By Usha Lee McFarling, Times Staff Writer
August 3, 2006
A Chemical Imbalance
Growing seawater acidity threatens to wipe out coral, fish
and other crucial species worldwide.
As she stared down into a wide-mouthed plastic jar aboard
the R/V Discoverer, Victoria Fabry peered into the future.
The marine snails she was studying — graceful creatures
with wing-like feet that help them glide through the water
— had started to dissolve.
Fabry was taken aback. The button-sized snails, called
pteropods, are hardy animals that swirl in dense patches
in some of the world's coldest seas. In 20 years of studying
the snails, a vital ingredient in the polar food supply,
the marine biologist from Cal State San Marcos had never
seen such damage.
In a brief experiment aboard the federal research vessel
plowing through rough Alaskan seas, the pteropods were sealed
in jars. The carbon dioxide they exhaled made the water
inside more acidic. Though slight, this change in water
chemistry ravaged the snails' translucent shells. After
36 hours, they were pitted and covered with white spots.
The one-liter jars of seawater were a microcosm of change
now occurring invisibly throughout the world's vast, open
As industrial activity pumps massive amounts of carbon
dioxide into the environment, more of the gas is being absorbed
by the oceans. As a result, seawater is becoming more acidic,
and a variety of sea creatures await the same dismal fate
as Fabry's pteropods.
The greenhouse gas, best known for accumulating in the
atmosphere and heating the planet, is entering the ocean
at a rate of nearly 1 million tons per hour — 10 times
the natural rate.
Scientists report that the seas are more acidic today than
they have been in at least 650,000 years. At the current
rate of increase, ocean acidity is expected, by the end
of this century, to be 2 1/2 times what it was before the
Industrial Revolution began 200 years ago. Such a change
would devastate many species of fish and other animals that
have thrived in chemically stable seawater for millions
Less likely to be harmed are algae, bacteria and other
primitive forms of life that are already proliferating at
the expense of fish, marine mammals and corals.
In a matter of decades, the world's remaining coral reefs
could be too brittle to withstand pounding waves. Shells
could become too fragile to protect their occupants. By
the end of the century, much of the polar ocean is expected
to be as acidified as the water that did such damage to
the pteropods aboard the Discoverer.
Some marine biologists predict that altered acid levels
will disrupt fisheries by melting away the bottom rungs
of the food chain — tiny planktonic plants and animals
that provide the basic nutrition for all living things in
Fabry, who recently testified on the issue before the U.S.
Senate, told policymakers that the effects on marine life
could be "direct and profound."
"The potential is there to have a devastating impact,"
Fabry said, "for the oceans to be very, very different
in the near future than they are today."
The oceans have been a natural sponge for carbon dioxide
from time immemorial. Especially after calamities such as
asteroid strikes, they have acted as a global safety valve,
soaking up excess CO2 and preventing catastrophic overheating
of the planet.
If not for the oceans, the Earth would have warmed by 2
degrees instead of 1 over the last century, scientists say.
Glaciers would be disappearing faster than they are, droughts
would be more widespread and rising sea levels would be
When carbon dioxide is added to the ocean gradually, it
does little harm. Some of it is taken up during photosynthesis
by microscopic plants called phytoplankton. Some of it is
used by microorganisms to build shells. After their inhabitants
die, the empty shells rain down on the seafloor in a kind
of biological snow. The famed white cliffs of Dover are
made of this material.
Today, however, the addition of carbon dioxide to the seas
is anything but gradual.
Scientists estimate that nearly 500 billion tons of the
gas have been absorbed by the oceans since the start of
the Industrial Revolution. That is more than a fourth of
all the CO2 that humanity has emitted into the atmosphere.
Eventually, 80% of all human-generated carbon dioxide is
expected to find its way into the sea.
Carbon dioxide moves freely between air and sea in a process
known as molecular diffusion. The exchange occurs in a film
of water at the surface. Carbon dioxide travels wherever
concentrations are lowest. If levels in the atmosphere are
high, the gas goes into the ocean. If they are higher in
the sea, as they have been for much of the past, the gas
leaves the water and enters the air.
If not for the CO2 pumped into the skies in the last century,
more of the gas would leave the sea than would enter it.
