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Fish on acid lose fear of predators

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

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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

Whale dumps temper Antarctic warmth

March 25, 2014 in Antarctic, Carbon, Deep Ocean, Global Ocean Commission, Marine ecology, Whales

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Whales play a key part in recycling iron and carbon in the Antarctic Image: US National Oceanic & Atmospheric Administration

Whales play a key part in recycling iron and carbon in the Antarctic
Image: US National Oceanic & Atmospheric Administration

By Alex Kirby

By enriching the seas with iron expelled from their digestive systems, sperm whales are helping to slow the warming of the Antarctic, scientists say.

LONDON, 25 March – There is plenty yet to learn about the causes and effects of climate change, and here is one fact you may perhaps not have known until now: defecating sperm whales are helping to slow the warming of the Southern Ocean.

A team of Australian scientists and colleagues based at Flinders University in Adelaide reported in Proceedings of the Royal Society B (in 2010) that the whales help to increase levels of iron in Antarctic waters (which are iron-deficient).

Iron is important for marine life, and the polar oceans are important for helping to regulate atmospheric CO2 levels. So the whales’ personal hygiene is helping vastly smaller lifeforms to thrive, which in turn keeps the ocean ecosystem in balance and able to recycle carbon safely to the seabed.

Scientists had believed that the whales’ breathing decreased the efficiency of the Southern Ocean’s biological pump by returning carbon from the depths to the surface and thence to the atmosphere, where it would add to the greenhouse gases already there.

But the Flinders team says that by consuming prey in deep water (the whales search for squid  at 1,200 metres or even further down) and then releasing iron-rich liquid faeces into the sunlit zone near the surface, the whales instead stimulate new primary production and return the carbon to deep water.

Damaged by whaling

“Primary production” is the scientific term used to describe the minute forms of life produced by the effect of light in the presence of nutrients and – crucially – iron.

The researchers say Southern Ocean sperm whales stimulate the return of 40,000 tonnes of carbon annually to the deep ocean but breathe out only half that amount. So by stimulating new primary production, the 12,000 Antarctic whales act as a carbon sink, removing twice as much carbon from the atmosphere as they add by their breathing.

The team adds that the ability of the Southern Ocean to act as a carbon sink has been diminished by the large-scale killing of sperm whales during the era of industrial whaling, which reduced the global populations of many whale species to a fraction of their historic levels.

The researchers say the killing of the whales, by decreasing iron inputs to the surface zone, has had a serious impact. “This nutrient loss has undoubtedly altered the dynamics and food-web structure of these environments and this has decreased carbon export to the deep ocean”, they conclude.

Not unique

News of the researchers’ conclusions, which have so far gone largely unreported, was given to journalists covering a recent meeting in Hong Kong of the Global Ocean Commission by Professor Alex Rogers, of the Department of Zoology at the University of Oxford, UK.

Goodbye to all that? Whaling - still continuing in the Antarctic - disrupts the carbon recycling Image: Courtesy of the International Whaling Commission

Goodbye to all that? Whaling – still continuing in the Antarctic – damages the recycling process
Image: Courtesy of the International Whaling Commission

Asked by the Climate News Network whether the findings might apply to other whale species in other oceans, he said: “Not for iron, as the Southern Ocean is a high-nutrient low-chlorophyll area and thus primary production in this region is specifically limited by iron. In most other parts of the ocean it is limited by nitrates.”

But a similar paper had shown that before industrial whaling began whales had been the primary source of nitrates through the same process in Chesapeake Bay, on the US Atlantic coast. So fertilisation through defecation was likely to be a common mechanism, although different constituents of the faeces were important, and in the Antarctic krill might also be important in iron release.

Professor Rogers said whales made other useful contributions to human welfare. Taken together, the toothed whales – a group including sperm whales, belugas and narwhals – were thought to contribute 0.5-1.0% of all the energy needed  for ocean mixing. – 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

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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

Arctic melt speeding up

March 9, 2014 in Arctic, Climate Sensitivity, Deep Ocean, Greenland, Marine ecology, Ocean Warming, Polar ice, Solar energy

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Measuring the sun's reflectivity in the Arctic Image: NASA/Kathryn Hansen via Wikimedia Commons

Measuring the sun’s reflectivity in the Arctic
Image: NASA/Kathryn Hansen via Wikimedia Commons

By Tim Radford

It’s long been established that Arctic ice is on the retreat but it’s the pace of change that’s surprising scientists: latest studies show the region is at its warmest for 40,000 years. 

