Media release from McGill at AlphaGalileo
In the mid-1970s, the first available satellite images of Antarctica during the polar winter revealed a huge ice-free region within the ice pack of the Weddell Sea. This ice-free region, or polynya, stayed open for three full winters before it closed.
Subsequent research showed that the opening was maintained as relatively warm waters churned upward from kilometres below the ocean's surface and released heat from the ocean's deepest reaches. But the polynya -- which was the size of New Zealand -- has not reappeared in the nearly 40 years since it closed, and scientists have since come to view it as a naturally rare event.
Now, however, a study led by researchers from McGill University suggests a new explanation: The 1970s polynya may have been the last gasp of what was previously a more common feature of the Southern Ocean, and which is now suppressed due to the effects of climate change on ocean salinity.
The McGill researchers, working with colleagues from the University of Pennsylvania, analyzed tens of thousands of measurements made by ships and robotic floats in the ocean around Antarctica over a 60-year period. Their study, published in Nature Climate Change, shows that the ocean's surface has been steadily getting less salty since the 1950s. This lid of fresh water on top of the ocean prevents mixing with the warm waters underneath. As a result, the deep ocean heat has been unable to get out and melt back the wintertime Antarctic ice pack.
"Deep ocean waters only mix directly to the surface in a few small regions of the global ocean, so this has effectively shut one of the main conduits for deep ocean heat to escape," says Casimir de Lavergne, a recent graduate of McGill's Master's program in Atmospheric and Oceanic Sciences and lead author of the paper.
The scientists also surveyed the latest generation of climate models, which predict an increase of precipitation in the Southern Ocean as atmospheric carbon dioxide rises. "This agrees with the observations, and fits with a well-accepted principle that a warming planet will see dryer regions become dryer and wetter regions become wetter," says Jaime Palter, a professor in McGill's Department of Atmospheric and Oceanic Sciences and co-author of the study. "True to form, the polar Southern Ocean - as a wet place - has indeed become wetter. And in response to the surface ocean freshening, the polynyas simulated by the models also disappeared." In the real world, the melting of glaciers on Antarctica - not included in the models - has also been adding freshwater to the ocean, possibly strengthening the freshwater lid.
The new work can also help explain a scientific mystery. It has recently been discovered that Antarctic Bottom Water, which fills the deepest layer of the world ocean, has been shrinking over the last few decades. "The new work can provide an explanation for why this is happening," says study co-author Eric Galbraith, a professor in McGill's Department of Earth and Planetary Sciences and a fellow of the Canadian Institute for Advanced Research. "The waters exposed in the Weddell polynya became very cold, making them very dense, so that they sunk down to become Antarctic Bottom Water that spread throughout the global ocean. This source of dense water was equal to at least twice the flow of all the rivers of the world combined, but with the surface capped by freshwater, it has been cut off."
"Although our analysis suggests it's unlikely, it's always possible that the giant polynya will manage to reappear in the next century," Galbraith adds. "If it does, it will release decades-worth of heat and carbon from the deep ocean to the atmosphere in a pulse of warming."
The research was supported by the Stephen and Anastasia Mysak Graduate Fellowship in Atmospheric and Oceanic Sciences, by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery programme, by the Canadian Institute for Advanced Research (CIFAR) and by computing infrastructure provided by the Canadian Foundation for Innovation and Compute Canada.
Reference: 'Cessation of deep convection in the open Southern Ocean under anthropogenic climate change'; Casimir de Lavergne, Jaime B. Palter, Eric D. Galbraith, Raffaele Bernardello and Irina Marinov; advance online publication on Nature Climate Change's website March 2, 2014. http://dx.doi.org/10.1038/nclimate2132
Original story by Geoff Vivian, Science Network WA
Most mesopelagic species tend to feed near the surface at night, and move to deeper layers in the daytime to avoid birds. Pictured: The mesopelagic ‘ocean sunfish’ (Mola mola). Photo: Chris Zielecki
UWA Professor Carlos Duarte says mesopelagic fish – fish that live between 100 and 1000m below the surface – must therefore constitute 95 per cent of the world’s fish biomass.