"We have reversed that direction," said Ken Caldeira,
an expert on ocean chemistry and carbon dioxide at the Carnegie
Institution's department of global ecology, based at Stanford
When carbon dioxide mixes with seawater, it creates carbonic
acid, the weak acid in carbonated drinks.
Increased acidity reduces the abundance of the right chemical
forms of a mineral called calcium carbonate, which corals
and other sea animals need to build shells and skeletons.
It also slows the growth of the animals within those shells.
Even slightly acidified seawater is toxic to the eggs and
larvae of some fish species. In others, including amberjack
and halibut, it can cause heart attacks, experiments show.
Acidified waters also tend to asphyxiate animals that require
a lot of oxygen, such as fast-swimming squid.
The pH scale, a measure of how acidic or alkaline a substance
is, ranges from 1 to 14, with 7 being neutral. The lower
the pH, the greater the acidity. Each number represents
a tenfold change in acidity or alkalinity.
For more than a decade, teams led by Richard Feely, a chemical
oceanographer at the National Oceanic and Atmospheric Administration's
Pacific Marine Environmental Laboratory in Seattle, have
traveled from Antarctica to the Aleutian Islands, taking
tens of thousands of water samples to gauge how the ocean's
acidity is changing.
By comparing these measurements to past levels of carbon
dioxide preserved in ice cores, the researchers determined
that the average pH of the ocean surface has declined since
the beginning of the Industrial Revolution by 0.1 units,
from 8.16 to 8.05.
Geological records show that such a change has not occurred
in 650,000 years, Feely said.
In April, Feely returned from a cruise to the North Pacific,
where he took pH measurements at locations the team first
sampled in 1991. This time, Feely's group found that the
average pH in surface waters had dropped an additional 0.025
units in 15 years — a relatively large change for
such a short time.
The measurements confirm those taken in the 1990s and indicate
that forecasts of increased acidity are on target, Feely
If CO2 emissions continue at their current pace, the pH
of the ocean is expected to dip to 7.9 or lower by the end
of the century — a 150% change.
The last time ocean chemistry underwent such a radical
transformation, Caldeira said, "was when the dinosaurs
Until recently, the ocean was seen as a potential reservoir
for greenhouse gases. Scientists explored the possibility
that carbon dioxide could be trapped in smokestacks, compressed
into a gooey liquid and piped directly into the deep sea.
Then the results of Jim Barry's experiments started trickling
A biologist at the Monterey Bay Aquarium Research Institute,
Barry wanted to know what would happen to sea creatures
in the vicinity of a large dose of carbon dioxide.
He anchored a set of small plastic rings onto the seafloor
to create an enclosure and sent a robot down to squirt liquid
carbon dioxide into the surrounding water. Then he waited
to see what would happen to animals in the enclosures and
those that happened to swim through the CO2 cloud.
Sea stars, sea cucumbers and sea urchins died immediately.
Eighty percent of animals within three feet of the carbon
dioxide died. Animals 15 feet away also perished in large
"When they were adjacent to the CO2 plume, pretty
much, it killed everything," Barry said.
Experiments in Germany, Norway and Japan produced similar
results. The evidence persuaded the U.S. Department of Energy,
which had spent $22 million on such research, including
Barry's, to pull the plug . Instead, the department will
study the possibility of storing carbon dioxide in the ground
and on decreasing emissions at their source.
Scientists say the acidification of the oceans won't be
arrested unless the output of CO2 from factories, power
plants and automobiles is substantially reduced. Even now,
the problem may be irreversible.
"One thing we know for certain is it's not going to
be a good thing for the ocean," Barry said. "We
just don't know how bad it will be."
Scientists predict the effect will be felt first in the
polar oceans and at lower depths, because cold water absorbs
more carbon dioxide than warm water. One area of immediate
concern is the Bering Sea and other waters around Alaska,
home to half of the commercial U.S. fish and shellfish catch.
Because of acidification, waters in the Bering Sea about
280 feet down are running short of the materials that corals
and other animals need to grow shells and skeletons. These
chemical building blocks are normally abundant at such depths.
In coming decades, the impoverished zone is expected to
reach closer to the surface. A great quantity of sea life
would then be affected.
"I'm getting nervous about that," Feely said.
