Ocean Acidification: Global warming's 'evil twin'
By PAT GARBER
Coastal Review Online
Ocracoke Working Watermen's Association earlier
this month hosted a training session for a project to monitor baby
oysters, or spat. Students and volunteers will be trained to collect
and count oyster offspring. The project, sponsored by North
Carolina Sea Grant, is part of a larger effort to understand
why North Carolina's oyster population is in decline.
on the other side of the country, scientists have puzzled over why the
entire batch of 100 million free-swimming baby oysters at Whiskey Creek
Shellfish Hatchery in coastal Oregon have died. The
that they reached is alarming, at the least. The struggling larvae were
unable to form their protective shells because of highly acidic pH
levels in the ocean. High acid levels decrease carbonate ions needed
for shell production.
The acidity is the result of excessive
carbon dioxide, or CO2, in the ocean, absorbed from the Earth's
atmosphere. The CO2 is the by-product of the burning of fossil fuels
--coal and oil, primarily -- which also causes global warming or
In late October, 2012, Hurricane Sandy, later
dubbed a “super-storm,” grabbed headlines and awoke the American public
to the reality of carbon dioxide-induced climate change. Scientists and
climatologists had been trying to raise awareness for years, but it
took a major disaster to make most people accept its imminent presence
Few people are aware even now, however, of what some
scientists call the “evil twin” of global warming; ocean acidification.
This equally serious threat is already showing up in the Pacific Ocean
and polar seas, where the cold, nutrient-rich waters from the deep are
naturally more acidic than surface waters. While the full brunt of
ocean acidification is not expected to hit for decades, it is expected
to affect marine ecosystems globally and might even factor into North
Carolina's oyster decline.
Climate scientists define ocean
acidification as the ongoing decrease in the pH of the Earth's oceans,
caused by the absorption of human-caused carbon dioxide from the
atmosphere. It was once believed that this was a good thing, as it
buffered the full effects of global warming on land. Scientists now
A decrease in pH means an increase in
acidity, which can be catastrophic for ecosystems. Acid rain provides
an illustration. Emissions of sulfur dioxide and nitrogen dioxide from
vehicle exhaust and coal-burning power plants are carried by the wind,
often for hundreds of miles, and deposited as acidic rainwater. It can
peel paint, corrode steel and erode stone buildings and statues. Acid
rain has damaged crops, weakened or killed plants and raised pH levels
in freshwater lakes so high that fish and other aquatic animals have
died. Acidification may be invisible to the eye, but some of upstate
New York's most beautiful lakes are lasting testaments to its deadly
Before people began burning coal and oil, ocean pH
had been relatively stable for 20 million years, according to
scientists at the Natural Resources Defense Council, an advocacy group.
Over the last 250 years, roughly coinciding with the Industrial
Revolution, oceans have absorbed 503 billion tons of CO2, causing a 30
percent increase in ocean acidity. At current rates, ocean acidity is
predicted to more than double by 2100.
could have serious consequences for near-shore, bottom-dwelling
ecosystems and for calcifying organisms such as crustaceans, molluscks
and echinoderms, such as star fish and sand dollars. Corals, which
require very high levels of carbonate, are at even greater risk. Coral
reefs, which provide habitat for one fourth of all marine species,
could at the present rate of acidification be extinct by
Pteropods, a kind of plankton that lives around the world and are a
major part of the marine food chain, are also especially vulnerable.
National Oceanic and Atmospheric Administration has been studying
falling pH in the ocean and its impact on marine ecosystems for three
decades. Its studies have revealed lower reef-building rates in corals,
the loss of protective shells in free-swimming zooplankton and lower
survival rates of larval marine species, including fish and shellfish.
The studies predict that there will be substantial socio-economic
effects, including decimated fisheries and reduced protection against
storm surges as coastal reefs disappear.
study of ocean acidification is a relatively new science, and all the
ramifications are not yet clear. A September 2012 issue of Scientific American
stated that rising CO2 in the oceans affects the mental abilities of
some marine life. It cited impaired ability in clownfish to
discriminate kin and predators and mollusk larvae wandering farther
afield into unsafe waters, making them more susceptible to predation.
Other studies document depressed metabolic rates in jumbo squid and
depressed immune systems in blue mussels.
The Woods Hole
Oceanographic Institute recently conducted a study that revealed
unexpected results. It found that while corrosive carbonic acid (formed
from dissolved CO2) destroys the shells of clams, oysters, scallops and
conchs, CO2 appears to increase the production of calcium carbonate,
needed for shell-building in such crustaceans as lobsters, blue crabs
and prawns. Clearly, scientists are a long way from understanding all
the effects of CO2-saturated oceans.
In late 2012, scientists
from 37 countries met in Monterey, California to discuss these issues.
“The Ocean in a High-CO2 World” symposium looked at possible solutions,
including spreading vast amounts of limestone on the ocean surfaces.
Lime is alkaline and would buffer the acid. The state of Washington
recently established a blue-ribbon panel to come up with a plan to cope
with ocean acidification, the first state to do so. It outlined 42
steps, including adaptation, remediation, monitoring and reduction.
warm coastal waters of North Carolina and other states on the Eastern
Seaboard have not yet shown the effects of rising pH. Nathan Hall, a
researcher at the UNC Institute of Marine Sciences
in Morehead City, said that there are already such huge variations in
acidity due to pollutants and runoff from the land that, while the
long-term effects of ocean acidification are alarming, they are not yet
Ocracoke waterman Gene Ballance, who works
closely with oyster research and restoration, says that he does not
believe acidification has been considered as a cause of oyster decline
in Pamlico Sound. Susan Massengale, a spokeswoman with the
Division of Water Quality, explained that the issue is in the research
stage in North Carolina and that the state is waiting until “the
science catches up with itself.”
Scientists at National
Resources Defense Council, however, think “this change is happening
fast, and it will take fast action to slow or stop it.” All
experts agree that the only definitive solution to ocean acidification
is to reduce the amount of CO2 humans release into the atmosphere.
scientist Lisa Suatoni says that our CO2 emissions “may soon challenge
marine life on a scale not seen for tens of millions of years.”
Oceanographer Jean-Pierre Gatluso predicts that unless the present
trend is interrupted, “the oceans will become hot, sour and
story is provided courtesy of Coastal Review Online, the coastal news
and features service of the N.C. Coastal Federation. You can read other
stories about the N.C. coast at www.nccoast.org.)