“Because the stock is much larger it means this layer must play a more significant role in the functioning of the ocean and affecting the flow of carbon and oxygen in the ocean,” he says.
Prof Duarte led a seven-month circumnavigation of the globe in the Spanish research vessel Hesperides, with a team of scientists collecting echo-soundings of mesopelagic fish.
He says most mesopelagic species tend to feed near the surface at night, and move to deeper layers in the daytime to avoid birds.
They have large eyes to see in the dim light, and also enhanced pressure-sensitivity.
“They are able to detect nets from at least five metres and avoid them,” he says.
“Because the fish are very skilled at avoiding nets, every previous attempt to quantify them in terms of biomass that fishing nets have delivered are very low estimates.
“So instead of different nets what we used were acoustics … sonar and echo sounders.”
The findings have significant implications.
The sheer amount of biomass means they may respire about 10 per cent of primary production in deep waters.
Prof Duarte says research into the five ocean gyres, where vast amounts of flotsam collect, turned up surprising results.
“We actually called them oceanic deserts,” he says.
“They are not desert at all, they are very vibrant ecosystems that support a very high biomass.
“The largest fish stock in the ocean is not in the coastal areas … but actually in the central gyres of the oceans.
“The food web … in the central gyres of the ocean … it’s a lot more efficient than we thought.”
He says the survey also showed the oceans were healthier than previously thought.
“This very large stock of fish that we have just discovered, that holds 95 per cent of all the fish biomass in the world, is untouched by fishers,” he says.
“They can’t harvest them with nets.
“In the 21st Century we have still a pristine stock of fish which happens to be 95 per cent of all the fish in oceans.
“And that also changes our views on ocean health.”
Professor Duarte is the Director of the Oceans Institute at UWA in Perth, and also holds a post at the Mediterranean Institute for Advanced Studies, Spain, where he leads the Department of Global Change Research.
This article is based on an interview with Prof Duarte and the paper by lead author Prof Xabier Irigoien, who is director of the Red Sea Research Center at King Abdullah University of Science and Technology, Saudi Arabia.
University of Bristol press release
The cichlid fish Telmatochromis temporalis is found in Lake Tanganyika in East Africa
Competition may play an important role during the evolution of new species, but empirical evidence for this is scarce, despite being implicit in Charles Darwin’s work and support from theoretical studies.
Dr Martin Genner from Bristol's School of Biological Sciences and colleagues used population genetics and experimental evidence to demonstrate a role for competition that leads to the differentiation of new species within the highly diverse cichlid fishes of Lake Tanganyika in East Africa.
They found that the cichlid fish Telmatochromis temporalis shows two genetically distinct ecomorphs (local varieties of a species whose appearance is determined by its ecological environment), that strongly differ in body size and the habitat in which they live.
Dr Genner said: "We found large-sized individuals living along the rocky shoreline of Lake Tanganyika and, in the vicinity of these shores, we found small-sized individuals, roughly half the size of the large ones, that live and breed in accumulations of empty snail shells found on sand."
According to the study, the bigger fish outcompete the smaller ones, driving them away from the preferred rocky habitats and into the neighbouring sand, where the smaller fish find shelter for themselves and their eggs in empty snail shells.
“In effect, big and small fish use different habitats; and because of this habitat segregation, fish usually mate with individuals of similar size. There is virtually no genetic exchange between the large- and small-bodied ectomorphs,” Dr Genner commented.
Speciation occurs when genetic differences between groups of individuals accumulate over time. In the case of Telmatochromis there are no obvious obstacles to the movement and interaction of individuals. But, the non-random mating between large- and small-bodied fish sets the stage for the evolutionary play.
Dr Genner said: "The relevance of our work is that it provides experimental evidence that competition for space drives differential mating in cichlid fish and, in time, leads to the formation of new species. Nature has its ways – from body size differences to the formation of new species. And clearly, size does matters for Telmatochromis and for fish diversity."
The study was carried out by evolutionary biologists from the University of Bristol, the Natural History Museum London, the University of Kyoto and the Natural History Museum in Bern.
