Approximately one quarter of carbon dioxide emitted by humans in the air is absorbed by the ocean. This alters the chemical composition of the sea: a more acidic water threatens the life conditions of organisms whose skeletons or cells are made of calcium carbonate, such as phytoplankton, snails, mussels or, more evident to the human eye, corals. In order to explain children how Ocean Acidification works, we used red cabbage juice, a safe acid/base indicator which reacts in a clear manner to the introduction of CO2 by changing colour.
The star of the show was some red cabbage juice. We poured a very small volume of the cooled juice into test tubes and we asked children to blow through a drinking straw repeatedly for a few minutes until they could see the cabbage juice turn noticeably pinker that the juice in the bottle.
What has happened? The carbon dioxide in the breath combined with the water in the cabbage juice (cabbage is an acid indicator) to form carbonic acid, causing the pH of the solution to drop and the cabbage juice to turn pink.
Why this is interesting? About a quarter of the carbon dioxide released by activities like burning fossils fuels is absorbed by oceans and as a result the ocean water becomes more acidic, like the cabbage juice in the experiment.
Our simple experiment was particularly successful; the children and some of their teachers too, had a lot of fun blowing into the cabbage juice and after the experiment they told us that they now have a better understanding of what ocean acidification is and why it is important.
It was great a experience for us all, as well. The experiment stimulated the imagination of the young students and during the lively discussion afterwards they were able to offer us some out of box thinking and we came up with some rather pioneering ideas and innovative solutions of how to combat ocean acidification.
ParticipantsEleni Angnostou Graeme MacGilhrist Migue Martínez-Botí Athena Drakou
21 May 2013, by Harriet Jarlett – Planet Earth Online
Ocean acidification is damaging some marine species while others thrive, say scientists.
The study, published in PLoS One found that different species react in different ways to changes in their environment. As carbon dioxide emissions dissolve in seawater they lower the pH of the oceans making them more acidic and more corrosive to shells.
Foraminifera and coccoliths, which are small shelled plankton and algae, appear to be surviving remarkably well in the more acidic conditions. But numbers of pteropods and bivalves – such as mussels, clams and oysters – are falling.
‘Ecologically, some species are soaring, whilst others are crashing out of the system,’ says Professor Jason Hall-Spencer, of Plymouth University, who co-authored the paper.
The scientists are unsure whether this drop in certain species is because of changing pH levels, or whether it is due to a combination of stress factors like warming, overfishing and eutrophication -which results from a build up of excess nutrients in water.
‘We found no statistical connection between the abundance of calcifying plankton and the changes in pH. If pH is affecting calcifying plankton in the area then its effect is being masked by other climatic effects. What we do know is that laboratory experiments have shown pH changes affect pteropods adversely,’ he says.
‘The aragonite skeleton of pteropods dissolves more easily in corrosive waters than the low-magnesium calcite that typifies many clams and other molluscs,’ explains Hall-Spencer. ‘But now we think that it’s not as simple as that. It depends partly on how stressed organisms are by other factors, such as lack of food. It also depends on their shape and their ability to protect their skeletons.’
It is possible that the rising levels of CO2 are boosting coccolith numbers by causing them to photosynthesise more and produce more energy.
The scientists used a database collected by the Sir Alaistair Hardy Foundation for Ocean Science, which has been continuously recording levels of plankton in the North Sea since 1931. But, despite being the best database available, it fails to monitor chemical changes, like acid levels, alongside ecological ones, like shifts in pteropod numbers.
Plankton sits at the bottom of the food chains, where it underpins all of our marine food sources. So if numbers drop significantly it could lead to food shortages, particularly in countries where people eat lots of seafood and fish.
