on earth. The corals synchronize their spawning with the lunar cycle, releasing billions of eggs and sperm, usually on the same night. Within a few days, the tiny coral larvae must find the right place to call home. Will these baby corals settle and grow on Katharina's tiles? Or will the high acidity ruin their chances? Now she'll find out. The first tiles are from the control site.

FABRICIUS

They're looking fantastic. All the pink color is coralline algae, which are really important for the health of the reefs.

NARRATOR

This pink coralline algae is often called "the cement of the reef." It's one kind of algae the corals actually do like. Young corals are genetically programmed to zero in on it because it provides a strong foundation for their growth. But it's made of a type of calcium carbonate that will dissolve even faster than the corals if the pH drops too low. Katharina now moves to the high acidity bubble site and collects the tiles there. It takes hours to inventory exactly what's growing on all the tiles. The ones from the control site, where acidity is low, have cultivated a healthy batch of young corals.

FABRICIUS

The tiles from the control site already have got a fair number of large coral colonies established. Baby coral settled on the edge here is growing quite happily. So that's about one year old. Coralline algae here, the pink stuff. There's a spec here. There's one sitting here right at the edge. I found up to 19 coral settlers on this very small space. Not all of them will survive, but still, it's very good for the coral reefs to establish.

NARRATOR

But the tiles from the carbon dioxide bubble site tell a different story. We found hardly any coral recruits on them. There's no pink left, no coralline algae. We're getting a lot of seaweed that are occupying the space for coral to settle. The fact that there are so few coral recruits is of real concern. I didn't expect the differences to be so stark. The expedition's nearly over. The findings here have been discouraging. Along with the scientists, the locals are concerned about the future of their coral reef.

FABRICIUS

The coral reefs will still be there in 50 or 100 years' time, but they will look very different is our prediction. There will be less of those branching corals and there will be possibly less fish as well, which is of real concern because it's important for food.

NARRATOR

Right now, carbon dioxide levels are rising rapidly. And if that keeps going, the acidity of the ocean will continue to rise as well.

COHEN

The problem now is that you can't fence off a coral reef island or a fringing reef or a barrier reef and protect it from acidification. This is a global threat.

NARRATOR

With coral reefs in many places already vanishing at a rate of one to two percent every year, finding a solution is critical. So far, evidence that coral can adapt is slim. And many marine biologists are asking, "Is it realistic to expect the creatures of the sea to adapt to an ocean that is changing so rapidly?"

Or should we go to the source of the problem

the rising carbon dioxide in our atmosphere and in the seas caused by the burning of fossil fuels? The best solution is to reduce the emissions to the atmosphere or capture the carbon dioxide before it gets into the atmosphere. There's no way to save coral reefs without stopping greenhouse gas emissions. I mean, there is absolutely no practical solution to protect coral reefs from warming and from ocean acidification if you don't stop carbon dioxide emissions in the world. If we know what's causing it, why don't we just fix the cause and not twiddle our thumbs for 20 or 30 years trying to sort things out?

NARRATOR

And if carbon emissions aren't cut,

many are troubled by the question

What will happen to life in the sea? It's a big question mark really, what the ocean's going to look like, but it is going to look a lot different, and it is not going to be as resilient as it is today.

McCORKLE

We're sort of crossing our fingers that there's all these complicated web of changes and that somehow, we're going to be happy with the outcome. And I just think that's a bigger risk than we ought to take. My computer, my iPad, I knew that I was being hacked. In the past, it may have been weapons of mass destruction. The greatest threat today is the keyboard.

MAN

This is not hackers in their basement. When it first came up, my mouth was wide open, going, "Oh, my God." Malicious programs being able to literally blow things up.

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