Reference
'Competition-driven speciation in cichlid fish' by Kai Winkelmann, Martin J. Genner, Tetsumi Takahashi and Lukas Rüber in Nature Communications
Original story at SBS
Hippocardia cunea: Rostroconchs are the only class of mollusks in the fossil record that are extinct today. They lived from the Early Cambrian until Late Permian as marine filter feeders partially buried in sediment. Source: Falls of the Ohio State Park
Lowly bottom-feeders survived the biggest mass extinction in history to rescue life in the world's oceans, a UK study has found.
Globally, the Late Permian extinction 252 million years ago wiped out 90 per cent of all marine species but creatures living on the sea floor fared better with almost 40 per cent surviving.
Scientists at the University of Plymouth made the discovery after compiling a database of 22,263 individual fossil marine invertebrates belonging to 1770 families of organisms.
The researchers worked out how each species moved, fed, and affected the ecosystem.
They learned that after the extinction, driven by volcanic eruptions and climate change, 38 per cent of benthic - or sea floor - life survived.
"Crucially, not one of the key ecological groups of animals that lived on or within the sea floor, and which keep ecosystems functioning, were completely eliminated," said lead scientist Professor Richard Twitchett.
Colleague William Foster said: "The fact that none of the key benthic ecological groups were completely eliminated globally during the biggest known extinction recorded in the fossil record was unexpected and demonstrates a certain level of resilience that had not been appreciated before."
The findings reported in the journal Nature Geoscience may help scientists better understand the fate of life in the oceans as a result of climate change today.
"We might predict that the present changes will not cause complete elimination of these key functional groups, unless future extinctions turn out to be more severe than that experienced 252 million years ago," said Mr Foster.
"However, our results also clearly show that some ecosystems do completely collapse, especially tropical ecosystems, in particular reefs."
Prof Twitchett said: "In this case, the global oceans in the extinction aftermath were a bit like a ship manned by a skeleton crew: all stations were operational but manned by relatively few species."
Original story by Andrew Darby, Sydney Morning Herald
Exhaustive: Jemima Stuart-Smith collects data for the first continent-wide survey of reef sea life which ended in Hobart. Photo: Rick Stuart-Smith
A year-long circumnavigation of Australia ended in Hobart on Wednesday with a trove of data from 700 coral and rock reef sites surveyed by volunteer divers for the Reef Life Survey Foundation.
It's not just over-fishing, it's the spread of invasive species.
Program co-founder Graham Edgar, of the University of Tasmania, said the first comprehensive study of any continent's reef systems found biodiversity losses, compared to earlier local counts.
''Virtually all of our coastline has had all the larger predatory organisms reduced - from the big fishes to the lobsters,'' said Professor Edgar, from the UTAS Institute of Marine and Antarctic Studies.
''It's not just over-fishing, it's the spread of invasive species and problems such as pollution when you get near metropolitan areas.''
His 14-metre catamaran Reef Dragon served as dive platform on a 12,000 nautical mile circumnavigation while 75 trained divers examined the life on reefs up to 400 nautical miles offshore. The odyssey took the divers from the pitch dark waters of Port Davey in south-west Tasmania to spectacular Osprey Reef, a sheer-walled coral atoll off far north Queensland.
Pioneering collections of biological information were made in the Coral Sea and off the North-West Shelf on the way down the West Australian coast and back to Tasmania, where Reef Dragon docked in a Derwent River marina.
Professor Edgar said the final report card was ''a mixed bag''.
''Some of the reefs are doing really well, particularly off the North-West Shelf where there are good numbers of large fish,'' he said. ''Elsewhere coral reefs are seriously degraded by bleaching. There have been some massive changes out of sight in the marine environment.''
Data collected on this, and other surveys, is making its way into what the New York Times said in an editorial this week was eye-opening work by Professor Edgar and other Tasmanian researchers.
According to a study published this month in Nature, the best protection for marine life comes in reserves that are likely to be ''no-take'', well-enforced, more than 10 years old, more than 100 square kilometres, and isolated by deep water or sand.
The New York Times said: ''Marine-protected areas are clearly a positive trend, a reflection of the growing awareness of governments across the globe that the oceans and their bounty are not limitless or indestructible.''
Australia's 3.1 million square kilometre system of marine reserves is in doubt after the federal government's decision to scrap most of the network's management plans and no-take zones. An expert scientific panel will examine the science behind the reserves, and advisory panels are to be chosen to improve stakeholder consultation.
