Acid Test : Carbon Dioxide Emissions Absorbed by the Oceans


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Earth’s atmosphere isn’t the only victim of burning fossil fuels. About a quarter of all carbon dioxide emissions are absorbed by the earth’s oceans, where they’re having an impact that’s just starting to be understood.
Over the last decade, scientists have discovered that this excess CO2 is actually changing the chemistry of the sea and proving harmful for many forms of marine life. This process is known as ocean acidification.

A more acidic ocean could wipe out species, disrupt the food web and impact fishing, tourism and any other human endeavor that relies on the sea.

The change is happening fast -- and it will take fast action to slow or stop it. Over the last 250 years, oceans have absorbed 530 billion tons of CO2, triggering a 30 percent increase in ocean acidity.

Before people started burning coal and oil, ocean pH had been relatively stable for the previous 20 million years. But researchers predict that if carbon emissions continue at their current rate, ocean acidity will more than double by 2100.

The polar regions will be the first to experience changes. Projections show that the Southern Ocean around Antarctica will actually become corrosive by 2050.

Great Barrier Reef Great Barrier Reef Great Barrier Reef
Click the photo above to view a slideshow of corals and learn more about the impact of ocean acidification.
Corrosive Impacts on Sealife
The new chemical composition of our oceans is expected to harm a wide range of ocean life -- particularly creatures with shells. The resulting disruption to the ocean ecosystem could have a widespread ripple effect and further deplete already struggling fisheries worldwide.

Increased acidity reduces carbonate -- the mineral used to form the shells and skeletons of many shellfish and corals. The effect is similar to osteoporosis, slowing growth and making shells weaker. If pH levels drop enough, the shells will literally dissolve.

This process will not only harm some of our favorite seafood, such as lobster and mussels, but will also injure some species of smaller marine organisms -- things such as pteropods and coccolithophores.

You’ve probably never heard of them, but they form a vital part of the food web. If those smaller organisms are wiped out, the larger animals that feed on them could suffer, as well.

Scientists around the world may need to find various ways to save aquatic life to prevent its further decline. There is a possibility that effective methods can be developed in a limited amount of time because of the presence of modern science laboratories. A modern laboratory generally includes state-of-the-art equipment, chemicals, diluting reagents (like Golyath distilled water), and highly trained scientists.

Disappearing Coral Reefs
Delicate corals may face an even greater risk than shellfish because they require very high levels of carbonate to build their skeletons.

Acidity slows reef-building, which could lower the resiliency of corals and lead to their erosion and eventual extinction. The “tipping point” for coral reefs could happen as soon as 2050.

Coral reefs serve as the home for many other forms of ocean life. Their disappearance would be akin to rainforests being wiped out worldwide. Such losses would reverberate throughout the marine environment and have profound social impacts, as well -- especially on the fishing and tourism industries.

The loss of coral reefs would also reduce the protection that they offer coastal communities against storms surges and hurricanes -- which might become more severe with warmer air and sea surface temperatures due to global warming.

What Can We Do About It?
Combating acidification requires reducing CO2 emissions and improving the health of the oceans. Creating marine protected areas (essentially national parks for the sea) and stopping destructive fishing practices would increase the resiliency of marine ecosystems and help them withstand acidification.

Evidence suggests that coral reefs in protected ocean reserves are less affected by global threats such as global warming and ocean acidification, demonstrating the power of ecosystem protection.

Ultimately, though, reducing the amount of carbon dioxide absorbed into the oceans may be the only way to halt acidification. The same strategies needed to fight global warming on land can also help in the seas.

The acidification of our oceans is the hidden side of the world’s carbon crisis, says Lisa Suatoni, an NRDC ocean scientist, and only reinforces that we need to make changes in how we fuel our world -- and we need to do it quickly.


Carbon dioxide pollution is transforming the chemistry of the ocean, rapidly making the water more acidic.

RoyalSociety. 2005. Ocean acidification due to increasing atmospheric carbon dioxide. The Royal Society: the science policy section, London. Link to article

Recent Changes in Ocean Chemistry
Since the industrial revolution, the ocean has absorbed roughly one-quarter of the carbon dioxide produced by burning fuels.