LONDON, 9 March - Ice in the Arctic continues to retreat. The season without ice is getting longer by an average of five days every 10 years, according to a new study in Geophysical Research Letters.  And in some regions of the Arctic, the autumn freeze is now up to 11 days later every decade.

This means that a greater proportion of the polar region for a longer timespan no longer reflects sunlight but absorbs it. This change in albedo – the scientist’s term for a planet’s reflectivity – means that open sea absorbs radiation, stays warmer, and freezes again ever later.

Warming accelerates

None of this is news: sea ice in the Arctic has been both retreating and thinning in volume for four decades. Researchers have tracked the retreat of the snow line to find tiny plants exposed that had been frozen over 40,000 years ago: the implication is that the Arctic is warmer now than it has been for 40 millennia.

This warming threatens the animals that depend for their existence on a stable cycle of seasons  and is accelerating at such a rate that the polar ocean could be entirely free of ice in late summer in the next four decades.

So Julienne Stroeve, of University College London and her colleagues have provided yet further confirmation of an increasing rate of change in the region in their latest study.

The scientists examined satellite imagery of the Arctic for the last 30 years, on 25 square kilometer grid, to work out the albedo of each square for every month they had data.

Their headline figure of five days is an average: in fact the pattern of freeze and thaw in the Arctic varies. In one region the melt season has been extended by 13 days, in another the melt season is actually getting shorter.

Energy increases

This increasing exposure to summer sunlight means that ever greater quantities of energy are being absorbed: several times the energy of the atomic bomb dropped on Hiroshima hits every square kilometer of the open Arctic Ocean.

“The extent of sea ice in the Arctic has been declining for the last four decades,” said Professor Stroeve, “and the timing of when melt begins and ends has a large impact on the amount of ice lost each summer.

With the Arctic region becoming more accessible for longer periods of time, there is a growing need for improved prediction of when the ice retreats and reforms in the water.” - Climate News Network

 

Climate technofixes ‘will not work’

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

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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

Cold and warm polar water mixing slows

March 4, 2014 in Antarctic, Convection, Deep Ocean, Ocean Warming, Polar ice

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A large iceberg calved from an Antarctic glacier: Weakening convection will make it slower to melt Image: NASA ICE (uploaded by russavia) via Wikimedia Commons

A large iceberg calved from an Antarctic glacier: Weakening convection will make it slower to melt
Image: NASA ICE (uploaded by russavia) via Wikimedia Commons

By Tim Radford

The process that sends cold surface Antarctic water to the warmer depths, redistributing heat and storing carbon, is now faltering, scientists say – because of climate change.

LONDON, 4 March – Global warming could have dramatic consequences for ocean circulation in the Antarctic, according to new research in Nature Climate Change. It could reduce convection in the Southern Ocean.

Convection is the process that turns over a vast body of sea water, sending the fresh water from melted ice to the depths, while bringing warmer, more saline waters to the surface. Since the ocean is part of the global machinery for redistributing heat and storing carbon, any change in the pattern of movement could have profound significance.

Casimir de Lavergne and colleagues from McGill University in Canada and the University of Pennsylvania in the US analysed a 60-year sequence of satellite observations and direct measurements in the Ross and Weddell seas and coupled these with simulated studies of ocean behaviour. They found that the surface ocean had become less saline: cold fresh water now forms a kind of lid on the Southern Ocean surface to trap warmer salt water below.

What had historically been an upwelling of warmer water had dramatic consequences for the Weddel Sea ice pack: in the mid-1970s it permitted a 250,000 square kilometre stretch of open water called a polynya that stayed open for three full winters before it closed. The polynya has not re-opened in 40 years.

While it was open, the cold, surface dense waters of the polynya sank 3,000 metres, and became new deep ocean bottom water, and this sinking, while it lasted, was on a massive scale: at least twice the flow of all the rivers of the terrestrial world.

For decades, oceanographers and glaciologists regarded the event as naturally rare, a curiosity rather than an important part of the ocean ecosystem. The latest study however presents a different picture.

Few escape opportunities

The first orbiting satellites may have recorded, for the first time in 1974, a regular but steadily weakening feature of the Southern Ocean, a phenomenon that was  weakening because of climate change. It also means that heat stored in the deep ocean has been unable to melt the wintertime icepack.

“Deep ocean waters only mix directly to the surface in a few small regions of the global ocean, so this has effectively shut off one of the main conduits for the deep ocean heat to escape,” said de Lavergne.

The team’s models showed that, before the Industrial Revolution, significant ocean convection occurred in the region. Under a high emissions scenario, the models showed a decrease in the strength of this convection. In seven of the team’s 25 computer models, deep circulation stopped entirely by 2030.

