Google Analytics Alternative

You are browsing the archive for Ocean acidification.

Fish on acid lose fear of predators

April 15, 2014 in Adaptation, Carbon Dioxide, Marine ecology, Ocean acidification

FOR IMMEDIATE RELEASE

Reef species like this clown fish are at higher risk of succumbing to predators in more acid seas Image: Ritiks via Wikimedia Commons

Reef species like this clown fish are at higher risk of succumbing to predators in more acid seas
Image: Ritiks via Wikimedia Commons

By Tim Radford

As carbon dioxide makes the seas more acidic and poses physical problems for some species of fish, it can also rob them of their inhibitions, which helps their predators.

LONDON, 15 April – Coral reef fishes exposed to acid oceans lose their sense of smell – and their sense of caution – and are more likely to fall prey to natural enemies, according to new research in Nature Climate Change.

The finding is based on observations of the behaviour of four species at a reef off the coasts of Papua New Guinea where natural carbon dioxide seeps out of the rock, and confirms a series of other such studies in the last year.

A cool volcanic discharge in the reef has served as a natural laboratory for years: water in the region reaches an average pH of 7.8. This standard measure of acidity is co-incidentally the level predicted for all the world’s oceans by 2100, as atmospheric carbon dioxide levels continue to rise, according to the Intergovernmental Panel on Climate Change. www.ipcc.ch/

Australian and US scientists observed the fishy behaviour from a boat moored above the reef, and also tested the fish on board the vessel. What they observed was that, away from the volcanic bubbles of carbon dioxide, in conditions of more normal ocean chemistry, damsel fish and cardinal fish seemed able to smell predators and stayed in sheltered places in the reef to avoid becoming prey.

Fish from the waters richer in carbonic acid seemed not to sense the presence of predators, and were more likely to venture into dangerous waters.

Survival threat

After a sudden scare that sent all the fish racing for cover, the fish from the bubble reef ventured forth much sooner. In normal circumstances, such fish spend 80% of their time under cover.

The bubble reef fish spent at most only 12% of their time in hiding. Mortality accordingly was five times higher.
“Their sense of smell was acutely affected in CO2-rich waters in ways that gravely threaten their survival,” said Alistair Cheal of the Australian Institute of Marine Science.

“We were able to test long-term realistic effects in this environment,” said another author, Danielle Dixson of the Georgia Institute of Technology in the US. “One problem with ocean acidification research is that it’s all laboratory-based, or you’re testing something that’s going to happen in 100 years’ time with fish that are from the present day, which is not actually accurate.”

The reasoning is that the change in pH levels disrupts a neuroreceptor in the fishes’ brains and affects faculties or alters behaviour. Similar experiments with Californian rockfish have demonstrated much the same effect.

Acid spreading

But increased acidification of the oceans is also likely to affect shellfish and corals in other ways, and research in the Great Barrier Reef region of Australia has documented a dramatic behaviour change in a jumping snail that suggested impaired decision-making capability as pH levels alter.

Sea water is already 30% more acidic that it was at the start of the Industrial Revolution 200 years ago. The rate of change is at least 100 times faster than at any time in the last 650,000 years.

The bubbling waters of the reef under test are not unique – such localized carbonic acid seeps occur in many places all over the world – and the fact that predators might find easy pickings in such places makes no real difference to population levels in the vastness of the rest of the ocean. But such experiments raise the question: can ecosystems adapt to changing water chemistry?

“Continuous exposure does not reduce the effect of high CO2 on behaviour in natural reef habitat and this could be a serious problem for fish communities in the future when ocean acidification becomes widespread as a result of continued uptake of anthropogenic CO2 emissions,” the authors conclude. - Climate News Network

Climate science ‘is beyond argument’

March 17, 2014 in Arctic, Business, Carbon, Climate deniers, Deep Ocean, Economy, Fish, Food security, Global Ocean Commission, Ice Loss, Marine ecology, Ocean acidification, Ocean Warming, Polar ice, Pollution, Science

FOR IMMEDIATE RELEASE

Not as sunny as it seems: The ocean is under attack on many fronts, with climate change foremost among them Image: kein via Wikimedia Commons

Not as sunny as it seems: The ocean is under attack on many fronts, with climate change foremost among them
Image: kein via Wikimedia Commons

By Alex Kirby

The Global Ocean Commission says climate change is one of the key threats to the health of the world’s marine life, which it says faces multiple pressures in a warming world.

