Australasian Science: Australia's authority on science since 1938

Exclusive news for subscribers

By Stephen Luntz

Subscribe for complete access to all news articles, columns and features each month.

Groundwater Warnings Visible from Space

Trees can provide warnings that groundwater is being overexploited, and this generally occurs when water levels are pushed to more than 10 metres below the surface.

“All across Australia there are vast tracts of woodland, forest and riparian vegetation that depend on groundwater for survival, particularly during drought,” says Prof Derek Eamus of the National Centre for Groundwater Research and Training. “We know that if we extract too much water from under these ecosystems, there is a good chance the trees will die. But until now we didn’t know clearly what the cut-off was – how much water you can take before it adversely affects the forest that depends on it.”

Eamus measured the girth and leaf area of trees and found that “up to a groundwater depth of 6–9 metres the forest does fine, the trees grow well and develop thick trunks and heavy leaf canopies. The diversity of tree species is high.” However, tree health is affected once the water table falls below 10 metres, even if some roots reach to this depth.

Satellites have been used to produce enhanced vegetation indices and measurements of leaf area, both of which track a drought’s progress over large areas. Eamus suggests these could be used to see where groundwater is getting dangerously low. “It also means that anyone who is doing the wrong thing and extracting too much water can be spotted from space, being ‘dobbed in’ by their trees – and this is likely to become as regular a part of water management as speed cameras are for traffic management.”

Joshua Dean, a PhD student at La Trobe University, has added to this work by revealing that groundwater studies can lead to better positioning of timber plantations. “Growing timber plantations intercept a lot of rainfall that could have otherwise recharged our groundwater aquifers,” says Dean.

“Recharge of water to our aquifers is not consistent across a landscape. Most of it takes place in very specific areas. If we can identify where this occurs in different types of landscapes, then we know where we can put plantations to minimise their effect on our water.”

As a demonstration, Dean recommends placing plantations on the upper slopes in Victoria’s Grampians, as most groundwater recharge occurs further down.

Coal Seam Gas Leak Study Undermined

A study of atmospheric methane in the Tara gas fields of southern Queensland has cast doubt on the industry’s claims to a clean environmental record (see p.3). With coal seam gas (CSG) already highly controversial, the study has had the unusual distinction of being attacked by both a lobby group and a federal minister.

Atmospheric methane levels average 1.8 ppm, although this can rise in the vicinity of sources of methane such as wetlands. “In Tara the concentrations are consistently higher than 2 ppm and approach 7 ppm in a few locations,” says Dr Damien Maher of Southern Cross University’s Centre for Coastal Biogeochemistry Research.

Maher, an expert on the estuarine carbon cycle (AS, Jan/Feb 2013, p.11), adds that there are few wetlands in the area, and a shortage of other biological sources. He notes: “These results are higher than values reported for conventional gas production fields in Siberia, one of the world’s largest natural gas production areas.”

Moreover, the isotopic ratio of the methane detected in the area is similar to the ratio measured in the coal seams but different to methane produced by bacteria, suggesting that the gas is a result of leakage.

Maher acknowledges, however, that the findings do not prove that mining is responsible. “Any geological area that has gas deposits is going to have natural seeps,” he says. “At this stage we are unable to separate the contribution of CSG activities from natural seeps because no sampling was done in Tara prior to mining.”

The same point was made by Prof Mark Tingay of the Australian School of Petroleum Science at Adelaide University (AS, Jan/Feb 2013, p.37) who warned: “People need to be very cautious about this result”.

Nevertheless, Maher measured atmospheric methane at normal rates in the Richmond River catchment area, where CSG exploration is taking place but mining has not begun.

The CSG industry claims a largely harmless leakage rate of 0.12% based on a US study. However, contested studies in the US have estimated rates as high as 8%. Methane has 25 times the warming capacity of carbon dioxide.

The measurements were conducted with a cavity ring-down spectrometer, which is capable of measuring atmospheric and water impurities to parts per billion. Such devices are not new, but the Picarro analyser Maher used is the first in Australia to be able to detect carbon dioxide and methane concentrations and isotope ratios at the same time.