Environment Minister Greg Hunt is yet to announce membership of the panels.
Original story by John Cook at The Conversation
Tony Abbott has pledged to help drought-stricken farmers while dismissing the link to climate change. Photo: AAP
Of course, heatwaves have happened in the past, including before humans started altering the climate. But it’s faulty logic to suggest that this means they’re not increasing now, or that it’s not our fault.
Sadly, this logical fallacy pervades the debate over heatwaves, not to mention other extreme events such as droughts, bushfires, floods and storms and even climate change itself. What’s more, we’re hearing it with worrying regularity from our political leaders.
First, the science. As the Climate Council has reported, hot days have doubled in Australia over the past half-century. During the decade from 2000 to 2009, heatwaves reached levels not expected until the 2030s. The anticipated impacts from climate change are arriving more than two decades ahead of schedule.
The increase in heatwaves in Australia is part of a larger global trend. Globally, heatwaves are happening five times more often than in the absence of human-caused global warming. This means that there is an 80% chance that any monthly heat record is due to global warming.
As the figure below indicates, the risk from heatwaves is expected to increase in the near future. Assuming our greenhouse gas emissions peak around 2040, heat records will be about 12 times more likely to occur three decades from now.
Increase in the number of heat records compared to those expected in a world without global warming. Image: Coumou, Robinson, and Rahmstorf
The impacts of heatwaves go a lot further than tennis players’ burnt bottoms. As we are now coming to realise, heatwaves kill more Australians than any other type of extreme weather. Floods, cyclones, bushfires and lightning strikes may capture more media coverage, but heatwaves are deadlier. On top of this comes new research linking heatwaves to increased rates of suicide.
Why are heatwaves increasing? Put simply, our planet is building up heat. Over the past few decades, our climate system has been building up heat at a rate of four Hiroshima bombs every second. As we continue to emit more heat-trapping greenhouse gases into the atmosphere, the warming continues unabated.
This is the point at which some people’s logic tends to go off the rails, distorting the science and insidiously distracting us from the risks. The reasoning is that as heatwaves have happened throughout Australia’s history, it follows that current heatwaves must also be entirely natural. This is a myth.
This is the classic logical fallacy of non sequitur – Latin for “it does not follow”. It’s equivalent to arguing that as humans died of cancer long before cigarettes were invented, it therefore follows that smoking does not cause cancer.
The non sequitur logical fallacy
This non sequitur is routinely used by Prime Minister Tony Abbott. He invoked it to deny that human-caused global warming was influencing bushfires (a phenomenon strongly influenced by heatwaves) and floods:
"Australia has had fires and floods since the beginning of time. We’ve had much bigger floods and fires than the ones we’ve recently experienced. You can hardly say they were the result of anthropic global warming."
Like a magician’s misdirection, this false argument distracts from the fact that the risk is increasing. Fire danger has been rising across many Australian locations since the 1970s. Fire danger days are happening not just in summer but also in spring and autumn.
Environment Minister Greg Hunt has followed the Prime Minister’s lead. The fact that Hunt used Wikipedia rather than scientific experts to inform his views caused many to overlook his logically flawed argument in downplaying the increasing risk from bushfires:
“I looked up what Wikipedia says for example, just to see what the rest of the world thought, and it opens up with the fact that bushfires in Australia are frequently occurring events during the hotter months of the year. Large areas of land are ravaged every year by bushfires. That’s the Australian experience.”
This week, Abbott reportedly denied the link between climate change and drought using the same fallacy:
“If you look at the records of Australian agriculture going back 150 years, there have always been good times and bad times. There have always been tough times and lush times and farmers ought to be able to deal with the sorts of things that are expected every few years.”
This argument overlooks the relationship between climate change and drought. Global warming intensifies the water cycle, making wet areas get wetter while drying other regions such as Australia’s south and east. Drier conditions, along with increased heatwaves, also drive the increase in bushfire danger.