HONG KONG, 17 March - South Africa’s former Finance Minister, Trevor Manuel, has derided those who deny the scientific argument that climate change is an urgent problem caused largely by human activity.

He told journalists here: “The science is now incontrovertible. There are a few people in the world who deny it, but they are mainly in lunatic asylums.”

Mr Manuel is one of three co-chairs of the Global Ocean Commission, a panel of global leaders who have just ended a meeting here to finalise the proposals they will present to the United Nations in June.

The meeting agreed that another key threat to the world’s oceans is overfishing and the subsidies which help to make it possible. It says this, and the other factors causing ocean degradation, threaten the food security of as many as 500 million people.

It is deeply worried about pollution. With plastic remains now so pervasive that they are found even in deep seafloor sediments, Mr Manuel said, it sometimes seemed that “you might as well not bother to buy seafood at all – just buy the plastic bag it comes in and eat that.”

Shells corroded

The Commission says climate change threatens the oceans in three main ways: by raising the temperature of the water; by reducing its oxygen content; and by increasing its acidity. Antarctic pteropods, small sea snails also known as sea butterflies, are already being found with severely corroded shells because of acidification, and larger creatures, including bigger shellfish and corals, are likely to be seriously affected.

Another of the co-chairs, José María Figueres, the former president of Costa Rica, told the Climate News Network the Commission was concerned at the prospect of exploitation of the high seas in the Arctic as the region’s sea ice continues to melt.

He said: “Beyond Arctic countries’ EEZs (exclusive economic zones stretching 200 nautical miles from the coast), the melting will leave us with a doughnut-shaped hole in the Arctic high seas, which are not under international control.

“Some nations are now looking to explore there for fish, minerals, valuable biodiversity and other resources. I believe we should not go down that route.

We should listen to the science and follow the precautionary principle, keeping this pristine area off-limits for exploitation until we understand the consequences.

Coalition builders

“We’re already pushing the high seas to the limit. We don’t need to push them over the edge by a lack of proper precaution in the Arctic.”

He said: “The jury is still out on whether we have 20 or 30 years ahead as a window of opportunity to act. But why wait? Listen to the science, which is overwhelming, and to the economics, which are sound.”

Describing the Commission as “not just a bunch of treehuggers, but a group that’s grounded itself in good sound economics”, Mr Figueres said the recommendations it planned to present to the UN on 24 June would represent about 20% of its work. The other 80% would involve building coalitions around each recommendation: there are expected to be no more than 10 in total.

The Commission’s third co-chair is the UK’s former Foreign Secretary, David Miliband. He told the Network: “Answers that sit on a shelf are a waste of time, and people who are positively inclined to protect the oceans are held back by institutional inertia.

“But the interplay between climate change and ocean damage is rising, and it very much needs to. The science of most of the last half-century shows us how we’ve been playing tricks with nature.” – Climate News Network

Climate technofixes ‘will not work’

March 7, 2014 in Adaptation, Deserts, Geoengineering, Marine ecology, Ocean acidification, Technology

FOR IMMEDIATE RELEASE

Plant forests in the desert? That would  alter ocean circulation Image: Jamou via Wikimedia Commons

Plant forests in the desert? That would alter ocean circulation
Image: Jamou via Wikimedia Commons

By Tim Radford

Hopes that we may be able to use geo-engineering to avert dangerous levels of climate change have been dashed by a German research team.

LONDON, 7 March – Global warming will be bad. Geoengineering could make it worse. Once again, a research team has considered all the benefits of climate technofix  – that is, deliberate steps to neutralize the consequences of unrestrained greenhouse gas emissions – and come to a grim conclusion.

At the best, any attempt to geo-engineer the changing climate back to its starting point would be relatively ineffective. At the worst, it would have “severe climatic side effects.”

David Keller and colleagues from the Helmholtz Centre for Ocean Research in Kiel, Germany and colleagues report in Nature Communications that they used an earth system model to simulate five very different strategies to reduce the rate of global warming and keep the climate from dramatic change.

Geo-engineering is a catch-all phrase for some very different approaches. One favoured and much-examined technique is to counter global warming by reducing the levels of sunlight that hit the planet’s surface, a technique called solar radiation management.

This approach has already been comprehensively dismissed by other studies, which have demonstrated that such an approach could change rainfall patterns or make conditions worse in arid zones such as the Sahel or just make things worse once the technology ceased.