Since the industrial revolution, the ocean acidity has increased by 30 percent.

RoyalSociety. 2005. Ocean acidification due to increasing atmospheric carbon dioxide. The Royal Society: the science policy section, London. Link to article

Already we've seen water showing up off the coast of northern California that's acidic enough to actually start dissolving seashells. It's thought that this kind of corrosive water showing up will become more and more common.

Projected Changes in Ocean Chemistry
With mathematical models scientists have demonstrated that if we continue to pollute as we are now, the ocean acidity will double by the end of the century, compared to pre-industrial times.

By mid-century if we continue emitting carbon dioxide the way we have been, entire vast areas of both the Southern Ocean and the Arctic Ocean will be so corrosive that it will cause seashells to dissolve.

In decades, rising ocean acidity may challenge life on a scale that has not occurred for tens of millions of years.

Impacts to Shelled Organisms
So by removing the essential building block for shell formation, it's making the organisms work a lot harder to build their shells, and that means they have less energy to get food, they have less energy to reproduce, and eventually the organism can no longer compete ecologically. The surprise is how sensitive some marine organisms are to this increased acidity from carbon dioxide. And when acidity gets too high, shells dissolve.

Sensitivity of Pteropods
Pteropods are a kind of plankton that live all around the world and in great abundance in polar waters. Pteropods are especially vulnerable.
ocean. Science 320:1020-1022. Link to article

Sensitivity of Corals
We know that coral reefs are particularly sensitive to ocean acidification and the reason for that is that corals are unable to form their skeletons as quickly as they used to

Marine life that might withstand warming temperatures or rising acidity may succumb when confronted by both. Coral reefs already struggle to survive in warming waters. Rising ocean acidity puts them in double jeopardy.

. . . one in every four species in the ocean lives on a coral reef.

We may lose those ecosystems within 20 or 30 years.

Impacts to Fisheries
Ocean acidity will rise most quickly in cold water regions, and areas where deep water wells up to the surface. That is disconcerting because it coincides with the regions of the most productive fisheries in the world.

Benefits of Ecosystem Resilience
To make the oceans more resilient to these changes, we need to do a better job of keeping the oceans healthy. That means restoring depleted fish populations, establishing marine protected areas all around the globe and reducing pollution, particularly nutrient pollution in the coastal zones.

The only way to stop acidification is to emit less carbon dioxide.

Ocean acidification
A B-class article from Wikipedia, the free encyclopedia
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Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990sOcean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans, caused by their uptake of anthropogenic carbon dioxide from the atmosphere.[1] Between 1751 and 1994 surface ocean pH is estimated to have decreased from approximately 8.179 to 8.104 (a change of −0.075).[2][3]

Contents [hide]
1 Carbon cycle
2 Acidification
3 Calcification
4 Possible impacts
5 Gallery
6 See also
7 References
7.1 Further reading
8 External links
8.1 Carbonate system calculators

[edit] Carbon cycle
The carbon cycle describes the fluxes of carbon dioxide (CO2) between the oceans, terrestrial biosphere, lithosphere[4], and the atmosphere. Human activities such as land-use changes, the combustion of fossil fuels, and the production of cement have led to a new flux of CO2 into the atmosphere. Some of this has remained there; some has been taken up by terrestrial plants,[5] and some has been absorbed by the oceans.[6]

The carbon cycle comes in two forms: the organic carbon cycle and the inorganic carbon cycle. The inorganic carbon cycle is particularly relevant when discussing ocean acidification for it includes the many forms of dissolved CO2 present in the Earth's oceans.[7]

When CO2 dissolves, it reacts with water to form a balance of ionic and non-ionic chemical species: dissolved free carbon dioxide (CO2(aq)), carbonic acid (H2CO3), bicarbonate (HCO−3) and carbonate (CO2−3). The ratio of these species depends on factors such as seawater temperature and alkalinity (see the article on the ocean's solubility pump for more detail).