Abbott doesn’t restrict his fallacies to extreme weather. Several years ago, he also presented the non sequitur to a classroom of schoolchildren, arguing that past climate change casts doubt on whether humans are now causing global warming:
“OK, so the climate has changed over the eons and we know from history, at the time of Julius Caesar and Jesus of Nazareth the climate was considerably warmer than it is now. And then during what they called the Dark Ages it was colder. Then there was the medieval warm period. Climate change happens all the time and it is not man that drives those climate changes back in history. It is an open question how much the climate changes today and what role man plays.”
This flies in the face of decades of peer-reviewed research. My colleagues and I have found that among climate research stating a position on the causes of global warming, more than 97% endorse the consensus that humans are responsible.
It is greatly concerning that Australian policy is being dictated by science-distorting false logic. The science is sending us a clear message: human-caused global warming is increasing the risk of heatwaves as well as other extreme weather events such as floods, drought and bushfires. We need to look this problem square in the face, rather than have our attention misdirected.
John Cook created and maintains the Skeptical Science website
This article was originally published on The Conversation.
Read the original article.
Original story by Geoff Spinks, University of Wollongong at The Conversation
The humble fishing line. Photo: Flickr/derfian
In our case, we spent nearly two decades developing exotic materials as artificial muscles – to now show in a paper published in Science today that the best performing systems can be made from ordinary, everyday fishing line.
Or sewing thread, if you prefer.
Not only are these materials cheap and readily available, they can be converted into high performance artificial muscles easily – just start twisting!
Polymer coil muscles.
We attached one end of the fishing line to an electric drill and hung a weight off the other to apply some tension. We stopped the weight from rotating as we used the drill to twist the fibre.
At first the twisted fibre shortened but maintained a uniform shape. But at a critical point, a loop or coil formed in the fibre and further twisting produced more coils. Before too long the whole fibre was a spring-like coil.
To set this shape we applied a little bit of heat using a hairdryer and let it cool. If we then hung a weight off the polymer coil and applied some more heat, the coil contracted.
For more convenience and better temperature control, we wrapped a conductive material around the fibre and applied heat by passing a current.
The amount of contraction and the force generated can be impressive and in most respects compare favourably with our own muscle.
In one example, we used a 16cm length of coiled Nylon-6 fishing line 0.86mm in diameter to lift a 500g weight about 20mm in 2 seconds.
A similar sized natural muscle would also contract about 20mm in slightly shorter time (~1 second) but lifting only 150g.
Comparing ‘muscles’ made by coiling (from top to bottom) 2.45mm, 0.86mm, 0.28mm and 0.15mm Nylon-6 monofilament fibres. Photo: Science/AAAS
By optimising our coil structures we can easily achieve 50% or more contraction in length and increase contraction speed to 7.5Hz.
Our polymer coil muscles also last a long time – we gave up testing after 1.2 million cycles where the muscle reversibly contracted 10% in length in 1 second per cycle.
One application that we are pursuing with the polymer coil muscles is in our massage sleeve designed to reduce the effects of lymphoedema, a condition that affects around a third of women diagnosed with invasive breast cancer.
Lymph sleeve animation.
Breast cancer‐related lymphoedema (BCRL) is the swelling of the arm caused by the build-up of lymphatic fluids and leads to heaviness, swelling and discomfort for patients.
Massage is an effective treatment and the “lymph sleeve” is meant to be worn by BCRL patients during their daily lives. The lightweight actuating fabric will detect swelling and then respond by “squeezing” the arm to enhance lymph flow.
The discovery of the polymer coil muscles is the outcome of more than five years of collaborative effort from researchers around the world.
The work started with the discovery by University of Wollongong PhD student (and now ARC Discovery Early Career Researcher Award Fellow) Javad Foroughi of a “torsional” type of actuation movement in electrochemically charged carbon nanotube yarns.
Subsequently, our collaborators at the University of Texas at Dallas (UTD) – who make the yarns – also found that similar torsional actuation response could be produced by filling the yarn pore volume with candle wax to make hybrid yarn muscles.
Heating the wax generated the torsional or twisting movement. It was also observed that overtwisting these yarns generated coils and that these coils contracted by up to 10% in length when the wax was heated.
At that stage we did not know why the coiling amplified the length-wise tensile actuation.