But the Helmholtz team decided to look at the bigger picture: although climate scientists have repeatedly warned that the only safe answer is to reduce – and go on reducing – fossil fuel emissions, and although governments have acknowledged the urgency of the problem, very few really effective steps have been taken.

Varied options

So the technofix remains an option. How effective could it be? What could climate engineers do? There are plenty of powerful ideas. One of these is to exploit the appetite of green things for carbon dioxide: for instance, to irrigate the Australian and Sahara deserts and grow forests that will soak up more carbon.

Another is to nourish the ocean surface waters, by pumping deep, nutrient-rich bottom water to the surface to give algae a chance to bloom across the oceans. A third is to add lime to the oceans and chemically increase the uptake of carbon dioxide.

And then – still at sea – ships could spread that vital trace element iron across the ocean surfaces and give plankton a chance to bloom, grow, die and take all that carbon down to the seabed out of harm’s way.

And lastly, there is solar radiation management, either by pumping sulphate aerosols into the stratosphere, or putting reflectors in space: anything that reduces the sunlight levels a little could balance the impact of the greenhouse gas build-up.

The researchers simply contemplated the crude consequences of each step. They did not concern themselves with the economic, political and technological feasibility of each, nor the ethical questions. They just wanted to know whether any or all of these options could possibly work.

Limited potential

The answer, spelled out in 11 pages of close argument, is, basically, no. Could any of these limit warming? By about 8% perhaps: not nearly enough. Could all of them together have an effect? Even a combination of approaches could not stop global warming increasing by a lot more than 2°C by 2100 under the notorious “business as usual” scenario.

Would they have side effects? Yes, afforestation of deserts (if it could be done) would increase the local temperatures and increase freshwater flow and thus reduce the salinity of the oceans and change circulation patterns.

Ocean upwelling would increase the regions of the ocean with low oxygen – bad for living things – and precipitate rapid climate change if the upwelling stopped. Iron fertilization would increase ocean acidification and solar radiation management would do exactly what previous researchers have already said: change the weather patterns with alarming consequences and make things worse when the programme halts.

The message is: the most effective way to prevent further climate change is to limit carbon dioxide emissions.

“We find that even when applied continuously at scales as large as currently deemed possible, all methods are, individually, either relatively ineffective with limited warming reductions, or they have potentially severe side effects and cannot be stopped without causing rapid climate change,” the authors write.

“Our simulations suggest that the potential for these types of climate engineering to make up for failed mitigation may be very limited.” – Climate News Network

Shellfish feel impact of more acid seas

January 22, 2014 in Adaptation, Algae, Carbon Dioxide, Fish, Greenhouse Gases, Marine ecology, Ocean acidification, Predation, USA

FOR IMMEDIATE RELEASE

Low oxygen and rising acidity in the oceans spell trouble for some species of scallop Image: By Jeremy Keith from Brighton & Hove, UK

Low oxygen and rising acidity in the oceans spell trouble for some species of scallop
Image: By Jeremy Keith from Brighton & Hove, UK, via Wikimedia Commons

By Tim Radford

Researchers in the US have discovered that several more marine species are being damaged by the effects of the increasing acidity of the oceans, a direct consequence of greenhouse gas emissions.

LONDON, 22 January – Ocean acidification brings fresh problems for Californian native oysters. Like some creature from a horror movie, a driller killer threatens Ostrea lurida, the Olympia oyster that dwells in the estuaries of western North America.

Many species are likely to face problems as pH levels (which measure how acid a liquid is) change and ocean chemistry begins to alter as the world warms and ever more dissolved carbon dioxide flows into the sea and adds to its acidity.

Researchers have observed that coral skeletons are affected and larval oysters find it more difficult to build their first shell structures. The change towards greater acidity seems to trigger learning difficulties in juvenile rockfish  and make it harder for the conch snail to leap out of the way of a predator’s poisoned dart. And three separate research papers bring yet more bad news for yet more sea creatures.

Eric Sanford and colleagues at the University of California, Davis, report in the Proceedings of the Royal Society B that under more acid water conditions, the Olympia oyster experiences a 20% increase in drilling predation.

Researchers conducted a direct experiment involving oysters reared in normal conditions, oysters reared in water high in dissolved carbon dioxide, and an invasive predator from a distant ocean called Urosalpinx cinerea, the Atlantic oyster drill. Their assumption was that bivalves (creatures with a hinged shell) in more acid water would grow thinner shells, and that drilling predators would selectively choose the victims that would be easiest to drill into.