Maher’s work has been submitted for publication, but peer review is still underway. In the meantime Maher and colleague Dr Isaac Santos have made a submission to Department of Climate Change and Energy Efficiency and presented their work at a public lecture.

Maher and Santos were attacked by the Australian Petroleum Production & Exploration Association (APPEA) and the federal minister for mining Martin Ferguson, both of whom criticised the quality of the work and the decision to discuss it prior to publication.

Southern Cross University has stood behind its researchers, with its Vice Chancellor, Prof Peter Lee, defending the quality of the researchers and the decision to discuss their work while waiting for the often lengthy peer review process to take place. Lee also accused the APPEA of inaccuracies and misleading behaviour.

Maher is keen to continue work on what he sees as unanswered questions. He hopes to get baseline measurements of methane emissions before mining starts in an area, and then compare these with what occurs once it has begun. He is also using atmospheric models to estimate the flux of methane required to produce the measured concentrations.

Cream May Treat Melanoma

A cream has been developed that could offer a painless treatment for melanoma, although the inventor cautions it is a long way from clinical use.

“Australia has the highest incidence of melanoma in the world, with more than 11,000 new diagnoses each year,” says Dr Taghrid Istivan of RMIT’s Health Innovations Research Institute. “Currently the only effective treatment for early-stage melanoma is surgery to cut out the tumour and healthy skin surrounding the affected mole.”

However, a virus capable of killing melanoma cells has been demonstrated in the lab, and Istivan has built on this discovery. “The virus has many proteins in it, one of which is thought to be linked to killing cancer cells. We created a very small protein, or peptide, that mimics this behaviour and put it into a cream. The peptide we have developed is toxic to melanoma cells but leaves normal skin cells unaffected.”

By synthesising just the effective component of the virus, Istivan hopes her product will be “more cost-effective” while also avoiding the danger that the virus might mutate and kill healthy cells.

Istivan stresses she has yet to even secure funding to advance her work to clinical trials, and the people calling her and asking where they can buy the cream are jumping the gun. Nevertheless, if the peptide proves effective it will eliminate the cost of producing a large and expensive virus protein as well as the inevitable damage to healthy cells from surgery to remove melanomas.

Even if clinical trials meet with success, Istivan warns that the cream can only be expected to work against the early stages of melanoma, before metastasis has occurred.

Zinc Slows Box Jellyfish Toxin

American researchers have determined the mechanism behind Australian box jellyfish poison, and found a way to inhibit its activity.

Australia’s reputation as the home of the deadliest venoms is greatly enhanced by the presence of Chironex fleckeri, whose tentacles contain arguably the most potent poison of any animal. The jellyfish inhabits mangroves as far north as Vietnam, and its range appears to be expanding.

Stings from the 2-metre tentacles cause painful skin legions, and in some cases rapid death from heart failure, but until now the nature of the toxin and its mechanism have been unknown.

A/Prof Angel Yanagihara and Prof Ralph Shohert of the University of Hawaii revealed in PLoS One that, in Yanagihara’s words, “a previously dis-regarded haemolysin can cause an avalanche of reactions in cells. This includes an almost instantaneous, massive release of potassium that can cause acute cardiovascular collapse and death.”

Zinc can block the effects of bacterial poison. When Yanagihara and Shohert injected mice with jellyfish venom equivalent to a human being stung by 2.5 metres of tentacle, 90% died within 23 minutes. However, if the mice had been given zinc gluconate, potassium release decreased and survival time more than doubled.

Strangely, when zinc was applied after envenomation the improvement was even greater.

Ciguatera Toxin Increases Pain Response

The nerve pathway that causes the most distinctive symptom of ciguatera poisoning has been identified.

Ciguatera poisoning occurs when tropical fish eat dinoflagellates attached to coral or algae. The fish convert progenitor molecules into ciguatoxins that accumulate as larger fish eat smaller ones. Dr Irina Vetter of the University of Queensland Institute of Molecular Bioscience says the toxins do not appear to affect the fish – at least “not the way they do humans”.

While symptoms can include joint pain, nausea and hallucinations, the most prominent is described as an extremely painful burning sensation when exposed to cool objects.