The global CO2-carbonic acid-carbonate system of seawater, although certainly a well-researched topic of interest in the past, has risen to the fore in recent years because of the environmental issue of ocean acidification (often simply termed OA). Despite much previous research, there remain pressing questions about how this most important chemical system of seawater operated at the various time scales of the deep time of the Phanerozoic Eon (the past 545 Ma of Earth’s history), interglacial-glacial time, and the Anthropocene (the time of strong human influence on the behaviour of the system) into the future of the planet. One difficulty in any analysis is that the behaviour of the marine carbon system is not only controlled by internal processes in the ocean, but it is intimately linked to the domains of the atmosphere, continental landscape, and marine carbonate sediments.
For the deep-time behaviour of the system, there exists a strong coupling between the states of various material reservoirs resulting in an homeostatic and self-regulating system. As a working hypothesis, the coupling produces two dominant chemostatic modes: (Mode I), a state of elevated atmospheric CO2, warm climate, and depressed seawater Mg∕Ca and SO4∕Ca mol ratios, pH (extended geologic periods of ocean acidification), and carbonate saturation states, and elevated Sr concentrations, with calcite and dolomite as dominant minerals found in marine carbonate sediments (Hothouses, the calcite-dolomite seas), and (Mode II), a state of depressed atmospheric CO2, cool climate, and elevated seawater Mg∕Ca and SO4/Ca ratios, pH, and carbonate saturation states, and low Sr concentrations, with aragonite and high magnesian calcites as dominant minerals found in marine carbonate sediments (Icehouses, the aragonite seas).
Investigation of the impacts of deglaciation and anthropogenic inputs on the CO2–H2O–CaCO3 system in global coastal ocean waters from the Last Glacial Maximum (LGM: the last great continental glaciation of the Pleistocene Epoch, 18,000 year BP) to the year 2100 shows that with rising sea level, atmospheric CO2, and temperature, the carbonate system of coastal ocean water changed and will continue to change significantly. We find that 6,000 Gt of C were emitted as CO2 to the atmosphere from the growing coastal ocean from the Last Glacial Maximum to late preindustrial time because of net heterotrophy (state of gross respiration exceeding gross photosynthesis) and net calcification processes. Shallow-water carbonate accumulation alone from the Last Glacial Maximum to late preindustrial time could account for ~24 ppmv of the ~100 ppmv rise in atmospheric CO2, lending some support to the ‘‘coral reef hypothesis’’. In addition, the global coastal ocean is now, or soon will be, a sink of atmospheric CO2, rather than a source. The pHT (pH values on the total proton scale) of global coastal seawater has decreased from ~8.35 to ~8.18 and the CO32- ion concentration declined by ~19% from the Last Glacial Maximum to late preindustrial time. In comparison, the decrease in coastal water pHT from the year 1900 to 2000 was ~8.18 to ~8.08 and is projected to decrease further from about ~8.08 to ~7.85 between 2000 and 2100. During these 200 years, the CO32- ion concentration will fall by ~ 45%. This decadal rate of decline of the CO32- ion concentration in the Anthropocene is 214 times the average rate of decline for the entire Holocene!
In terms of the modern problem of ocean acidification and its effects, the “other CO2 problem”, we emphasise that most experimental work on a variety of calcifying organisms has shown that under increased atmospheric CO2 levels (which attempt to mimic those of the future), and hence decreased seawater CO32- ion concentration and carbonate saturation state, most calcifying organisms will not calcify as rapidly as they do under present-day CO2 levels. In addition, we conclude that dissolution of the highly reactive carbonate phases, particularly the biogenic and cementing magnesian calcite phases, on reefs will not be sufficient to alter significantly future changes in seawater pH and lead to a buffering of the CO2-carbonic acid system in waters bathing reefs and other carbonate ecosystems on timescales of decades to centuries. Because of decreased calcification rates and increased dissolution rates in a future higher CO2, warmer world with seas of lower pH and carbonate saturation state, the rate of accretion of carbonate structures is likely to slow and dissolution may even exceed calcification. The potential of increasing nutrient and organic carbon inputs from land, occurrences of mass bleaching events, and increasing intensity (and perhaps frequency of hurricanes and cyclones as a result of sea surface warming) will only complicate matters more. This composite of stresses will have severe consequences for the ecosystem services that reefs perform, including acting as a fishery, a barrier to storm surges, a source of carbonate sediment to maintain beaches, and an environment of aesthetic appeal to tourist and local populations. It seems obvious that increasing rates of dissolution and bioerosion owing to ocean acidification will result in a progressively increasing calcium carbonate (CaCO3) deficit in the CaCO3 budget for many coral reef environments. The major questions that require answers are: will this deficit occur and when and to what extent will the destructive processes exceed the constructive processes?