Problems multiply

It didn’t work quite like that – the experimental oysters did not have thinner shells. But these oysters were victims all the same. They were 30% to 40% smaller than the control group of oysters in the other tank “and these smaller individuals were consumed at disproportionately greater rates”, the authors say. The invasive snails, on the other hand, were not bothered by the change in water pH.

The results indicate, say the researchers, that ocean acidification “can negatively affect the early life stages of Olympia oysters.” They have been subjected already to overfishing, disease, habitat loss, pollution and hypoxia, when water is so rich in nutrients that it becomes starved of oxygen and turns into a dead zone where nothing much can survive for long. Extra vulnerability to an invasive driller killer is, the scientists carefully say in non-emotive language, “a relatively novel stressor for this species.”

Hypoxia, too, turns out to be a problem made worse by carbon dioxide. Low oxygen waters are already acidified waters, say Christopher Gobler of Stony Brook University in the US and colleagues in the Public Library of Science journal PLOS One.

They report that a combination of low oxygen and low pH led to higher rates of death and slower growth for young bay scallops and hard clams than expected from either individual factor. “Low oxygen zones in coastal and open ocean ecosystems have expanded in recent decades, a trend that will accelerate with climatic warming”, says Gobler.

Threat to algae

“There is a growing recognition that low oxygen regions of the ocean are also acidified, a condition that will intensify with rising levels of atmospheric CO2 due to the burning of fossil fuels causing ocean acidification. Hence the low oxygen, low pH conditions used in this study will be increasingly common in the world’s oceans in the future.”

And ocean acidification is not just making life good for predators and bad for the prey, it could be threatening to alter the basic biodiversity of the sea. Sophie McCoy of the University of Chicago reports in Ecology Letters that she and Cathy Pfister looked at the dynamics of coralline algae that live around Tatoosh Island, Washington, on the Pacific coast of the US.

These little creatures, like oysters, grow calcium carbonate skeletons. In previous observations in which four species were transplanted to these waters, one species called Pseudolithophyllum muricatum emerged as the undisputed winner. In the 1980s, its skeleton grew twice as thick as its competitors’.

In the latest round of tests, there was no clear winner: no species was dominant, and P. muricatum won less than 25% of the time – a response, the authors think, to changes in the pH of the sea water just in the last 12 years.

The total energy available to the organisms was the same, but their responses were different: those that needed to make more calcium carbonate tissue were under more stress than those that did not.

This experiment was a “real world” test rather than a laboratory experiment. “Field sites like Tatoosh are unique because we have a lot of historical ecological data going back decades,” said McCoy. “I think it is really important to use that in nature to understand what is going on.” – Climate News Network

Acid oceans threaten jumping snail

January 9, 2014 in Adaptation, Marine ecology, Ocean acidification

FOR IMMEDIATE RELEASE

By Tim Radford

Carbon emitted into the atmosphere is helping to make the oceans more acid, and that’s not good news for some of the species that live there.

LONDON, 9 January – A submarine snail with an unexpected talent for the high jump could be one of the great losers in a warmer, carbon dioxide-rich world.

The conch snail Gibberulus gibberulus gibbosus is a gastropod that is notoriously nimble on its single foot. When it scents danger from its biggest predator, the marbled cone shell, it takes what is (for a snail) a great leap backward and slightly sideways out of danger from the attacker’s poisoned dart. In July last year it demonstrated an unexpected ability to stay cool and leap out of harm’s way even when the seawater had warmed to near lethal levels.

But, according to new research published in the Proceedings of the Royal Society B, the great challenge for the spring-loaded conch snail is not likely to be a warmer ocean, but a more acidic one.

A humpback conch snail (L) leaps backwards away from the predatory marbled cone (R) Image: Courtesy of Sue-Ann Watson

A humpback conch snail (L) leaps backwards away from the predatory marbled cone (R)
Image: Courtesy of Sue-Ann Watson

As carbon dioxide levels rise, the seas have become more acidic. Surface sea water’s pH – a measure of acidity – is lower and 30% more acidic than it was 200 years ago, at the start of the Industrial Revolution. The rate of change in this acidity is about 100 times faster than at any period in the last 650,000 years.

This is almost certain to create problems for reef corals, and for molluscs that exploit the water’s chemistry to build their primary defence, the shell. But according to Sue-Ann Watson of Australia’s Centre of Excellence for Coral Reef Studies, this increasing acidity is also likely to play havoc with the conch snail’s nervous system.

