Oceans Passing Critical CO2 Threshold
UXBRIDGE, Canada - An apparent
rapid upswing in ocean acidity in recent years is wiping out coastal
species like mussels, a new study has found.
dramatic changes," said Timothy Wootton of the Department of Ecology
and Evolution at the University of Chicago, lead author of the study
published Monday in the Proceedings of the National Academy of
Sciences. The study shows increases in ocean acidity that are more than
10 times faster than any prediction.
"It appears that we've crossed a threshold where the ocean can
no longer buffer the effects of CO2 in the atmosphere," Wootton told
For millions of years, the levels of carbon dioxide in the
atmosphere and the ocean were in balance, but the burning of fossil
fuels and deforestation has put more CO2 into the atmosphere over the
last 150 years. The oceans have absorbed one-third -- about 130 billion
tonnes -- of those human emissions and have become 30 percent more
acidic as the extra CO2 combines with carbonate ions in seawater,
forming carbonic acid.
Each day, the oceans absorb 30 million tonnes of CO2,
gradually and inevitably increasing their acidity. There is no
controversy about this basic chemistry; however, there is disagreement
about the rate at which the oceans are becoming acidic and the
The ocean's pH -- the measure of acidity or alkalinity -- has
been declining, or becoming more acidic, at a rate of about 0.02 per
decade since 1980, said Ulf Riebesell, a biological oceanographer at
the Leibniz Institute of Marine Sciences in Kiel, Germany.
"We're just starting to realise the far-reaching impacts of
ocean acidification," Riebesell told IPS, noting that the term ocean
acidification was coined just four years ago.
Wootton and colleagues measured a massive pH decline of 0.4
units in just eight years off the northwest tip of Washington State in
the U.S. And that abrupt increase has had a major impact on marine
species in the tide pool on Tatoosh Island where the study was
"Large shell species like mussels and goose barnacles were dying at a faster rate and being replaced by other species," he said.
Increased seawater acidity means there is less calcium
carbonate in the water for corals and shell-forming species like
mussels and phytoplankton to grow or maintain their skeletons. The once
verdant mussel beds in the study area were being replaced by algae,
"We are not exactly certain why the mussels declined but
preliminary evidence has shown some thinning of shells on snails in the
area," he told IPS.
Wootton also cautions that the results are just from one area,
but said there have been other regions where large increases in the
rate of ocean acidity have been measured along the entire west coast of
North America. However, none have been as large or consistent as those
at Tatoosh Island.
"We measured even greater increases in acidity this summer," he said. "I'm really getting worried now."
Riebesell and other ocean acidification experts contacted by
IPS say atmospheric CO2 could not be responsible for the large increase
Wootton measured. Either their methodology is flawed or there is some
local anomaly that is skewing the results, they said.
"If the pH change is real...a likely explanation would be that
also other factors related to seawater pH have changed over the
eight-year period in the tidal pool," said Riebesell.
Wootton told IPS they looked for other causes of both the
declines in mussels and other species and the high acidity levels. They
could find no other explanation.
Ocean acidification is a very new field of science and the
best ways to do research are still being investigated. In fact, the
Leibniz Institute of Marine Sciences was host to an international
workshop on that very topic last week, said Riebesell. A draft outline
of a guide for Best Practices in Ocean Acidification Research and Data
Reporting will be forthcoming.
This dispute aside, marine scientists are very worried about
ocean acidification and the potential to decimate corals and a large
number other species. Some have suggested that little will be left in
the oceans except bacteria, jellyfish and algae without major
reductions in emissions of fossil fuels and an end to deforestation.
"CO2 is making the oceans very sick," said Jackie Savitz,
senior campaign director for Oceana's Pollution Campaigns. Oceana is an
international ocean conservation group.
"There is a strong likelihood of a massive extinction of corals by mid-century," Savitz said in an interview.
To prevent this, atmospheric CO2 concentrations need to return
to 350 parts per million, the pre-industrial level, she said. Currently
CO2 is 385 ppm and growing at 2 to 3 ppm annually. The
Intergovernmental Panel on Climate Change, European Union and others
have called for a climate stabilisation of 450 ppm to ward off the
worst affects of climate change.
"Four hundred and fifty ppm is not going to save corals," she
said, because the acidification of the ocean would kill and weaken
corals and other species that make up the reef ecosystems. "We need to
stop using fossil fuels period. Carbon that's in the ground now should
Some leading climates scientists agree.
In study published last week, 10 prominent scientists said that
the level of globe-warming carbon dioxide in the air has probably
already reached a point where world climate will change disastrously
unless the level can be reduced to 350 ppm. The study is a departure
from recent estimates that truly dangerous levels would be reached only
later in this century.
Climate feedbacks have already begun, particularly at the
poles, accelerating the warming of the planet, said lead author James
E. Hansen, director of the Goddard Institute for Space Studies, part of
Columbia University's Earth Institute.
Ocean acidification is scary, acknowledges Riebesell.
Acidification cannot be fixed quickly. It might take a thousand years
for the oceans to regain their buffering capacity to prevent continuing
acidification. Many species will not be able to adapt and there will be
no place to hide, he said.
"The oceans will be very different in 20 years," he warned.