2 Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92093-0202, USA Full text PDF (20MB) | HTML and PDF soon on GeoScienceWorld doi: 10.7185/geochempersp.2.1 | Volume 2, Number 1 (pages 1-227)
A new study, published in PLOS ONE thie month investigates how a strain of the coccolithophore Emiliania huxleyi might respond if all fossil fuels are burned by the year 2100 – predicted to drive up atmospheric CO2 levels to over four times the present day. Specimens grown under this high CO2 scenario were compared with specimens grown under present day CO2 levels.
Below, the press release published at the NOCS website.
Press Release: Marine algae show resilience to carbon dioxide emissions
A type of marine algae could become bigger as increasing carbon dioxide emissions are absorbed by the oceans, according to research led by scientists based at the National Oceanography Centre, Southampton (NOCS).
Coccolithophores are microscopic algae that form the base of marine food chains. They secrete calcite shells which eventually sink to the seafloor and form sediments, drawing down and locking away carbon in rocks. Because of their calcitic shells, some species have been shown to be sensitive to ocean acidification, which occurs when increasing amounts of atmospheric CO2 are absorbed by the ocean, increasing seawater acidity.
But these findings suggest that not all coccolithophore species respond to ocean acidification in the same way.
“Contrary to many studies, we see that this species of coccolithophore gets bigger and possesses more calcite under worst-case scenario CO2 levels for the year 2100,” says Dr Bethan Jones, lead author and former researcher at University of Southampton Ocean and Earth Science, which is based at NOCS. “They do not simply dissolve away under high CO2 and elevated acidity.”
However, the researchers also observed that cells grew more slowly under the high CO2 scenario, which could be a sign of stress.
The researchers also tested for changes in protein abundance – using a technique developed by the collaborating institutes – as well as other biochemical characteristics. They detected very few differences between the two scenarios, indicating that apart from growth, this strain of coccolithophore does not seem to be particularly affected by ocean acidification.
Co-author Professor Iglesias-Rodriguez, formerly at University of Southampton Ocean and Earth Science, says: “This study suggests that this strain of Emiliania huxleyi possesses some resilience to tolerate future CO2 scenarios, although the observed decline in growth rate may be an overriding factor affecting the success of this ecotype in future oceans. This is because if other species are able to grow faster under high CO2, they may ‘outgrow’ this type of coccolithophore.
“Given that chalk production by calcifiers is the largest carbon reservoir on Earth – locking away atmospheric CO2 in ocean sediments – understanding how coccolithophores respond to climate change is a first step in developing models to predict their fate under climate pressure such as ocean acidification.”
The team used a technique called ‘shotgun proteomics’, optimised for marine microbiological research at the University of Southampton’s Centre for Proteomic Research, to detect changes in proteins under the different CO2 scenarios.
The collaborative study involved researchers at University of Southampton Ocean and Earth Science (which is based at NOCS), University of Southampton Institute for Life Sciences, University of Southampton Centre for Proteomic Research, University of Cambridge, University College London and Xi’an Jiaotong-Liverpool University, China.
Microscopic ocean algae called coccolithophores are providing clues about the impact of climate change both now and many millions of years ago. The study found that their response to environmental change varies between species, in terms of how quickly they grow.
Coccolithophores, a type of plankton, are not only widespread in the modern ocean but they are also prolific in the fossil record because their tiny calcium carbonate shells are preserved on the seafloor after death – the vast chalk cliffs of Dover, for example, are almost entirely made of fossilised coccolithophores.