The first victims of acidification are likely to be cold-water
corals that provide food, shelter and reproductive grounds
for hundreds of species, including commercially valuable
ones such as sea bass, snapper, ocean perch and rock shrimp.
By the end of the century, 70% of cold-water corals will
be exposed to waters stripped of the chemicals required
for sturdy skeletons, said John Guinotte, an expert on corals
at the nonprofit Marine Conservation Biology Institute in
"I liken it to osteoporosis in humans," Guinotte
said. "You just can't build a strong structure without
the right materials."
Cold-water corals, which thrive in waters as deep as three
miles, were discovered only two decades ago. They harbor
sponges, which show promise as powerful anti-cancer and
antiviral agents; the AIDS drug AZT was formulated using
clues from a coral sponge. Scientists fear that these unique
ecosystems may be obliterated before they can be fully utilized
Tropical corals will not be affected as quickly because
they live in warmer waters that do not absorb as much carbon
dioxide. But in 100 years, large tropical reefs —
called rain forests of the sea because of their biodiversity
— may survive only in patches near the equator.
"Twenty-five percent of all species in the ocean live
part of their life cycle on coral reefs. We're afraid we're
going to lose these habitats and these species," said
Chris Langdon, a coral expert at the University of Miami
who has conducted experiments showing that corals grow more
slowly when exposed to acidified waters.
Warm-water corals are already dying at high rates as global
warming heats oceans and causes corals to "bleach"
— lose or expel the symbiotic algae that provide vivid
color and nutrients necessary for survival. Pollution, trampling
by tourists and dynamiting by fishermen also take a devastating
toll. An estimated 20% of the world's corals have disappeared
"Corals are getting squeezed from both ends,"
said Joanie Kleypas, a marine ecologist and coral expert
at the National Center for Atmospheric Research in Boulder,
The question for scientists is whether living things will
adapt to acidification. Will some animals migrate to warmer
waters that don't lose shell-building minerals as quickly?
Will some survive despite the new chemistry? Will complex
marine food chains be harmed?
One laboratory experiment showed that a strain of shelled
plankton thrived in higher CO2 conditions. But most research
has shown that shelled animals and corals stop growing or
"We put a lot of faith in the idea that organisms
can adapt," Kleypas said, "but organisms have
probably not evolved to handle these big changes."
The best analogy to what is occurring today is in the fossil
records of a 55-million-year-old event known as the Paleocene-Eocene
Thermal Maximum, when the Earth underwent one of the most
abrupt and extreme global warming events in history.
The average temperature of the planet rose 9 degrees because
of an increase in greenhouse gases. Balmy 70-degree days
were common in the Arctic. The sudden warming shifted entire
ecosystems to higher and cooler latitudes and drove myriad
ocean species to extinction.
Geologists agree that a great warming occurred as a result
of greenhouse gases, but until recently were uncertain about
the volume of gas involved or how much the acidity of the
James Zachos, a paleo-oceanographer at UC Santa Cruz, made
an important discovery in 2003 by drilling into seabed sediments
more than two miles beneath the ocean's surface. This muck
contains layers of microscopic plankton shells. Their chemical
composition reveals what ocean conditions were like when
Zachos' international team analyzed sediments from a series
of cores taken from the floor of the Atlantic Ocean 750
miles west of Namibia. At the bottom of the cores, the team
found normal sediments, rich in calcium carbonate from shells
— the sign of a healthy ocean.
But higher up, at a point in geologic history when the
last major global warming event occurred, the whitish, carbonate-rich
ooze gave way to a dark red clay layer free of shells. That
condition, the researchers concluded, was caused by a highly
acidified ocean. This state of affairs lasted for 40,000
or 50,000 years. It took 60,000 years before the ocean recovered
and the sediments appeared normal again.
In a paper published last year in the journal Science,
Zachos' team concluded that only a massive release of carbon
dioxide could have caused both extreme warming and acidification
of ocean waters.
Zachos estimated that 4.5 trillion tons of carbon entered
the atmosphere to trigger the event.
It could take modern civilization just 300 years to unleash
the same quantity of carbon, according to a variety of projections
"This will be a much greater shock," Zachos said.
"The change in modern surface ocean pH will be much
more extreme than it was 55 million years ago."
Times staff writer Kenneth R. Weiss contributed to this