Our Changing World
Thursday 21 May 2015, with Alison Ballance, Ruth Beran & Veronika Meduna
On This Programme
- ExStream - How River Life Responds to Environmental Stresses
- Don't Just Sit There - Do Something
- DNA Trafficking Between Cells
- We Are What We Eat - What Hair Can Tell Us
- Megathrust Earthquakes Below Central New Zealand
- Top 10 New Species for 2015
ExStream - How River Life Responds to Environmental Stresses
By Alison Ballance
"What we see causing the greatest harm to aquatic invertebrate communities in these streams is deposited fine sediment."
Jeremy ‘Jay’ Piggott, University of Otago freshwater scientist
An ambitious experimental set-up is allowing freshwater scientists to tease apart the impact that environmental stresses, such as increased sediment and nutrient run-off from intensive farming, are having on the declining health of streams and rivers.
“We’re interested in how multiple stresses affect freshwater biodiversity," says Jeremy 'Jay' Piggott. "So when we think about agriculture, which is one of the major drivers of change in New Zealand freshwaters, we think about nutrient enrichment from run-off, we think about sedimentation coming in and smothering the [stream] bed. We can also think about herbicides, pesticides, and we can think about deforestation upstream which changes the riparian cover which in turn changes the water temperature. We can also think about changes in water quantity, with water abstraction for irrigation.”
Jay says that all of these stresses are happening simultaneously, so it’s often difficult to work out which is causing the effects or harm that’s being observed.
“These studies we’re conducting – which are quite pioneering – are trying to disentangle all those effects.”
What their results have shown so far is that deposited fine sediment is a key stressor in streams and rivers, as it smothers habitat. Invertebrates tend to respond by drifting downstream away from the affected area. The researchers have observed a complex interplay between the effects of sediment, increased temperatures and increased nutrients.
"Fine sediment tends to be really bad on its own – but other stresses tend to make its effects worse.”
The most effective mitigation is to plant riparian vegetation along the stream banks, as this shades the water and prevents nutrient and sediment run-off. Jay says it is particularly important to plant riparian strips along small streams that feed into larger rivers.
The ExStream, or Experimental Stream Mesocosm System, comprises 128 miniature circular streams. It has a 20 metre long, 5 metre high and 5 metre wide scaffold structure, and about 10,000 individual pieces of piping and other bits of plumbing paraphernalia that connect to a pump submerged in the nearby Kauru River, a relatively pristine river running through farmland in North Otago. Jay developed the system during his PhD studies, and laughingly says that “on successful completion of my PhD I informed everyone that I am now officially a plumbing and hose doctor.”
The University of Otago researcher and his team are using the system to tease out how freshwater ecosystems respond to multiple agricultural stresses such as nutrient and sediment run-off as well as climate change and rising water temperatures.
"Climate change is the big elephant in the room when we think about the impact of human activities,” says Jay. Rather than simply making matters better or worse, he “would argue that it’s just going to make things more complicated.”
As well as increasing water temperatures, climate change is predicted to being changes to precipitation patterns that might result in more frequent droughts as well as more frequent storm and flood events. Increasing carbon dioxide levels in freshwater are not well understood, but are believed to impact on the availability of food in the food web.
The system currently sits on the edge of a field, and it takes water directly from the nearby Kauru River.
The water and the aquatic life it contains are piped to the mesocosms, which are actually ring-type cake tins with a central hole that allows the water to flow through. The system is exposed to the same weather and light conditions that the river experiences, which means it is a much more realistic experimental set-up than one situated in a lab. Prior to an experiment the mesocosms are naturally colonized by periphyton and invertebrates from the river.
“The substrates in the mesocosms reflects the natural substrates that we see in rivers running through sheep and beef farms here in North Otago, and we’ve got a natural community in there that you would expect to see in a relatively pristine stream.”
The researchers can manipulate a range of experimental variables. For example they can decrease or increase the rate of water flow, add different grades and amounts of fine sediment, increase temperature by heating the incoming water using gas califonts, and drip in either nutrients such as nitrogen or phosphorus, or commonly used agricultural chemicals such as nitrogen inhibitor, and glyphosate or Roundup.
“We allow the organisms coming in here to do what they actually do in their natural environment, which is either to decide to stay or leave, or they can develop there and emerge as adult insects. So we can look at immigration, emigration and development processes [in the invertebrate populations].”