There is no cure for ciguatera, and the effects can be debilitating for months. The frequency appears to be rising as a result of increasing damage to coral reef systems (AS, Nov 2012, p.11), and the causes of the symptoms have been debated for many years.

Vetter and her colleagues developed a new model that allowed them to replicate and quantify ciguatera symptoms for the first time. “The problem in pain research is we lack words to adequately describe experiences. We call it a burning pain, but you can tell cool objects apart from hot ones,” says Vetter.

“We identified the channels in the nervous system the ciguatoxins act on, which in turn activate the nerves that sense cold and pain,” says Vetter. “It’s the first time anyone has established the molecular and cellular basis of ciguatoxin-induced cold pain.”

Vetter says we have multiple ion channels triggered by chemicals such as menthol and mustard. Rather than triggering the pain pathways directly, ciguatoxins increase the excitability of pain-sensing nerves so that moderately cool temperatures trigger responses that might be expected from exposure to freezing cold.

“At 15ºC the contribution from the mustard oil channel is normally very minor,” says Vetter. “With ciguatera poisoning the excitability threshold has shifted to much higher temperatures so you get signalling from pain-sensitive neurons.”

Vetter admits that “we really don’t know” what, if any, evolutionary basis exists for the poisoning, and whether the dinoflagellates benefit in any way from the toxins.

No drugs exist to target the mustard oil channel, but Vetter says “several are in development” for other conditions, and it is hoped these may bring sufferers some relief. Vetters says: “We now know we have two possible targets, either the increased nerve excitability in general, or the mustard oil channel.”

Memory to the Four

A famous paper claiming that seven is a “magical number” for human memory may have been far too flattering, Prof Gordon Parker of the University of NSW School of Psychiatry has argued in the journal Acta Psychiatrica Scandinavia.

In 1956 George Miller published a paper in Psychological Review called “The Magical Number Seven, Plus or Minus Two. Some Limits on Our Capacity for Processing Information”. Miller’s work remains one of the most commonly cited psychological papers of all time, but Parker argues this has more to do with the quality of his writing and cultural references than the evidence Miller produced.

Miller’s work has since been challenged by Prof Nelson Cowan of the University of Missouri, who found that subsequent studies showed most people are only able to immediately recognise up to four objects, and struggle to process more than four bits of information in their short-term memory. “So to remember a seven-numeral phone number, say 6458937, we need to break it into four chunks: 64 58 93 7. Basically four is the limit to our perception,” says Parker.

Parker found that even the evidence Miller relied on to support his conclusion was doubtful, with a substantial drop-off in capacity above four items. Yet when he questioned his research assistants all of them were familiar with the Miller paper, while none had heard of Cowan’s work.

If learning our numerical capacity has been slashed by almost half is not bad enough, Parker agrees that many people prefer to break phone numbers into three, and says there “seems to be a generational effect here”. He says it is possible information technology is rewiring our brains to make a new generation capable of remembering one less digit than the last.

Parker says he was told to restrict lectures to three key points, but wonders if there is room to squeeze in one more.

Bowerbirds Refuse Assistance

Male bowerbirds prefer to stick to un-successful strategies to attract mates, even when given assistance towards more promising paths.

Prof John Endler and Dr Laura Kelley, both of Deakin University’s Centre for Integrative Ecology, previously revealed that female great bowerbirds prefer bowers where stones and bones are arranged in geometrical fashion, with the smallest lying towards the female (AS, June 2012, pp.30–32). This creates a depth illusion, and male bowerbirds accommodated the females by creating suitably laid out bowers.

Great bowerbirds can take 5 years to build their bowers and spend 25 years improving them. However, some males are better at structuring their bower courts than others. “We know from our previous research that the quality of the visual illusion the males create with the objects in their bowers predicts their likelihood of attracting a mate,” says Endler.

Endler and Kelley pondered what would happen if they improved the bowers of unsuccessful males. Would the males “maintain the display at the new higher level, decrease the perspective quality back to its original quality, or allow it to decay at random over time? We found that the original perspective was actively recovered to individual original values within 3 days.” They report in Proceedings of the National Academy of Sciences that the males’ reward for restoring their less illusionary bowers was an ongoing lack of mating success.