She and colleagues tested Gibberulus in laboratory tanks that held water at the pH levels expected in the decades to come and found that the chemistry of the water had a serious effect on snail behaviour.

Delayed response

The number of snails that jumped to escape a predator fell by half, those that did jump were slower to leap out of danger, and when they did, they used a different escape trajectory.

It wasn’t a question of physical ability: what had happened was that the snail’s decision-making capacity had become impaired. In the unforgiving world of predator and prey, a slow-to-respond conch snail is likely to become a soft target; in hunter’s parlance, a sitting duck.

That the nervous systems of the little laboratory snails were impaired became much clearer when researchers treated the test tank water with gabazine, a natural chemical that helps the functioning of the neurotransmitter receptors in the creature’s response machinery. Once this had been applied, Gibberulus started behaving more normally.

This research echoes earlier studies in California and in Sweden of the effects of changed pH levels on the learning behaviour of juvenile rockfish, and the digestive systems of sea urchins. There too, experiments showed that some kind of nervous system interference was at work.

“This neurotransmitter receptor is common in many animals and evolved quite early in the animal kingdom”, said Göran Nilsson of the University of Oslo, one of the authors.

“So what this study suggests is that human carbon emissions directly alter the behaviour of many marine animals, including much of the seafood that is part of human diet.” – Climate News Network

Researchers study shellfish success

December 24, 2013 in Adaptation, Antarctic, Europe, Fish, Marine ecology, Ocean acidification

FOR IMMEDIATE RELEASE

Scottish musel beds: The European research will be globally relevant Image: Copyright and courtesy of SAMS

Scottish mussel beds: The European research will be globally relevant
Image: Copyright and courtesy of SAMS

By Alex Kirby

The British Antarctic Survey is leading a research programme aimed at helping the European fishing industry and monitoring the effects of climate change on several shellfish species.

LONDON, 24 December – If you like the occasional plate of grilled scallops or fancy an oyster now and then, read on and ponder. The health of several species of European shellfish is under threat.

The bad news is that the shellfish face an uncertain future as the oceans become warmer and more acidic because of the changing climate. But there is some better news too: the European Union is funding an international research team to work out how these changes will affect several species vital to the European fishing economy and to marine biodiversity.

Scientists do not fully understand how shellfish like oysters, mussels, scallops and clams produce their shells, or how a change in environment will affect their populations. To address this the EU is funding a €3.6 million (£3 m) programme called CACHE (Calcium in a Changing Environment). Shellfish are an important part of the European marine economy which provides an estimated 5.4 million jobs.

Coordinated from the British Antarctic Survey (BAS) in Cambridge, UK, the programme will research how the animals produce their shells. The scientists will also try to identify populations which are resilient to climate change.

These relatively small animals are important as part of the wider pattern of marine biodiversity. And, as they make their shells from calcium carbonate, they also help to absorb the greenhouse gas CO2 from seawater.

Biotech applications

The risk to them comes from their dependence on calcium carbonate – a substance which dissolves under acidic conditions.  As the oceans become warmer and more acidic their shells will either thin, or the animals will have to expend more energy on producing thicker shells.  This will affect their population sizes and the quality of their flesh, directly affecting fisheries and consumers.

How shellfish produce their shells also matters to the biotech industry, which is interested in imitating (in a process known as bio-mimicry) the way in which shellfish take a soluble compound like calcium to make solid, robust structures.

A better understanding of this could reduce the carbon footprint of producing construction materials and create the potential for “fixing” CO2 into the building process.

The species the research team is looking at are the king scallop, the Pacific oyster, the blue mussel and the soft shell clam. It will also study the native oyster to help conservation plans, as it is listed as a priority species in the UK.

Iceberg protection

Dr Melody Clark of BAS, the programme coordinator, told the Climate News Network: “The programme is driven by the science. We really don’t know the fundamentals of how shellfish respond to changing environments.

“We do know that, in response to environmental conditions, they can change how much shell they produce, for example growing thicker shells in response to predators. In the Antarctic, inter-tidal limpets grow much thicker shells than sub-tidal ones, because they are bashed by icebergs.

“And we don’t know just how they make their shells, whether with calcium from their food, or from the seawater.

“On bio-mimicry, this research may let us start to develop ways of producing more robust structures without carbon, and with little energy.

