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.

Limacina helicina. Credit: Planet Earth

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.

Without improved monitoring , researchers say they will struggle to accurately test the consequences of ocean acidification.

‘CO₂ is driving down the pH of water, but finding evidence for that and its ecological effects is proving tricky. Most work is done in the lab, so there’s not much good long term data on changes in the water,’ says Hall-Spencer.

Coccoliths appear to be able to cope with recent changes to their environment, the scientists don’t know how they will fare in the future.

‘We need an observing network to keep track of the effects of ocean acidification both chemically and biologically. Ecosystems are going to change, and if we want to protect fisheries, food sources and jobs we need to be forewarned,’ he concludes.

Read more: Beare D, McQuatters-Gollop A, van der Hammen T, Machiels M, Teoh SJ, et al. (2013) Long-Term Trends in Calcifying Plankton and pH in the North Sea. PLoS ONE 8(5): e61175. doi:10.1371/journal.pone.0061175

In the website you can also read an interesting article by Robert Monroe, (an abstract, below) about “What Does 400 ppm Look Like?” as scientists are looking back to Pliocene as a guide for things to come.

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The Pliocene is the geologic era between five million and three million years ago. Scientists have come to regard it as the most recent period in history when the atmosphere’s heat-trapping ability was as it is now and thus as our guide for things to come.

Foram art: calcite tests of selected benthic (left) and planktonic (right) foraminifera. These are from exceptionally well-preserved Paleogene sediments of Tanzania (33–45 Ma). Scale is approximate; diameters are from about 0.20–0.75 mm. Images: P. N. Pearson and I. K. McMillan. Courtesy: Paul Peason Source: OXYGEN ISOTOPES IN FORAMINIFERA: OVERVIEW AND HISTORICAL REVIEW

Recent estimates suggest CO₂ levels reached as much as 415 parts per million (ppm) during the Pliocene. With that came global average temperatures that eventually reached 3 or 4 degrees C (5.4-7.2 degrees F) higher than today’s and as much as 10 degrees C (18 degrees F) warmer at the poles. Sea level ranged between five and 40 meters (16 to 131 feet) higher than today.

As for what life was like then, scientists rely on fossil records to recreate where plants and animals lived and in what quantity. Pliocene fossil records show that the climate was generally warmer and wetter than today.  Maps of Pliocene vegetation record forests growing on Ellesmere Island in the Canadian Arctic, and savannas and woodlands spreading over what is now North African desert. Both the Greenland and Antarctic ice sheets were smaller than today during the warmest parts of the Pliocene.

In the oceans, fossils mark the spread of tropical and subtropical marine life northward along the U.S. Eastern Seaboard.  Both observations and models of the Pliocene Pacific Ocean show the existence of frequent, intense El Niño cycles—a climatic oscillation that today delivers heavy rainfall to the western U.S. causing both intense flooding but also increasing the river flows needed to sustain salmon runs. The absence of significant ocean upwelling in the warmest part of the Pliocene would have suppressed fisheries along the west coasts of the Americas, and deprived seabirds and marine mammals of food supplies.  Reef corals suffered a major extinction during the peak of Pliocene warmth but reefs themselves did not disappear.

Richard Norris, a geologist at Scripps Institution of Oceanography, UC San Diego, said the concentration of CO₂ is one means of comparison, but what is not comparable, and more significant, is the speed at which 400 ppm is being surpassed today.

“I think it is likely that all these ecosystem changes could recur, even though the time scales for the Pliocene warmth are different than the present,” Norris said.  “The main lagging indicator is likely to be sea level just because it takes a long time to heat the ocean and a long time to melt ice. But our dumping of heat and CO₂ into the ocean is like making investments in a pollution ‘bank,’ since we can put heat and CO₂ in the ocean, but we will only extract the results (more sea-level rise from thermal expansion and more acidification) over the next several thousand years.  And we cannot easily withdraw either the heat or the CO₂ from the ocean if we actually get our act together and try to limit our industrial pollution–the ocean keeps what we put in it.”