Particularly puzzling was that the males did not always restore objects to the exact locations from which the researchers had moved them. However, each object was restored to a similarly forward or rear location, even if this was inappropriate for its size, while the left/right positioning was not similarly conserved.

“The males really care about their consistent pattern, even if it is a poor one,” says Endler.

The evolutionary basis for the illusion remains a mystery, making it particularly difficult to explain the stubbornness of what Endler calls “inferior males”. Endler has not been able to conduct longitudinal studies to see if the badly designed bowers are a phase the young males go through.

Endler says parallel studies in other species are hard to find, since most forms of sexual display involve intrinsic characteristics that researchers would find harder to modify. However, women who have tried to coax potential boyfriends into tidying their bedrooms might think that, in one species at least, the data is already in.

Powdered Ethylene Aids Fruit Transfer

The transportation of fruit may become easier and cheaper as a result of the production of a powder that releases ethylene gas.

Many fruits are now picked while they’re still green and hard in order to make transportation easier. They are then ripened with ethylene gas.

Ethylene is a hydrocarbon produced by plants to trigger ripening and the shedding of fruit or leaves. Its release is the reason a ripe banana peel can trigger many other fruits to ripen.

Ethylene at concentrations of a few hundred parts per million is used over 24–48 hours to stimulate ripening in fruit prior to sale. However, compressed ethylene gas is highly flammable, and explosive accidents have occurred with canisters.

“We have been looking at methods to encapsulate the gas in various types of solid materials to create a safe and convenient powder form,” says Prof Bhesh Bhandari of the University of Queensland’s School of Agriculture and Food Sciences. The work has now succeeded, with the production of a starch derivative that stores ethylene in cavities within its crystal structure and then releases the gas when the temperature and humidity are raised.

Bhandari denies any significant environmental effects at the concentrations being used, and ethylene is too reactive to last long enough in the atmosphere to be a significant greenhouse gas.

He suggests the powder could be applied to fruit while in transit, rather than at storage depots – as is the case with pressurised gas.

“We have lodged a patent,” says Bhandari.

Physics Plan for the Decade Ahead

The Australian Academy of Sciences has released a decadal plan for physics.

“Over the next decade there will be rapidly increasing opportunities to harness physics to serve our society in generating and managing electricity, improving medical diagnostics and therapy, climate change mitigation and much more,” said Academy Vice President and Secretary for Physical Sciences, Prof Chennupati Jagadish. “The Physics Decadal Plan provides a roadmap towards a vibrant future; it makes strong recommendations to help Australia make the most of the new quantum revolution and the quest for new physics.”

The plan identifies four critical issues:

• achieving a physics-literate workforce and community;

• realising human capital in physics;

• building on physics research and investment; and

• engaging in the international enterprise of physics.

The plan also highlights what it sees as the key opportunities for Australian physics in quantum computing and related fields, the quest for “new physics and new symmetries” and the capacity of physics to serve society in areas such as clean energy generation.

The President of the Australian Institute of Physics, Dr Marc Duldig, said: “The plan is not something that will get government endorsement. It has no budgeting or dollar values. It is a process rather than a wish list, setting out the things we need to address to maintain a technological society.”

Central features of the plan, such as the need for school physics to be taught by people who have studied the science at university, represent longstanding concerns among scientists. However, Duldig says: “The second volume has the evidentiary base on which the plan is made, documenting the reduction in the number of students studying physics and the ageing of the academic community. This will be of value to governments, providing them with data, not just anecdotal evidence.”

Other fields of science have been releasing decadal plans, but physics has lagged. However, Duldig anticipates that regular plans will be developed from now on.

While the plan identifies a need for more physicists to replace retiring academics and to provide a greater skill base for schools, Duldig believes we have enough people to do both if we can retain graduates. “The problem is that the teaching profession is not seen as being as important as we think it should be. To get the best teaching we need people trained in the discipline. We have people with no science at all teaching up to Year 10.

“If want a society that can discuss climate change, the NBN etc., people have to understand the discussion and to do that they need basic training.”