“We’re researching shellfish in European waters, but we’re recruiting the researchers worldwide, and the results will be relevant beyond Europe.” – Climate News Network

Earth ‘may be doubly sensitive’ to CO2

December 11, 2013 in Arctic, Climate Sensitivity, IPCC, Ocean acidification, Palaeoclimatology

FOR IMMEDIATE RELEASE

Bad news for bears - snd for us: Geological proof as well as models show rising CO2 is melting polar ice Image:Alastair Rae via Wikimedia Commons

Bad news for bears – snd for us: Geological evidence as well as models prove rising CO2 is melting polar ice
Image: Alastair Rae via Wikimedia Commons

By Alex Kirby

The sensitivity of the Earth system to a doubling of atmospheric carbon dioxide may be twice as great as scientists had thought, new climate records from the distant past suggest.

LONDON, 11 December – You may think the prospect of climate change is alarming, a call to action to slow down our emissions of carbon dioxide and other greenhouse gases.

You’re almost certainly right. But some scientists are now suggesting you should be much more concerned than you are, because they think we may be seriously underestimating the problem.

The Geological Society of London (GSL) says the sensitivity of the Earth’s climate to CO2 could be double earlier estimates.

The Society has published an addition to a report by a GSL working party in 2010, which was entitled Climate change: Evidence from the Geological Record.
The addition says many climate models typically look at short term, rapid factors when calculating the Earth’s climate sensitivity, which is defined as the average global temperature increase brought about by a doubling of CO2  in the atmosphere.

Scientists agree that a doubling of atmospheric CO2 levels could result in temperature increases of between 1.5 and 4.5°C, caused by rapid changes such as snow and ice melt, and the behaviour of clouds and water vapour.

But what the GSL now says is that geological evidence from palaeoclimatology (studies of past climate change) suggests that if longer-term factors are taken into account, such as the decay of large ice sheets, the Earth’s sensitivity to a doubling of CO2 could itself be double that predicted by most climate models.

CO2′s significance

Dr Colin Summerhayes, who led the statement’s working group, says: “The climate sensitivity suggested by modern climate models may be fine for the short term, but does not encompass the full range of change expected in the long term…”

But he cautions that there are really two “sensitivities” involved: “Climate sensitivity is what happens in the short term in response to a doubling of CO2. But the Earth system sensitivity is what happens in the longer time frame as ice sheets slowly melt, and as sea level slowly rises.

“…The IPCC focuses on… the climate sensitivity – what will happen in the next 100 years. Earth system sensitivity tells you what happens in the next couple of hundred years after that.”

The GSL’s addition also reports new data showing that temperature and CO2 levels recorded in Antarctic ice cores increase at the same time. This, says Summerhayes, “makes the role of CO2 in changing Ice Age climate highly significant.”

Atmospheric carbon levels are currently just below 400 parts per million (ppm) – a figure last seen  between 5.3 and 2.6 million years ago. Global temperatures were then 2-3°C higher than today, and sea levels were several metres higher, due to partial melting of the Antarctic ice sheet.

If the current rate of increase (2 ppm per year) continues, CO2 levels could reach 600 ppm by the end of this century; levels which, says Summerhayes, “have not been seen for 24 million years”.

Models match palaeoclimate

The new GSL statement outlines evidence that a relatively modest rise in atmospheric CO2 levels and temperature leads to significant sea level rise, with oceans more acidic and less oxygenated. Previous such events caused marine crises and extinctions, with the Earth system taking around 100,000 years to recover.

Dr Summerhayes said: “We now have even more confidence from the geological record that the only plausible explanation for current warming is the unprecedented exponential rise in CO2 and other greenhouse gases.

“Recent compilations of past climate data, along with astronomical calculations, show that changes in the Earth’s orbit and axis cooled the world over the past 10,000 years. This cooling would normally be expected to continue for at least another 1,000 years.

“And yet Arctic palaeoclimate records show that the period 1950-2000 was the warmest 50 year interval for 2,000 years. We should be cool, but we’re not.”

He told Climate News Network: “The main implication from my perspective is that the geological record tells us that increasing CO2 increases temperature, melts ice, and raises sea level. This we know independently of any fancy numerical model run by climate scientists.

“However, those climate scientists’ models happen to come up with about the same answer as we get from the geological record, which suggests that the modellers  are likely to be on the right track.” – Climate News Network

Acid oceans harm more species

December 3, 2013 in Fish, Marine ecology, Ocean acidification

FOR IMMEDIATE RELEASE

A water melon sea urchin in Srdinian waters: Acid seas do not help larval digestion Image: Marco Busdraghi via Wikimedia Commons

A water melon sea urchin in Sardinian waters: Acid seas do not help larval digestion
Image: Marco Busdraghi via Wikimedia Commons

By Tim Radford

As climate change warms the world’s oceans, they are becoming more acidic. Researchers in Europe and the US have found the rising acidity is bad news for several species.