The team’s computer simulations also predict greater snow and rainfall in the Southern Ocean as atmospheric carbon dioxide increases.

“A warming planet will see dryer regions become dryer and wetter regions become wetter. True to form, the polar Southern Ocean – as a wet place – has indeed become wetter,” said Jaime Palter of McGill, a co-author. “And as a response to surface ocean freshening, the polynyas simulated by the models also disappeared.” – Climate News Network

US urges fishing ban in melting Arctic

February 24, 2014 in Adaptation, Arctic, Fish, Indigenous peoples, Marine ecology, Ocean Warming

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A US Coastguard vessel patrols the Arctic Ocean: Once the ice goes, the trawlers will not be far behind Image: PA1 Timothy Tamargo via Wikimedia Commons

A US Coast Guard vessel patrols the Arctic Ocean: Once the ice goes, the trawlers will not be far behind
Image: PA1 Timothy Tamargo via Wikimedia Commons

By Alex Kirby

Washington is urging countries that share the Arctic to ban commercial fishing in the offshore Arctic Ocean, something that will soon be possible for the first time in human history as the ice melts.

LONDON, 24 February – The countries that ring the Arctic Ocean will soon face a dilemma: can they risk commercial fishing fleets shooting their nets in those soon-to-be-ice-free seas?

Before long – quite possibly before mid-century – the Arctic Ocean will be free of ice during part of each summer, scientists are now saying confidently. For better or worse that will open up huge opportunities for shipping and hydrocarbon exploitation. And for the first time in recorded history it will allow the fishing boats access to whatever has lived undisturbed until now beneath the ice.

A three-day meeting began today in Nuuk, the capital of Greenland, where US officials are hoping to persuade the other nations which border the Arctic Ocean to introduce a moratorium on high seas fishing there (the other members of the group are Canada, Russia and Norway).

David Benton, of the US Arctic Research Commission (USARC), said the Americans were proposing an agreement “that would close the international waters of the Arctic Ocean to commercial fishing until there is a good scientific foundation on which to base management of any potential fishing”.

All coastal countries control fisheries within 200 miles of their own coastlines. The high seas beyond that limit belong to no country and can be protected only by international agreement.

Once the five Arctic nations have agreed a fishing moratorium, Benton said, they would then approach other countries with major commercial fishing fleets, such as China, Japan and Korea, to negotiate full protection for the central Arctic Ocean.

Previous ban

The Arctic was experiencing a fairly rapid rate of change, said Benton, as the permanent ice melted. “That’s potentially causing large changes in the ecosystem, but we don’t understand what’s going on up there. If we want to do things right, this is the approach we should be taking.”

In 2009, the US adopted its own Arctic Fishery Management Plan, closing American waters north of Alaska to commercial fishing until scientific research proves that the fishery is sustainable. Scott Highleyman, director of the international Arctic program for the Pew Charitable Trusts, said that had been a precaution that took account of the way warming was changing the Arctic ecosystem faster than science could keep up with it.

He told the Los Angeles Times: “There are no stock surveys or scientific assessments for fish there. You don’t want to fish a place where you don’t know the fish population dynamics. Any time we’ve done that, it led to catastrophic overfishing.” One example, Highleyman said, is the New England Atlantic cod fishery, which was shut down in the 1980s due to overfishing, costing 50,000 jobs.

An open letter to the Arctic governments, signed by 2,000 scientists from around the world, says that if the Ocean is overfished that will damage species that live there, including seals, whales and polar bears, and the people who use them for food.

“Until recently, the region has been covered with sea ice throughout the year, creating a physical barrier to the fisheries,” the scientists wrote. “A commercial fishery in the central Arctic Ocean is now possible and feasible.” – Climate News Network

Cat litter killer in the whales of the North

February 14, 2014 in Adaptation, Arctic, Atlantic, Disease, Ice Loss, Indigenous peoples, Marine ecology, Ocean Warming, Polar ice, Wildlife

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Blissful domesticity: But even domestic cats can spread Toxoplasma gondii

Blissful domesticity: But even domestic cats can spread Toxoplasma gondii

By Tim Radford

One consequence of a warming climate is new patterns of disease, and researchers have identified two parasites formerly unknown in the Arctic in marine mammals.

CHICAGO, 14 February – The great Arctic thaw – up to 50% of sea ice by area and 75% by volume in the summer season – could be offering new opportunities for one of the planet’s most successful parasites. Toxoplasma gondii, an infection spread by almost all cat species, has been identified for the first time in the western Arctic Beluga whale.