In the latest experiment the research team is experimenting with three different grades of fine sediment and four different water speeds. Master’s student Lisa Carlin will be measuring the effect on motile algae, while student Matthew Ward will be measuring the impact on the invertebrate community.
The ExStream system is also being used in Germany. Jay and colleague Christoph Matthaei have created a company to market the system and they are hopeful it will soon be in use in other countries such as Japan.
Don't Just Sit There - Do Something
By Alison Ballance
I find it quite amazing that with just this little tiny bit of exercise that you do throughout the day, you get such significant results on your blood glucose.
Meredith Peddie, Department of Human Nutrition, University of Otago
Getting off your butt is better for your health – and doing it regularly and frequently is the key.
Just getting out of your chair and walking along the corridor, or up and down a flight of stairs.”
That, in a nutshell, is what the latest evidence is showing, says post-doctoral researcher Meredith Peddie, who has already shown in her PhD research that ‘if you sit for a long time you’re less able to clear sugar out of your bloodstream effectively, but if you get up and move around you’re more effective at clearing glucose.”
Now, she’s investigating in more detail what happens to our metabolism after meals when we interrupt sedentary behaviour with different amounts of exercise. In particular she’s interested in measuring “how quickly and efficiently you clear [both] fat and sugar out of your blood stream after you’ve eaten a meal. Getting up is good for clearing sugars and we’re just trying to see if it affects lipids as well.”
“Even in people who don’t have diabetes, if you have higher levels of blood glucose your risk of developing health-related complications is higher long-term.”
Meredith says that preliminary research in this area using rats had showed that sitting resulted in a decrease in the production of an enzyme called lipoprotein lipase, which is responsible for clearing triglycerides from our blood stream. While her previous work didn’t show this she suspects that it was to do with study design, and with the speed at which humans produce lipoprotein lipase after exercise compared to the rodent model.
Meredith is currently running a study at the University of Otago in which 36 participants each come into the clinic for eight days, and take part in four different exercise strategies. The four strategies are: sitting all day with no exercise; sitting all day followed by half an hour of steady exercise; sitting interspersed with brisk walking up an incline for two minutes on a treadmill every half an hour; and walking for two minutes on a treadmill every half an hour plus 30 minutes of continuous exercise at the end of the day. Participants receive the same meals each day, have their blood parameters and oxygen regularly measured, fill out appetite questionnaires and wear accelerometers so their exercise outside the clinic can be measured as well.
One of the benefits of this cross-over study design is that each person does each of the exercise interventions so their results can be compared against themselves as well as against other people.
One of the interesting spinoffs of this research is that the researchers themselves, including Meredith as well as Master’s student Stephen Fenemor, have made themselves make-shift standing desks to work at.
After spending most of your time reading about how bad sitting down is for your health, it’s hard to stay sitting."
DNA Trafficking Between Cells
By Veronika Meduna
We have been doing work with two different brain cell types, astrocytes and neurons, and have been able to show that in early development … mitochondria can track between cells. This seems to be a normal communication process between cells.
Mike Berridge, Malaghan Institute
In a world first, scientists have found that DNA can shuttle between cells in an animal.
The discovery describes a fundamentally new process that challenges textbook science and will undoubtedly open up new areas of research – but perhaps more importantly, it raises the possibility of new therapies for diseases of the heart and brain, including neuro-degenerative conditions such as Alzheimer's and Parkinson's, and possibly cancer.
Lead by cell biologist Mike Berridge at the Malaghan Institute of Medical Research in Wellington and Jiri Neuzil at Griffith University in Queensland, Australia, the team found that tumour cells that had their mitochondrial DNA removed can import replacement DNA from surrounding, healthy cells.
Cellular power generators
Most of our DNA is bundled up tightly in chromosomes in the nucleus of each cell, but there is also a much smaller amount of DNA inside cellular structures called mitochondria. These organelles act as power generators, producing the energy a cell needs for chemical reactions. This mitochondrial DNA, or mtDNA, codes for only 37 genes (as opposed to around 20,000 genes inscribed in our nuclear DNA) and is sometimes referred to as the second genome.
Mike Berridge has a long-standing interest in how cells produce their energy – driven by the fact that mitochondria are clearly the main source in healthy cells, but cancer cells rely on a different mechanism.
A key question for his team is whether removing mtDNA from cancerous cells could thwart the development of tumours. To answer that question, they developed a melanoma and breast cancer cell line with no mitochondrial DNA, which grew well in cell culture, and injected these cells into a mouse.