LONDON, 3 December – The chemistry of the oceans is changing. And it isn’t just the corals and the baby oysters that are unhappy. It makes juvenile rockfish really anxious, and it upsets the digestion of sea urchins.

The pH (a measure of acidity – the lower the pH, the more acid the water) of the planet’s oceans is dropping rapidly, largely because the carbon dioxide levels in the atmosphere are increasing. Since carbon dioxide dissolves in water to form carbonic acid, the seas are responding to global change.

The first and clearest victims are likely to be the corals, which are adapted to a specific value of pH in the oceans, but there have also been problems reported by oyster farmers.

Now Martin Tresguerres of the University of California, San Diego reports in the Proceedings of the Royal Society B that at least one species of juvenile fish responds badly to the changes in ocean chemistry.

There is a natural aspect to ocean acidification – submarine volcanoes discharge carbon dioxide and turn the deep seas around them to a kind of fizzing champagne, and upwelling ocean currents can occasionally deliver a stressful level of lower pH sea water to blight fishing waters.

But Tresguerres reports that he and colleagues subjected young Californian rockfish to the kind of water chemistry predicted as atmospheric carbon levels rise, and then measured their behaviour in response to changes of light in the aquarium, and to an unfamiliar object in the tank.

Stomach problems

What the researchers found was that the lower pH had a pronounced effect on one of the fish neuroreceptors linked to anxiety, and this effect lasted for at least seven days after the little creatures were returned to normal sea water. The change was not permanent: normal responses seemed to return after 12 days.

Meanwhile, across the Atlantic, Meike Stumpp of the University of Gothenburg in Sweden has been looking at how sea urchin larvae respond to altered pH in the seas. She and colleagues report in Nature Climate Change that they too tweaked the seawater chemistry, to discover that digestion took longer and was less effective, a bit of a problem for any young creature – especially one hardly a fifth of a millimeter in length – in the competitive world of the oceans.

“My measurements demonstrated a very strong pH dependency”, she said. “The enzymes in the sea urchins’ stomachs are optimised to function at very high pH – which is different from the situation in mammals, where stomach pH is acidic and enzymes work best at low pH.”

The implications are that as pH levels fall, life will become a great deal more problematic for at least some key marine species. And the likelihood of change is increasing. Scientists of the International Geosphere-Biosphere Programme  recently allotted a “very high” confidence level to a set of simple findings.

One was that humans were indeed making the seas more acidic, another was that the capacity of the oceans to absorb carbon dioxide would fall with increasing acidity, and a third was that the impact of this change in water chemistry would be felt for centuries. They also had “high confidence” that cold water corals and mollusc communities would be affected. – Climate News Network

UK waters grow cooler – and more acid

November 28, 2013 in Fish, Marine ecology, Natural Variability, Ocean acidification, Ocean Warming, United Kingdom

EMBARGOED until 0001 GMT on Thursday 28 November

Heading out... catches of Atlantic cod, and other cold water species, have halved Image: Peter from Edinburgh, Scotland, UK via Wikimedia Commons

Heading out… catches of Atlantic cod, and other cold water species, have halved
Image: Peter from Edinburgh, Scotland, UK via Wikimedia Commons

By Alex Kirby

A comprehensive report on the state of the seas around the United Kingdom says ocean acidification is probably increasing faster than for the last 300 million years.

LONDON, 28 November – Dipping your toes in the waters around Britain has grown marginally less inviting: in the last few years the seas have grown slightly colder.

Against the background of a continued warming trend, this blip is explained by scientists as an example of the climate’s tendency sometimes to go “off trend”, and to show clear variations from the norm.

UK researchers say the average UK coastal sea surface temperature in the last decade was lower in 2008-2012 than in 2003-2007, an example of short-term variability which they say is at odds with temperature records which “continue to show an overall upward trend“.

The finding – perhaps not surprising, given the slower pace of atmospheric warming in recent years – is reported by the Marine Climate Change Impacts Partnership (MCCIP) and is published in its latest Report Card, which assesses how climate change is affecting UK waters.

MCCIP, launched in 2005, is a partnership between scientists, the UK Government and its agencies, non-governmental organisations and industry.