Toxoplasma is found almost everywhere that cats settle: domestic pets, ocelots, cougar, wild cats all carry and spread oocysts of the parasite (structures it uses to transfer to new hosts) in their faeces, to be spread further with discarded cat litter.

The parasite is notoriously hard to kill. Scientists store their samples in sulphuric acid, and the creature can survive unharmed in bleach. It is, however, routinely killed by freezing conditions, or boiling water.

The suspicion is that with the steady, sustained warming of the Arctic over the past 30 years, chiefly because of a buildup of carbon dioxide in the atmosphere, the retreat of the ice has begun to allow new traffic in parasite infections.

Another parasitic killer, a new strain called Sarcocystis pinnipedi, normally found only in the highest, iciest latitudes, has been linked with mass deaths too: 406 grey seals died in 2012 in the north Atlantic. It has also been observed to kill Steller’s sea lions, Hawaiian monk seals, walruses, grizzly bears and polar bears as far south as British Columbia.

In the case of Toxoplasma, warming polar summers could have created conditions in which the parasite could find new warm-blooded hosts further north. In the case of the second parasite, the loss of ice has meant a greater mixing of species, and allowed Sarcocystis to find new hosts in warmer waters.

Cause of blindness

“Ice is a major barrier for pathogens”, Michael Grigg, of the US National Institutes of Health told the American Association for the Advancement of Science annual meeting here. “What we are seeing with the big thaw is the liberation of pathogens gaining access to vulnerable new hosts and wreaking havoc.”

Toxoplasma can also infect people: it is the leading cause of infectious blindness in humans, and can be dangerous to unborn children and to people with compromised immunity.

It has been found in human communities in northern Quebec, perhaps spread by the consumption of dried seal meat. The discovery of Toxoplasma in Beluga whales has begun to worry health officials. Belugas are part of the traditional diet of the Inuit hunters of the far North.

Seals, walruses and polar bears are all what scientists like to call “ice obligate animals”: the ice sheet provides them with their preferred habitat. With the loss of the ice, new species are colonizing the Arctic, and those creatures that cannot now use the ice sheet have been forced to invade new habitats.

“Marine mammals can act as ecosystem sentinels because they respond to climate change through shifts in distribution, timing of their movements and feeding locations”, said Sue Moore of the US National Oceanic and Atmospheric Administration. “These long-lived mammals also reflect changes to the ecosystem in their shifts in diet, body condition and physical health.” – Climate News Network

Equatorial fish feel the heat

February 12, 2014 in Adaptation, Fish, Food security, Indonesia, Marine ecology, Ocean Warming, Warming, Wildlife

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Weaving through the coral: Small fish like these are important sources of food for larger reef species Image: D. Dixson

Weaving through the coral: Small fish like these are important sources of food for larger reef species
Image: D. Dixson

By Alex Kirby

Many species of fish living near the Equator are sensitive to variations in heat and will not thrive in the warmer oceans of the future, scientists in Australia have found.

LONDON, 12 February – Lying in a hot bath may be a pleasant experience, because you can always get out when you’ve had enough. For some of the fish that swim in equatorial seas, though, that is not an option: climate change threatens to make the water not just uncomfortable, but unendurable.

An international team of researchers based in Australia reports in Global Change Biology that the rapid pace of climate change is threatening the future of some of the fish which live near the Equator.

Over a 14-day period the team tested four species of damsel fish and two of cardinal fish. They say: “Our results indicate that low-latitude reef fish populations are living close to their thermal optima and may be more sensitive to ocean warming than higher-latitude populations.”

“Our studies found that one species of fish could not even survive in water just 3°C warmer than it lives in now”, says the lead author of the study, Dr Jodie Rummer from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) at James Cook University in Queensland.

Dr Rummer and her colleagues studied six common species living on coral reefs near the Equator. She says many species in this region experience only a very narrow range of temperatures throughout their lives, and so are probably adapted to perform best at those temperatures.

The world’s oceans are projected to warm by 2-3°C by the end of this century. “Such an increase in warming leads to a loss of performance”, Dr Rummer said. “Already, we found four species of fish are living at or above the temperatures at which they function best.”

Breeding compromised

The team measured the rates at which fish use oxygen across different temperatures – at rest and during maximal performance. The results showed that in warmer water fish lose their ability to perform properly. In the wild this would limit activities crucial to survival, such as evading predators, finding food, and finding the energy to breed.