The fate of coccolithophores under changing environmental conditions is of interest because of their important role in the marine ecosystem and carbon cycle. Because of their calcite shells, these organisms are potentially sensitive to ocean acidification, which occurs when rising atmospheric carbon dioxide (CO2) is absorbed by the ocean, increasing its acidity.
There are many different species of coccolithophore and in an article, published in Nature Geoscience this week, the scientists report that they responded in different ways to a rapid climate warming event that occurred 56 million years ago, the Palaeocene-Eocene Thermal Maximum (PETM).
The study, involving researchers from the University of Southampton, the National Oceanography Centre and University College London, found that the species Toweius pertusus continued to reproduce relatively quickly despite rapidly changing environmental conditions. This would have provided a competitive advantage and is perhaps why closely-related modern-day species considered to be its descendants, (such as Emiliana huxleyi) still thrive today.
In contrast, the species Coccolithus pelagicus grew more slowly during the period of greatest warmth and this inability to maintain high growth rates may explain why its descendants are less abundant and less widespread in the modern ocean.
“This work provides us with a whole new way of looking at living and fossil coccolithophores,” said lead author Dr Samantha Gibbs, Senior Research Fellow at University of Southampton Ocean and Earth Science.
By comparing immaculately preserved and complete fossil cells with modern coccolithophore cells, the researchers could interpret how different species responded to the sudden increase in environmental change at the PETM, when atmospheric CO2 levels increased rapidly and the oceans became more acidic.
“We use knowledge of how coccolithophores build their calcite skeletons in the modern ocean to interpret how climate change 56 million years ago affected the growth of these microscopic plankton,” said co-author Dr Alex Poulton, a Research Fellow at the National Oceanography Centre.
“This is a significant step forward and allows us to view fossils as cells rather than dead ‘rocks’. Through this we can begin to understand the environmental controls on oceanic calcification, as well as the potential effects of climate change and ocean acidification.”
Reference: Gibbs S.J., Poulton A.J., Bown P.R., Daniels C.J., Hopkins J. Young J.R., Jones H.L., Thiemann G.J., O’Dea S.A., Newsam C. (2013) Species-specific growth response of coccolithophores to Palaeocene–Eocene environmental change. Nature Geoscience doi: 10.1038/NGEO1719
The study was primarily supported by the UK Ocean Acidification Research Programme, which is jointly funded by the Natural Environment Research Council (NERC), the Department of Environment, Food and Rural Affairs (Defra) and the Department of Energy and Climate Change (DECC).
It seems that Paul’s Bown and Samantha’s Gibbs talk at the Third Symposium on The Ocean in a High-CO2 World, held on 24-27 September in Monterey, stimulated a lot of discussion among science journalists. Science magazine run a piece on their news page.
Here an extract from the article.
The meeting was a coming-out party of sorts for scientists interested in the biological implications of the chemical changes occurring as the oceans absorb huge and growing amounts of atmospheric carbon dioxide. Just 8 years ago, an inaugural symposium on the topic in Paris drew only 125 researchers from 20 nations; this year, more than 550 scientists from 40 nations showed up. The field is getting “much bigger and more competitive,” Gattuso says.
Acidification researchers are also shifting their focus. To date, many experiments have involved simply plopping sea creatures into laboratory tanks full of acidified water for a few days or months to see how they respond. Many species suffer, researchers reported. Fish and shellfish larvae exposed to more acidic waters, for example, often fail to thrive: They don’t grow as big or live as long as those born in more alkaline waters. But some species show substantial resilience, reported biologist Sam Dupont of the University of Gothenburg, Kristineberg, in Sweden. After he used acidic water to completely dissolve the shells of developing sea urchins, for instance, the urchins were able to regrow them and live normally once they were returned to normal seawater.
Such limited studies, however, “can’t really tell you whether a species has the capacity to adapt to acidification, or how pH changes affect a larger ecosystem,” says marine scientist Gretchen Hofmann of the University of California, Santa Barbara.