Read more……..

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 CO₃^2- 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 CO₃^2- ion concentration will fall by ~ 45%. This decadal rate of decline of the CO₃^2- 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 CO₃^2- 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?

Read more….

The Marine Carbon System and Ocean Acidification during Phanerozoic Time
Fred T. Mackenzie¹ and Andreas J. Andersson²

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).

Example of coccoliths derived at the end of the experiment

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.

Discovering the world under the microscope

Another very successful Ocean and Earth Open Day held at NOC, Southampton on Saturday 23 March, 2013. A great turnout on a very cold day, we had over 3000 visitors and the feedback was extremely positive.

The Descent into the Icehouse  (@IntotheIcehouse) participated in the event with a poster display and information material about our research work.  We had a great attendance; our stand was full most of the time and it was a rewarding and exciting experience for both us and the visitors. It was fantastic to see the excitement in the children’s faces discovering through a microscope the tiny world of microfossils and especially those of foraminifera, a group of single-celled animals that construct shells of almost infinite variety and in most geographical regions.

The study of fossil foraminifera has many applications beyond expanding our knowledge of the evolution and diversity of life. Fossil foraminifera are useful in paleoecology, paleobiogeography, as well as, oil exploration.

The children and their parents had a great time exploring and discovering the wonders of nature and a whole world under the microscope.

Our OED day would not happen without the help of our scientists and volunteers

… and without their enthusiasm, dedication, determination and sheer hard work, this day could not be such a success.  I’d like to take this opportunity to say again a very big THANK YOU.

More photos and a video will be made available from NOC online soon, so look out for another post in the next few weeks.

In his Skeptical Science blogpost, Rob Painting discusses the key points of the study which has engaged scientists in a constructive debate in the comments section.

Key Points:

• Because the water contained in land-based ice sheets is ultimately derived from the ocean, over long (geological) timescales global sea level is largely determined by global temperature and, consequently, the temperature-dependent volume of ice stored on land.

• Since the concentration of carbon dioxide in the atmosphere (The Greenhouse Effect) exerts such a powerful influence on global and polar temperature, it therefore follows that it should also exhibit a strong relationship with global sea level over geologic intervals of time.

• Foster & Rohling (2013) examined time slices of paleo data covering the last 40 million years to uncover the details of this carbon dioxide-sea level relationship. Surprisingly, they found a consistent and robust relationship between carbon dioxide and sea level irrespective of other contributing factors.

• Based on the concentration of carbon dioxide in the atmosphere as of 2011, the authors estimated that future sea level is committed to rise 24 metres (+7/-15 m) above present-day once the land-based ice sheets have fully responded to the warming and the Earth is once more in equilibrium.

• The authors estimated that this sea level rise will likely take place over many centuries, if not several thousand years, but it nevertheless represents the long-term consequences of human industrial activity, and is further evidence that CO₂ is the Earth’s “main control knob” for global temperature.

Continue reading here

We had a lively discussion and several issues have been raised, some of the most interesting ones were:

1.  The timescales of global climate change are very different between early Cenozoic and future predictions; how does understanding the Cenozoic help us predict the future?
2. Ice caps seem to show a nonlinear response to climate forcing during melting due to a hysteresis effect, but will this hold true on current time scales? Could this response eventually manifest itself into hastened melting as opposed to persistence of ice caps?
3. On early Cenozoic time scales, how much does the distance of the Earth’s orbit from the sun implicate atmospheric CO2 levels and how much of that theory is guesswork?

 The most intriguing point to me was the question if the change in sea surface temperature was due to decline carbon dioxide concentrations, why/how did the tropics remain fairly stable during the Eocene? What are the possible mechanisms such as different ocean circulation, different atmospheric circulation, or something having to do with the uneven radiation from the sun based on latitude?

 Well…. the answer to this question will have to wait until we have generated more data…

Overall, it was a great experience that I would certainly do again.

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