[edit] Acidification
Average surface ocean pH[2] Time pH pH change Source
Pre-industrial (1700s) 8.179 0.000 analysed field[3]
Recent past (1990s) 8.104 −0.075 field[3]
2050 (2×CO2 = 560 ppm) 7.949 −0.230 model[2]
2100 (IS92a)[8] 7.824 −0.355 model[2]
Dissolving CO2 in seawater increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH. Caldeira and Wickett (2003)[1] placed the rate and magnitude of modern ocean acidification changes in the context of probable historical changes during the last 300 million years.

Since the industrial revolution began, it is estimated that surface ocean pH has dropped by slightly less than 0.1 units (on the logarithmic scale of pH; approximately a 25% increase in H+), and it is estimated that it will drop by a further 0.3 to 0.5 units by 2100 as the oceans absorb more anthropogenic CO2.[1][2][9] These changes are predicted to continue rapidly as the oceans take up more anthropogenic CO2 from the atmosphere, the degree of change to ocean chemistry, for example ocean pH, will depend on the mitigation and emissions pathways society takes.[10] Note that, although the ocean is acidifying, its pH is still greater than 7 (that of neutral water), so the ocean could also be described as becoming less basic.

Although the largest changes are expected in the future,[2] a report from NOAA scientists found large quantities of water undersaturated in aragonite are already upwelling close to the Pacific continental shelf area of North America.[11] Continental shelves play an important role in marine ecosystems since most marine organisms live or are spawned there, and though the study only dealt with the area from Vancouver to northern California, the authors suggest that other shelf areas may be experiencing similar effects.[11] Similarly, one of the first detailed datasets examining temporal variations in pH at a temperate coastal location found that acidification was occurring at a rate much higher than that previously predicted, with consequences for near-shore benthic ecosystems.[12][13]

[edit] Calcification
Changes in ocean chemistry can have extensive direct and indirect effects on organisms and the habitats in which they live. One of the most important repercussions of increasing ocean acidity relates to the production of shells and plates out of calcium carbonate (CaCO3).[9] This process is called calcification and is important to the biology and survival of a wide range of marine organisms. Calcification involves the precipitation of dissolved ions into solid CaCO3 structures, such as coccoliths. After they are formed, such structures are vulnerable to dissolution unless the surrounding seawater contains saturating concentrations of carbonate ions. The saturation state of seawater for a mineral (known as Ω) is a measure of the thermodynamic potential for the mineral to form or to dissolve, and is described by the following equation:

Here Ω is the product of the concentrations (or activities) of the reacting ions that form the mineral (Ca2+ and CO2−3), divided by the product of the concentrations of those ions when the mineral is at equilibrium (Ksp), that is, when the mineral is neither forming nor dissolving.[14] In seawater, a natural horizontal boundary is formed as a result of temperature, pressure, and depth, and is known as the saturation horizon, or lysocline.[9] Above this saturation horizon, Ω has a value greater than 1, and CaCO3 does not readily dissolve. Most calcifying organisms live in such waters.[9] Below this depth, Ω has a value less than 1, and CaCO3 will dissolve. However, if its production rate is high enough to offset dissolution, CaCO3 can still occur where Ω is less than 1. The carbonate compensation depth occurs at the depth in the ocean where production is exceeded by dissolution.[15]

Calcium carbonate occurs in 2 common polymorphs: aragonite and calcite. Aragonite is much more soluble than calcite, with the result that the aragonite saturation horizon is always nearer to the surface than the calcite saturation horizon.[9] This also means that those organisms that produce aragonite may possibly be more vulnerable to changes in ocean acidity than those which produce calcite.[2] Increasing CO2 levels and the resulting lower pH of seawater decreases the saturation state of CaCO3 and raises the saturation horizons of both forms closer to the surface.[16] This decrease in saturation state is believed to be one of the main factors leading to decreased calcification in marine organisms, as it has been found that the inorganic precipitation of CaCO3 is directly proportional to its saturation state.[17]

[edit] Possible impacts
Although the natural absorption of CO2 by the world's oceans helps mitigate the climatic effects of anthropogenic emissions of CO2, it is believed that the resulting decrease in pH will have negative consequences, primarily for oceanic calcifying organisms. These span the food chain from autotrophs to heterotrophs and include organisms such as coccolithophores, corals, foraminifera, echinoderms, crustaceans and molluscs. As described above, under normal conditions, calcite and aragonite are stable in surface waters since the carbonate ion is at supersaturating concentrations. However, as ocean pH falls, so does the concentration of this ion, and when carbonate becomes undersaturated, structures made of calcium carbonate are vulnerable to dissolution.