But our most recent collaboration has revealed more on the coupling between the torsion and the coil contraction by applying the mechanics theory that had been developed for more than a century and applied to helically-coiled springs.
Finally, we also discovered that similar effects occur in highly oriented polymer fibres when they are twisted into coils.
The pathway to discovery was by no means obvious. If we had not been investigating exotic materials – such as carbon nanotubes – then we would not have observed the very large torsional actuation in these materials.
That work led us to investigate further the effect of twist and the discovery of overtwist-induced coiling. From there we were able to produce high performing contractile muscles from both overtwisted carbon nanotube yarns, and more recently, ordinary polymer fibres like fishing line.
While it’s impossible to predict what the next breakthrough will be, we do know the areas where improvements are needed.
Efficiency is well below that of muscle. Approximately 20% of the input chemical energy for muscle is converted to mechanical work.
Our muscles convert about 2% of electrical heat energy to muscle work, similar to shape memory alloys.
We would also like to use stimuli other than heat and our preliminary work has shown that movement is possible with light or chemical agents.
Geoff Spinks receives funding from the Australian Research Council.
This article was originally published on The Conversation.
Read the original article.
Media release from UQ News
Scientists document the temperature of soil, one layer above permafrost. Photo: Dr Virginia Rich, University of Arizona.
UQ's Australian Centre for Ecogenomics researcher Ben Woodcroft said the methane-producing micro-organism, known as a ‘methanogen’, was thriving in northern Sweden’s thawing permafrost in a thick subsurface layer of soil that has previously remained frozen.
Mr Woodcroft said no one knew of the microbe’s existence or how it worked before the research discovery.
He said global warming trends meant vast areas of permafrost would continue to thaw, allowing the microbes to flourish in organic matter and drive methane gas release, which would further fuel global warming.
“The micro-organism generates methane by using carbon dioxide and hydrogen from the bacteria it lives alongside,” Mr Woodcroft said.
Lead researcher and UQ’s Australian Centre for Ecogenomics Deputy Director Associate Professor Gene Tyson said the findings were significant.
“This micro-organism is responsible for producing a substantial fraction of methane at this site,” he said.
“Methane is a potent greenhouse gas with about 25 times the warming capacity of carbon dioxide.”
The researchers showed the organism and its close relatives live not just in thawing permafrost but in many other methane-producing habitats worldwide.
The team made the discovery by using DNA from soil samples and reconstructing a near-complete genome of the microbe, bypassing traditional methods of cultivating microbes in the lab.
The ‘Discovery of a novel methanogen prevalent in thawing permafrost’ research is published here in the journal Nature Communications.
PhD candidate Rhiannon Mondav who is student of UQ and Uppsala University based in Sweden, co-authored the paper alongside ACE researchers and international collaborators.
The work was funded by the United States Department of Energy Office of Biological and Environmental Research’s Genomic Science Program and the Australian Research Council.
Media: ACE Deputy Director Associate Professor Gene Tyson, 07 3365 3829,g.tyson@awmc.uq.edu.au or UQ Faculty of Science Communications Officer Monique Nevison, 07 3346 4129, m.nevison@uq.edu.au.
Original story by Ross Large, University of Tasmania at The Conversation
Slime on Earth… that’s all there was for a billion years. Photo: www.shutterstock.com
During the middle years of Earth’s history (1.8 billion to 800 million years ago), evolution stagnated. Life remained as little more than a layer of slime for a billion years. This period has become known as the “boring billion” years.
So what was going on? A research team led by geologists at the University of Tasmania has developed new mineral technology to track the trace metal content of the ocean and oxygen content of the atmosphere over the past 3.5 billion years. This has never been achieved before.
Why is it important? Evolution of life in the oceans is strongly influenced by trace metals, as many metals (such as copper, zinc, cobalt and selenium) are taken up by marine species and are critical for life and evolutionary change.
Our UTAS research team – of which I was a part – with help from many other international geologists, have been collecting seafloor sediments from all around the world over the past six years.
Ross Large and Valeriy Maslennikov (from the Russian Academy of Science) on location in Siberia. Photo: Ross Large
We found pyrite (iron sulfide) in each sample and analysed for 22 different trace metals with a cutting edge laser system at UTAS, and built a unique database of more than 3,000 pyrite laser analyses to track changes in ocean chemistry spanning a 3.5-billion-year period through time.