One approach to leaping those limitations is to go back to the future, by looking for times in the fossil record when ocean ecosystems experienced similarly dramatic carbon dioxide–driven changes. One popular candidate, known as the Paleocene-Eocene Thermal Maximum (PETM), occurred 55 million years ago during rapid global warming (Science, 18 June 2010, p. 1500). Increasingly corrosive bottom waters appear to have helped drive many bottom-dwelling species extinct during the PETM, reported paleontologist Paul Bown of University College London. But what happened at the ocean’s surface is less clear. The fossil record suggests that many species of phytoplankton—the tiny plants at the base of the marine food chain—also disappeared but were replaced by other species, with little change in overall diversity.
But such coarse measures can’t tell you how ancient acidification might have affected reproduction or growth patterns in these marine communities, Bown says. To get that more detailed view, Bown and his colleagues have been analyzing some exquisitely preserved fossils of PETM phytoplankton called coccolithophores, which surround themselves with shieldlike plates of shell. By studying some closely related living species, the researchers found that they could estimate ancient coccolith growth and reproduction patterns by painstakingly counting the plates on individual fossils. (The number increases as the organisms grow.) So far, preliminary studies haven’t found deformed shells or other dramatic signs of lower pH, but Bown cautions against taking that as a sign that modern acidification won’t be a problem. Change in the PETM moved “much, much slower than today,” he says.
Read the full article: Science 5 October 2012: Vol. 338 no. 6103 pp. 27-28, DOI: 10.1126/science.338.6103.27
The Ocean Acidification talk that Paul Bown and Samantha Gibbs presented in the Third Symposium on The Ocean in a High-CO2 World, held on 24-27 September in Monterey, provoked interest from the journalists, and Nature have run a short piece on their News page .
The burning of fossil fuels is releasing vast quantities of extra carbon dioxide (CO2) to the Earth’s atmosphere. While a proportion of this stays in the atmosphere, raising atmospheric CO2 levels, around half is removed over time, either to become sequestered in trees and plants or to become absorbed in the ocean. When it dissolves in the ocean, CO2 changes the chemistry of the water, making it more acidic. As a result the oceans are around 30% more acidic today than they were before the industrial revolution – a process known as ocean acidification. In this weeks issue of Science a paper by a team of scientists from various research institutions worldwide, including Dr Samantha Gibbs and Dr Gavin Foster from the Ocean and Earth Science, National Oceanography Centre, University of Southampton, puts this unprecedented change in its geological context.
The geological record contains evidence for a variety of long-term global environmental perturbations along with their associated biotic responses, including several well studied natural ocean acidification events. By studying such events in the past we may be able to see how the Earth System has reacted to ocean acidification before and so how it may respond in years to come. In this new study, the result of a workshop led by Columbia University’s Lamont-Doherty Earth Observatory and the University of Bristol, the most commonly cited examples of the last 300 million years are critically examined, including the asteroid impact that made the dinosaurs go extinct and the Permian mass-extinction which wiped out around 95 per cent of all life on Earth. Then, these events were ranked according to their similarity with the modern situation, in terms of the magnitude and rate of carbon emissions.
Dr. Samantha Gibbs, an expert on microscopic plankton fossils, says “all these events provide valuable insights but the massive global warming event 56 million years ago known as the Palaeocene-Eocene thermal maximum clearly stands out. Although not even this event is large enough to parallel the unprecedented CO2 rise that is currently underway”. Dr. Gavin Foster added “However, by studying it, and similar events in some detail, we may still be able to learn something very useful about what levels and rates of acidification have proven particularly dangerous to the Earth System in past”.
Dr Gibbs and Dr Foster are funded by the Royal Society and NERC, as part of a number of UK-wide research initiatives (http://www.oceanacidification.org.uk/ and www.descentintotheicehouse.org.uk), reconstruct the environment of the past and examine the biotic response to wide range of natural climate change events.
For more information on ocean acidification research activities and opportunities at OES and NOCS please contact Athena Drakou A.Drakou@soton.ac.uk
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