Comprehensive study makes key findings of ocean pH variations

Dec 22, 2011

A group of 19 scientists from five research organizations have conducted the broadest field study of ocean acidification to date using sensors developed at Scripps Institution of Oceanography, UC San Diego.

The study, "High-Frequency Dynamics of Ocean pH: A Multi-Ecosystem Comparison," is reported in the Dec. 19 issue of the journal . It is an important step toward understanding how specific ecosystems are responding to the change in seawater chemistry that is being caused as the oceans take up extra carbon dioxide produced by human greenhouse gas emissions, said its authors.

"These data represent a critical step in understanding the consequences of ocean change: the linkage of present-day pH exposures to organismal tolerance and how this translates into in ," the authors wrote. "These pH time series create a compelling argument for the collection of more continuous data of this kind."

research is a relatively new study topic as scientists have only appreciated the potential extent of acidification within the last decade. As greenhouse gas emissions have accelerated in the past century, the oceans have taken up about a third of the carbon dioxide produced by human activities. That excess beyond natural levels increases amounts of carbonic acid in seawater. Acidification also limits the amount of carbonate forms that are needed by marine invertebrates such as coral and shelled organisms to form their skeletons.

Though many lab simulations of this effect have been performed recently, including at a new acidification laboratory in development at Scripps, there have been few comparable field studies. Using sensors recently developed at Scripps, the researchers surveyed marine ecosystems ranging from in the to volcanic CO2 vent communities in the Mediterranean Sea.

They found that in some places, such as Antarctica and the Line Islands of the south Pacific, the range of pH variance is much more limited than in areas of the California coast subject to large vertical movements of water known as upwellings. In some of their study areas, they found that the decrease in seawater pH being caused by is still within the bounds of natural pH fluctuation. Some areas already experience daily acidity levels that scientists had expected would only be reached at the end of the 21st Century.

This study is important for identifying the complexity of the ocean acidification problem around the globe. Our data show such huge variability in seawater pH both within and across marine ecosystems making global predictions of the impacts of ocean acidification a big challenge. Some ecosystems such as coral reefs experience a daily range in pH that exceeds the predicted increase in pH over the next century. While these data suggest that marine organisms may be more adapted to fluctuations in pH than previously thought much more research is needed to determine how individual species will respond over time. Importantly, these new sensors allow us continuously and autonomously monitor pH from remote parts of the world and thus provide us with important baselines from which we can monitor future changes caused by ocean acidification.

Because many in the marine chemistry community have expressed concerns that ocean acidification could happen too rapidly for some organisms to adapt, the researchers said that this finding is an important step toward identifying the mechanisms some marine organisms have developed in order to cope. They also said that knowledge of actual pH ranges in various ecosystems should improve assumptions about future pH levels that can only rely on broad generalizations about seawater chemistry. Furthermore it could guide future lab and field studies that investigate the limits of resistance and resilience in various marine communities.

The researchers used "SeaFET" sensors developed at Scripps by marine chemistry researcher Todd Martz. The sensors can measure pH and temperature in the top 70 meters (230 feet) of the ocean. Since 2009, Martz's team has constructed 52 SeaFETs, which have been used by 13 different research groups to study individual ecosystems.

"This collaboration was not planned; it just naturally formed as several of my colleagues requested replicates of a pH sensor that I built while working as a postdoc in Ken Johnson's group at MBARI," said Martz. "When I arrived at Scripps, we re-engineered my prototype design and since then I have not been able to keep up with all of the requests for sensors. Because every sensor used in this study was built at Scripps, I was in a unique position to assimilate a number of datasets, collected independently by researchers that otherwise would not have been in communication with each other. Each time someone deployed a sensor, they would send me the data and eventually it became clear that a synthesis should be done to cross-compare this diverse collection of measurements."

Deployed in the ocean over the course of months or years, the sensors are also able to record important data about how pH fluctuates over time. As data accumulates, the researchers suggested that the field data could identify ocean regions especially vulnerable to the effects of ocean acidification or areas that provide natural protections to organisms at risk.

"Such knowledge could enable protection, management, and remediation of critical marine habitats and populations in the future," wrote the authors.

Despite surveying 15 different ocean regions, the authors noted that they only made observations on coastal surface oceans and that more study is needed in deeper ocean regions farther away from land. Martz noted that large-scale programs like Argo, in which a network of more than 3,000 floats distributed throughout the oceans, measure fundamental data.

"The Honeywell DuraFET pH sensor used in the SeaFET has been a great tool for characterizing shallow sites from moorings and for use in shipboard underway systems," Martz said. "The next challenge will be observing the pH of the entire ocean from top to bottom without using ships. I am really excited about the prospect of adding these sensors to mobile autonomous platforms like profiling floats, gliders, and drifters. In fact we continue to work with Ken Johnson and MBARI to make this a reality. I think you can expect to see a pH sensor sending back data from an Argo-type profiling float at some point in 2012."

Explore further: Global CO2 emissions increase to new all-time record, but growth is slowing down

Related Stories

Increased acidity not an even test for coral reefs

Nov 10, 2011

Coral reefs can both positively and negatively influence the acidity of their surrounding seawater. That is the take-home message of two papers recently published in the international journal Global Change Bi ...

Ecosystems under threat from ocean acidification

Mar 29, 2010

Acidification of the oceans as a result of increasing levels of atmospheric carbon dioxide could have significant effects on marine ecosystems, according to Michael Maguire presenting at the Society for General Microbiology's ...

Recommended for you

New York state bans fracking

5 minutes ago

Governor Andrew Cuomo said Wednesday he would ban hydraulic fracking in New York State, citing health concerns about the controversial oil and gas drilling technique.