Some exciting and totally unexpected outcomes emerged from this ocean tracking technology. The most significant outcome relates to how trace metals in the oceans have influenced the evolution of life.
Back in the early part of Earth’s history, from 3.5 billion to 1.8 billion years ago, single celled life evolved slowly but progressively, related to an abundance of available trace metals in the oceans. But during the “boring billion”, from 1,800 million to 800 million years ago, evolution slowed. This has been a puzzle to scientists.
Our research, published in the Earth and Planetary Science Letters, suggests that the reason for the slow down is that the trace metal content of the oceans declined. This resulted in a depletion of critical trace metal nutrients to the point that oxygen content dropped and life in the oceans was in great danger of total collapse.
But rather than causing a mass extinction, marine life and evolutionary change was put on hold for a billion years.
Following the boring billion, our research shows that the trace metal content in the oceans rose steeply in a series of steps over a 200-million-year period, from 750 million to 550 million years ago.
This was accompanied by a steep rise in oxygen in the atmosphere (known as a Great Oxidation Event, see below) that led to the Cambrian explosion of life and progressive evolution to the present time.
Bio-essential trace elements are critical to life and evolution. These include cobalt, selenium, copper, zinc, molybdenum, vanadium and cadmium. Certain species need these trace elements to survive.
The elements are linked into the chemical structure of the cells and become a natural nutrient for survival. Cobalt is a central atom in the structure of vitamin B12, whereas zinc is essential for growth in many species.
The UTAS research team showed that at certain periods of earth history these trace elements were in short supply (such as the boring billion period) leading to evolutionary decline, whereas in other periods the bio-essential elements were in great abundance, causing rapid evolutionary change.
The Cambrian explosion was the relatively rapid appearance, around 542 million years ago, of most major animal phyla, as demonstrated in the fossil record.
Fossil tracks form the Cambrian explosion. Photo: Flickr/Maitri
This was accompanied by major diversification of other organisms. Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organised into colonies.
Over the following 70 million or 80 million years, the rate of evolution accelerated by an order of magnitude and the diversity of life began to resemble that of today.
The Cambrian explosion has generated intense scientific debate. The seemingly rapid appearance of fossils in the “Primordial Strata” was noted as early as the 1840s. In 1859 Charles Darwin discussed it as one of the main objections that could be made against his theory of evolution by natural selection.
The long-running puzzlement about the seemingly abrupt appearance of the Cambrian fauna 540 million years ago centres on three key questions:
This latest research by the UTAS team demonstrates, for the first time, a rapid increase in bio-essential trace elements in the ocean starting 660 million years ago. So was this the cause of the Cambrian explosion of life?
GOEs are large increases in oxygen in the Earth’s atmosphere and there have been two in Earth’s history – one at 2.4 billion to 2.5 billion years ago and one at around 700 million to 550 million years ago corresponding with the Cambrian Explosion.
There are several schools of thought about GOEs' origin. The most favoured theory is that the GOEs are produced by a dramatic increase in ancient marine organisms (cyanobacteria) that released oxygen as a by-product of photosynthesis.
But which came first? Did the increase in oxygen speed up evolution of life or did an increase in life result in a rapid rise in atmosphere oxygen?
Either way, the oxygen did eventually accumulate in the atmosphere, providing a new opportunity for biological diversification as well as tremendous changes in the nature of chemical interactions between the atmosphere, rocks, oceans and living organisms.
The research team at UTAS, using a novel approach to the problem, demonstrated major changes in trace element concentrations in the ocean at both GOEs, which may be the answer to the rapid expansion of life.
This is the start of a new journey for the Tasmanian research team and we will be doing much more with this technology.
But it’s already becoming clear that there have been many fluctuations in trace metal levels over the millennia and these may help us understand a host of events including the emergence of life, fish, plants and dinosaurs, mass extinctions, and the development of seafloor gold and other ore deposits.
Ross Large receives funding from Australian Research Council and Australian Mineral Industry Research Association.
This article was originally published on The Conversation.
Read the original article.