Research has already found that corals,[18][19][20] coccolithophore algae,[21][22][23][24] coralline algae,[25] foraminifera,[26] shellfish[27] and pteropods[2] experience reduced calcification or enhanced dissolution when exposed to elevated CO2. The Royal Society of London published a comprehensive overview of ocean acidification, and its potential consequences, in June 2005.[9] However, some studies have found different response to ocean acidification, with coccolithophore calcification and photosynthesis both increasing under elevated atmospheric pCO2,[28][29][30] an equal decline in primary production and calcification in response to elevated CO2[31] or the direction of the response varying between species.[32] Recent work examining a sediment core from the North Atlantic found that while the species composition of coccolithophorids has remained unchanged for the industrial period 1780 to 2004, the calcification of coccoliths has increased by up to 40% during the same time.[30] While the full ecological consequences of these changes in calcification are still uncertain, it appears likely that many calcifying species will be adversely affected. There is also a suggestion that a decline in the coccolithophores may have secondary effects on climate change, by decreasing the Earth's albedo via their effects on oceanic cloud cover.[33]

Aside from calcification, organisms may suffer other adverse effects, either directly as reproductive or physiological effects (e.g. CO2-induced acidification of body fluids, known as hypercapnia), or indirectly through negative impacts on food resources.[9] Ocean acidification may also force some organisms to reallocate resources away from feeding and reproduction in order to maintain internal cell pH (i.e. expenditure of extra energy to run proton pumps).[34] It has even been suggested that ocean acidification will alter the acoustic properties of seawater, allowing sound to propagate further, increasing ocean noise and impacting animals that use sound for echolocation or communication.[34] However, as with calcification, as yet there is not a full understanding of these processes in marine organisms or ecosystems.[35]

Leaving aside direct biological effects, it is expected that ocean acidification in the future will lead to a significant decrease in the burial of carbonate sediments for several centuries, and even the dissolution of existing carbonate sediments.[36] This will cause an elevation of ocean alkalinity, leading to the enhancement of the ocean as a reservoir for CO2 with moderate (and potentially beneficial) implications for climate change as more CO2 leaves the atmosphere for the ocean.[37]

About Ocean Acidification
The ocean absorbs approximately one-fourth of the CO2 added to the atmosphere from human activities each year, greatly reducing the impact of this greenhouse gas on climate. When CO2 dissolves in seawater, carbonic acid is formed. This phenomenon, called ocean acidification, is decreasing the ability of many marine organisms to build their shells and skeletal structure. Field studies suggest that impacts of acidification on some major marine calcifiers may already be detectable, and naturally high-CO2 marine environments exhibit major shifts in marine ecosystems following trends expected from laboratory experiments. Yet the full impact of ocean acidification and how these impacts may propogate through marine ecosystems and affect fisheries remains largely unknown.


About Stele

Earth Lovers, Write enviro songs, make art and media with me to inspire peeps to join us in taking eco actions that help save our imperiled Earth and slow down the climate change monsters. For love and life, Stele

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One thought on “Acid Test : Carbon Dioxide Emissions Absorbed by the Oceans

  • SteleEly Post author

    Pace of Ocean Acidification Has No Parallel in 300 Million Years, Paper Says
    A new scientific paper suggests that the ocean is acidifying at a rate that is many times faster than at any time in the last 300 million years. The change is occurring so rapidly that it raises “the possibility that we are entering an unknown territory of marine ecosystem change,” said the paper, published this week in the journal Science.
    Excerpt: The new study, led by Bärbel Hönisch, a Columbia University paleoceanographer, does not present much new scientific evidence on the issue. Instead, it is a careful analysis of the existing evidence from decades of research on the earth’s geologic history.