User comments : 10

Adjust slider to filter visible comments by rank

Display comments: newest first

A_Paradox
1 / 5 (1) Dec 22, 2011
Firstly:
Acidification also limits the amount of carbonate forms that are needed by marine invertebrates such as coral and shelled organisms to form their skeletons.


I think that should be "Acidification also limits the availability of forms of carbonate that are needed by marine organisms ...."

Secondly:
If it really is the case that the acidity of ocean water fluctuates relatively widely from whatever is the average, that may well be a good thing because presumably marine species are adapted to this. On the other hand, as with climate and weather, it may turn out that the clear net increase of CO2 in the ocean forces an increase in the range of the fluctuations, ie delta pH, and in the frequencies, and durations of non average pH.

So, similarly to the way global warming maybe giving us less climate and more weather, acidification may be giving fish and seaweed less predictable ambiance and more stress to homeostasis.
GSwift7
3 / 5 (4) Dec 22, 2011
A_Paradox:

So, similarly to the way global warming maybe giving us less climate and more weather, acidification may be giving fish and seaweed less predictable ambiance and more stress to homeostasis


I call BS. You just made that up out out of thin air (no co2 pun intended).

The conclusion I draw from this is that it isn't time to draw any conclusion yet. This is an example of how little they knew, but people were eager to propose doom and gloom theories and predictions anyway.

I suspected something like this for a long time. Especially in a choral reef environment. From daytime to nighttime and in between, the whole reef goes through a daily cycle of transformation, similar to a flower garden in your yard. Organisms take up and release chemicals, wind and rain have daily cycles in the tropics, etc. I don't find it surprising to see a large daily change in Ph.

I don't think that says anything about how AGW is effecting it.
GSwift7
1 / 5 (1) Dec 22, 2011
Also:

Your statement about GW causing some increase in 'weather' is wrong according to NOAA and every other top source. Can I ask what your reference for that was? The following is from the NOAA FAQ page:

Does "global warming" cause tornadoes? No. Thunderstorms do. The harder question may be, "Will climate change influence tornado occurrence?" The best answer is: We don't know. According to the National Science and Technology Council's Scientific Assessment on Climate Change, "Trends in other extreme weather events that occur at small spatial scales--such as tornadoes, hail, lightning, and dust storms--cannot be determined at the present time due to insufficient evidence."


http://www.spc.no...matology

I can provide other good sources to confirm.
GSwift7
1 / 5 (1) Dec 22, 2011
darn, it's hard to get recently updated faq sections. Here's one from the National Hurricane Center. They have a section titled "Consensus Statements by International Workshop on Tropical Cyclones-VI"

It states:
Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point


source: http://www.aoml.n.../G3.html

More recent studies and statements from NOAA are more confident that evidence of a link does not yet exist in our records.
gregor1
1 / 5 (3) Dec 22, 2011

@GSwift7

"Especially in a choral reef environment."

I love this idea. The Idea of all the organisms singing in a choir is quite lovely and well in tune with the spirit off cchristmas
omatumr
1 / 5 (4) Dec 23, 2011
Before switching the topic of discussion from AGW to ocean pH, the public deserves a government response to growing evidence that global economies and global temperatures have been manipulated:

http://strata-sph...es/17772

www.stansberryres...sue.html

http://chiefio.wo...ber-2011
rubberman
not rated yet Dec 23, 2011
It's always nice to hear that species are more adept at dealing with change than we initially assumed, especially in the ocean. Hopefully they find similar results with the organisms that constitute the base of the ocean food chain.
omatumr
1.3 / 5 (4) Dec 23, 2011
Below is a Christmas message of Hope for everyone facing the economic turmoils and fears that Al Gore, the UN, and world leaders have been promoting:

http://dl.dropbox...Fear.pdf

That same message was posted on leading climate blogs:

http://judithcurr...t-152465

Together with a reminder that world leaders are actually totally powerless over the forces of nature:

http://judithcurr...t-152555

Or as my late brother-in-law might have said,

"Big Brother's Butt!"

Best wishes for the Holidays and the New Year!

Today all is well,
Oliver K. Manuel
Skepticus_Rex
2.7 / 5 (3) Dec 27, 2011
In some of their study areas, they found that the decrease in seawater pH being caused by greenhouse gas emissions is still within the bounds of natural pH fluctuation.


Whoops! Like I said in the comments section of another article elsewhere on the site, there are some interesting things coming around the corner regarding ocean pH. :)

The interesting thing about this study is the fact that 'acidification' in a number of areas still is within natural fluctuation, depending upon the area sampled. This has considerable ramifications for such claims of 'ocean acidification' for the foreseeable future. Fear-mongering is not of any use but longer-term studies definitely are needed over the next decades.

There will be even more than is told by even this story that will be revealed over time. Wait and watch for it as the data becomes more available to more people... :)
tadchem
not rated yet Dec 27, 2011
A little wet chemistry is due: The CO2/H2O <-> H2CO3 <-> HCO3- <-> CO3= equilibrium shift almost instantaneously as CO2 is added (on the left). The pH determines the final concentration of all of these forms. CO2 is part of this 'bicarbonate buffer system' that actually mitigates pH excursions.
The form usable by marine life is HCO3- (bicarbonate) and is the predominant form in the pH range of 6.37 to 10.36, with 90% of the carbon dioxide tied up as bicarbonate as long as the pH is between about 7.3 and 9.3. The 'acidification' of the oceans that everyone seems to fret over is actually 'de-alkalization', and the pH only seems to drop below 7.0 around sulfur-releasing volcanic vents on the sea floor.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.