Local consequences

For the first time the report looks at Arctic sea-ice coverage, and agrees that a long-term decline is clearly apparent, with sea-ice extent retreating and the ice becoming thinner as temperatures rise. It says the overall warming trend of recent decades is expected to continue.

It emphasises the importance of local-scale impacts, describing the movement of fish species and how non-native species are expanding their range.

It says: “International commercial landings from the north-east Atlantic of species identified as warm-adapted (e.g. grey gurnard, red mullet, hake) have increased 250% in the last 30 years, while landings of cold-adapted species (e.g. cod, haddock, whiting) have halved.”

The report also identifies a possible trend to smaller fish: “”Evidence is emerging that fish body-size is affected by climate change. For example, warm, lower-oxygen conditions favour smaller individuals, and by 2050 the average fish weight could be reduced by 14-24%.

Accelerating acidity

“However, there are multiple drivers of changes in size distributions including the known effects of fishing.”

One cause of change the report identifies with high confidence is growing ocean acidification. It says: “The current rate of increase in acidity… is probably more rapid now than any time in the last 300 million years.”

The researchers say changes to primary fish production are expected throughout the UK, with southern regions (for instance the Celtic Sea and English Channel) becoming up to 10% more productive and northern regions (like the central and northern North Sea) up to 20% less so.

But they acknowledge “some challenges” in identifying the impacts of climate change. These challenges are caused by difficulties in distinguishing both between short-term variability and long-term trends, and between climate influences and other pressures.

Over 150 scientists from 55 UK science organisations contributed to the report, which covers a range of 30 marine and coastal topics. The detailed peer-reviewed briefings on all the topics covered in the summary series are available online.  The 2013 Report Card and the 33 topic reports will be available online shortly after publication. – Climate News Network

Warming oceans will affect the poorest

October 22, 2013 in Climate, Forecasting, Marine ecology, Ocean acidification, Species loss, Warming, Weather

FOR IMMEDIATE RELEASE

A fisherman in Elmina, Ghana: Livelihoods are threatened by ocean warming. Image: Steve Evans via Wikimedia Commons

Livelihoods like this Ghanaian fisherman’s are threatened by warming oceans.
Image: Steve Evans via Wikimedia Commons

By Tim Radford

By 2100, the world’s oceans will be warmer and more acidic, with less dissolved oxygen and lower yields of fish and shellfish. And that will make life very difficult for up to 870 million of the world’s poorest people who rely on the sea for food, jobs and income.

LONDON, 22 October - Camilo Mora of the University of Hawaii and colleagues report in the journal Public Library of Science Biology that greenhouse gas emissions from industry and power generation have begun to trigger biogeochemical changes in the oceans that will impose huge costs.

These changes are likely to cascade through marine ecosystems and habitats to the deep ocean itself, and to affect humans along the way.

“The consequence of these co-occurring changes are massive – everything from species survival, to abundance, to range size, to body size, to species richness, to ecosystem functioning are affected by changes in ocean biogeochemistry,” said Dr Mora.

Mora and fellow oceanographers made headlines earlier this month by calculating the year in which any location on Earth was likely to experience dramatic and inexorable climate change: the researchers arrived at a mean date of 2047 (give or take six years on either side) for change, with the first impact in West Papua by 2020.

The PLOS Biology paperonce again tries to take a global view of change on the blue planet. The researchers calculated the effect of two scenarios for the future: one in which the world rapidly tries to reduce emissions, and the notorious business-as-usual scenario, which will take carbon dioxide concentrations to the unprecedented level of 900 parts per million by 2100.

No cooling

Then they contemplated the impact on 32 marine habitats and biodiversity hotspots, and then they examined the available data on human dependence on the ocean.

They found that most of the world’s ocean surface would feel the heat. Only in the polar regions would there be any increase in productivity or in oxygen levels. Nowhere would there be any cooling, and pH levels would trend towards acidification everywhere.

By 2100 global averages for the upper layer of the ocean would increase by between 1.2°C and 2.6°C. Dissolved oxygen concentrations would on average fall by between 2% and 4%, and phytoplankton production would diminish by between 4% and 10%. Phytoplankton are the base of the ocean food chain, so this can only reduce overall yield for between 470 and 870 million people who make a precarious and meagre living from the sea.

“The impact of climate change will be felt from the ocean surface to the sea floor,” said Andrew Sweetman, a co-author, now at the International Research Institute of Stavanger, Norway. “It is truly scary to consider how vast these impacts will be. This is one legacy that we as humans should not be allowed to ignore.” - Climate News Network