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Study Finds Rate of Ocean Acidification Faster than Expected

University of Chicago scientists have found that the ocean is growing more acidic faster than previously thought. In addition, they have found that the increasing acidity correlates with increasing levels of atmospheric carbon dioxide, according to a paper published online by the Proceedings of the National Academy of Sciences on 24 November.

The new study is based on 24,519 measurements of ocean pH spanning eight years, which represents the first detailed dataset on variations of coastal pH at a temperate latitude—where the world’s most productive fisheries live.

The ocean plays a significant role in global carbon cycles. When atmospheric carbon dioxide dissolves in water it forms carbonic acid, increasing the acidity of the ocean. During the day, carbon dioxide levels in the ocean fall because photosynthesis takes it out of the water, but at night, levels increase again. The study documented this daily pattern, as well as a steady increase in acidity over time.

The increasingly acidic water harms certain sea animals and could reduce the ocean’s ability to absorb carbon dioxide, the authors said. Scientists have long predicted that higher levels of atmospheric carbon dioxide would make the ocean more acidic. Nevertheless, empirical evidence of growing acidity has been limited.

The acidity increased more than 10 times faster than had been predicted by climate change models and other studies. This increase will have a severe impact on marine food webs and suggests that ocean acidification may be a more urgent issue than previously thought, at least in some areas of the ocean.

—J. Timothy Wootton

Conducted at Tatoosh Island in the Pacific Ocean off the coast of Washington, the study documented that the number of mussels and stalked barnacles fell as acidity increased. At the same time, populations of smaller, shelled species and noncalcareous algae increased.

Models revealed strong links between the dynamics of species living on the shore and variation in ocean pH. The models project substantial shifts in the species dominating the habitat as a consequence of both the direct effects of reduced calcification and indirect effects arising from the web of species interactions.

—J. Timothy Wootton


  • J. Timothy Wootton, Catherine A. Pfister, and James D. Forester (2008) Dynamic patterns and ecological impacts of declining ocean pH in a high-resolution multi-year dataset. PNAS, doi: 10.1073/pnas.0810079105



Interesting to note the paper's conclusion demonstrates a growth shift from mussels and stalked barnacles species to populations of smaller, shelled species and noncalcareous algae - as alkalinity drops. This suggests a natural (balancing) adjustment of marine species to changing ocean chemistry.

In another interesting paper the calcereous Scleractinian coral was shown to survive well an increase in ocean acidification:

"This study demonstrates that skeleton-producing corals grown in acidified experimental conditions are able to sustain basic life functions, including reproductive ability, in a sea anemone-like form and will resume skeleton building when reintroduced to normal modern marine conditions. " Fine and Tchernov

Science 30 March 2007:
Vol. 315. no. 5820, p. 1811


It is not then necessary to still use petrol to propel cars and trucks if it pollute the air and water in oceans. Then gm with their volt and toyota with their gasoline prius are not offering good alternative cars. Only honda offer an alternative with their fcx clarity but they only built 200 unit a years.. and they still give the infrastructure problem to their customers to find a hydrogen dispensing machine and there is almost no hydrogen stations, LOL. they kill themself their unfinnish product. They at least can put a water electrolyser inside the clarity so the customer will have not to rely to the hydrogen station.

Why should I have to pay to read on line a study performed at government expense?

From the abstract, “in some areas”

From the article, “When atmospheric carbon dioxide dissolves in water it forms carbonic acid, increasing the acidity of the ocean.”

This is not true. Carbon dioxide dissolves in water it forms carbonic acid in 'fresh' water. The ocean is not fresh water. The ocean is an alkaline system.


I wonder how these ancient calcaerous organisms survived the episodes in the recent past (40 million years ago) when CO2 was many times what it is today? I don't dispute the concern over changing ocean ecology. But I wonder if anyone has looked at fossil coral reefs and coral-lated this with the CO2 concs at the time.

Bike Commuter Dude

coral-lated.... nice

There are events in geological history where sharp rises in temperature appear to be initiated as well as driven high by very large spikes in greenhouse gases not unlike what fossil fuel emissions are on the way to being today. The Paleocene Eocene Thermal Maximum is such a case. Roughly 55 million years ago, ocean pH levels dropped drastically and global temperatures rapidly rose over 5oC. The resolution of proxy records that are available indicate that this happened in a period of time no longer than 5K years, but it is not possible to know if it happened even faster. The likely cause of this event was massive releases of methane from the ocean floors, perhaps due to some smaller warming or changes in sea level. It took over 100K years for the ocean, atmosphere and temperatures to return to their previous state. The result was a mass extinction event that took millions of years to recover from.-


Interesting idea. But how does the AGW attributed 0.8C temperature rise over the last 100 years equate to your 50.0 C temperature rise over 5K years??

The cause of the PETM is very poorly understood. Various causes in your link point to possible events including massive volcanic activity, comet impact, peat burning, orbital forcing, and methane release. There is far too little data to reach a positive conclusion.

To analogize PETM to the current paltry AGW attributed rise is disingenuous at best.


get real,
Anon - "rapidly rose over 5oC."

$reel - "to your 50.0 C temperature rise over 5K years??"
only an order of magnitude out.

the calcareous forming ability is reported in other studies as equally applicable to vertebrate fishes as hard shelled.
Some new studies are investigating a(very recent) explosion in jellyfish numbers and aim to se if this is a trend. They hope to investigate the possibility of these short lived organisms taking substantial carbon to the ocean floor as a natural sequestration.


I wrote 5oC, not 50C. "o" means degrees. And the only reason I gave the link was to answer the question of what Ocean Acidification does to change ocean ecologies.

richard schumacher

The point, "reel$$", is that we're already nearly one-fifth of the way to a mass extinction event. But as long as you can still eat shellfish before you die, who cares what happens after, eh?



20% mass extinction? Citation please? And apparently the research shows both corals and shellfish species surviving well in a lower alkaline ocean.

"Exaggeration leads the coalition of disbelief."

Paul F. Dietz

I wonder how these ancient calcaerous organisms survived the episodes in the recent past (40 million years ago) when CO2 was many times what it is today?

It is my understanding that ocean pH will be buffered by dissolution of calcium carbonate. However, this process goes at a limited rate, so if the CO2 concentration rises very rapidly (as it is doing now) it can't keep up. Those episodes in the geologic past very likely involved much slower changes.


Taken from another perspective, oceanic CO2 levels rising more rapidly than expected means the ocean is absorbing more CO2 than expected, reducing the amount of atmospheric CO2 more than expected.

Given that climates are big complicated things and given that we seem to read about things that are surprises or unexpected on a pretty regular basis, how can we be so sure that our climate models (which depend on huge assumptions, like ocean CO2 uptake rates) are even remotely useful?

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