With many of the Earth’s equatorial wild populations now living close to their thermal limits, there will be serious consequences if some – like the fish the researchers studied – cannot adapt to the speed at which the oceans are warming.

The response of many species to increasing warmth is to migrate to somewhere that suits them better, which could help to drain the equatorial oceans of fish which play a key role there. Dr Rummer suggests there will be declines in fish populations as species move away from the Equator to find refuge in areas with more agreeable temperatures.

“This will have a substantial impact on the human societies that depend on these fish,” she says. Many developing countries are in the equatorial zone, and fish are central to the livelihoods and survival of millions of people, including many in Indonesia and south-east Asia.

With rapid climate change, the scientists say, understanding the link between an organism and its environment is crucial to developing management strategies to conserve biodiversity and to allow the sustainable use of marine fisheries. This is especially urgent for ensuring food security for people. – Climate News Network

Trade winds draw ‘missing’ warmth to deep ocean

February 10, 2014 in Deep Ocean, Ocean Warming, Pacific Ocean, Trade Winds, Warming slowdown

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The trade winds make their mark on Hawaii - and they may explain where the "missing" warmth has gone Image: Richard B. Mieremet, Senior Advisor, NOAA OSDIA

The trade winds make their mark on Hawaii – and they may explain where the “missing” warmth has gone
Image: Richard B. Mieremet, Senior Advisor, NOAA OSDIA

By Tim Radford

Contrary to some reports, global warming hasn’t stopped or slowed at all, new research suggests. The trade winds have simply carried the heat into the Pacific Ocean – temporarily.

LONDON, 10 February – Australian and US scientists think they know where a lot of global warming has been concentrated: it has been tucked away below the surface waters of the western Pacific Ocean. And the agency that took the heat out of the atmosphere and transferred it into a liquid form could have been the equatorial trade winds.

Matthew England from the Australian Centre of Excellence for Climate System Science and colleagues report in Nature Climate Change that a dramatic acceleration in the winds has drawn heat from the atmosphere and transferred it to the ocean: cooler waters have risen to the surface to mask the transaction.

Climate sceptics – and some climate scientists – talk about a slowdown, or a pause, or a hiatus in global warming. In fact, temperatures have gone on rising and 13 of the 14 warmest years ever recorded have all occurred since 2000. But the rate of rise in global average temperatures since 2000 has not been as fast as the rate during the 1980s and 1990s.

Since greenhouse gas levels have continued to rise, and since scientists are sure of their atmospheric physics, then there was some “missing heat” to be accounted for.

Researchers have variously suggested that a puzzling increase in deep ocean temperatures could be one explanation or that perhaps the unevenness of temperature measurements around the planet might be another. But both suggestions were hypotheses: nobody had an answer that could be tested by any kind of experiment.

Slower rate

Professor England and colleagues worked with observed winds, surface air temperatures, and a set of ocean climate models to calculate what may have happened.

The global warming story has always been one of fits and starts: a warming that ought to have been observed 70 years ago stalled between 1940 and 1970, and when it resumed, did so in fits and starts. The overall trend continued upward, but the rate of rise slowed noticeably during the last decade.

Ocean circulation loops are driven by winds, and speed up as the winds intensify. Cool waters well up, warm waters descend. And intensify is just what the trade winds have done. They began strengthening during the 1990s, a process which continues today. Once the researchers added the trade winds to their calculations, the global average temperatures looked very like the observations during the hiatus.

They also found that four-fifths of the surface temperature cooling occurred after 2000, which confirmed that wind acceleration was the key contributor.

“Scientists have long suspected that extra ocean heat uptake has slowed the rise of global average temperatures, but the mechanism behind the hiatus remained unclear”, said Professor England.

Rapid rise on the way

“But the heat uptake is by no means permanent: when the trade wind strength returns to normal – as it inevitably will – our research suggests heat will quickly accumulate in the atmosphere. So global temperatures look set to rise rapidly out of the hiatus, returning to the levels projected within as little as a decade.”

The same mechanism could explain the slowdown between 1940 and 1970. In 1938, the British scientist G S Callendar argued that rising carbon dioxide levels should mean global warming but the evidence proved elusive, perhaps because the trade winds accelerated during those decades.

Richard Allan, professor of climate science at the University of Reading in the UK, said the current slowdown was only a temporary reprieve.

“Measurements from satellites and ocean buoys show that the planet is absorbing more heat than it is radiating out to space and the heat is building up in the oceans.

“This new research suggests that when the trade winds weaken again, the planet can expect rapid warming of the surface to resume, as greenhouse gas concentrations continue to rise.” – Climate News Network