Mike Berridge says that if these cancer cells have functioning mtDNA, they invariably grow into aggressive tumours that metastasise and spread throughout the body within seven days.
“We were able to show that these cells without mitochondrial DNA would not grow as a tumour for quite a while, for a month. They just sat there, but then all of a sudden they started to grow, and they grew almost up to the rates of normal tumour cells.”
The team checked the tumour cells and found that they had somehow acquired mtDNA, and after more detailed tests it was clear that the DNA they now carried had come from the healthy cells surrounding the tumour.
“We found differences that showed that the mitochondrial DNA was the genotype of the mouse into which the cells had been injected,” he says.
Showing that this transfer of mtDNA was happening was one thing. The next challenge was to work out how, and it turns out that it might not be just the mtDNA that shuttles between cells, but the whole mitochondrium. And what’s more, this could be a common repair and maintenance mechanism in the body.
There’s evidence that stem cells can supply mitochondria to heart muscle cells that have damaged mitochondrial DNA. That opens up an area of whether or not hearth problems that relate to energy supply in cardiac muscle, or in fact any muscle system in the body, might invoke the mechanisms of mitochondrial transfer to repair damaged systems.
The Malaghan Institute team is even more excited about the prospect that mitochondrial transfer could play a major role in healthy brain function as well as in neuro-degenerative conditions such as Alzheimer's and Parkinson's.
“We have been doing work with two different brain cell types, astrocytes and neurons, and have been able to show that in early development, or in neonatal cultures, mitochondria can track between cells. They move along connections between cells and the astrocytes will supply the neurons with mitochondria. Now this is in situations were we’re not damaging anything. This seems to be a normal communication process between cells.
“We’re very excited about this because this might bring in a new idea that brain cell function is contributed to by mitochondrial replacement from cells that maintain the nerve cells but are not nerve cells themselves.”
Given the brain’s high need for energy, this discovery could mean a rethinking of healthy brain development.
Nerve cells in our bodies can extend from the bottom of our spine down to our big toe, half a metre or a metre. In whales one nerve cell can extend 30 metres, and then you have the dilemma of how all the energy required at the nerve ending is provided and maintained throughout the life of that neuron, which may be years.
The textbook version is that mitochondria travel along the length of the neuron, but Mike Berridge says his team’s work suggests that “this might be going on at a local level, by DNA transfer between different cell types to maintain that high energy demand of nervous cell function and brain function”.
He says that the process might even work both ways. “There’s preliminary evidence that suggests that optic nerve cells can package up damaged mitochondria and transfer them to another cell type, the astrocyte, for processing. So our idea would be that the process can occur in reverse, that astrocytes can provide healthy, young, vibrant mitochondria to maintain nerve function throughout the life of that neuron.”
The findings also raise the possibility of new therapeutic approaches to neuro-degenerative diseases such as Alzheimer's and Parkinson's.
“Do [these conditions] really have a component of a restriction of the energy supply system in the brain? If they do, can we get in there and do something about it. Can we understand the processes that go on in the brain that control that energy.”
Apart from healthy brain and heart function, mitochondria are also associated with more than 200 diseases, which involve changes in mtDNA. Mike Berridge says that understanding the processes whereby mitochondria can move between cells could help to improve the body’s repair mechanisms and to address problems relating to mitochondrial diseases.
As far as new cancer therapies are concerned, he is cautious. “Mitochondrial function is needed by tumour cells, but tumour cells don’t use their mitochondria a lot. The more mitochondrial activity, the more a cell is driven to differentiate and to function, so it won’t divide very well if it’s using its mitochondria all the time. There might be a way of manipulating the balance to drive cells to use their mitochondria and essentially differentiate.
We think that cancer cells need an optimum amount of energy. If they have too much from their mitochondria, they won’t continue as cancer cells. If they have too little or none, they can’t grow as cancers, so understanding what the tumour cell needs and how to push it outside of its comfort zone may be very important in addressing tumours. It’s about understanding the biology behind the processes … which might then lead us on to be able to control that process, and to control cancer in that away.
We Are What We Eat - What Hair Can Tell Us
By Alison Ballance
We’re trying to improve nutrition in pregnancy. Because if we can get a baby thriving in the womb, those babies thrive in childhood and in adulthood. And a key component to the optimal environment for the baby inside the womb is the mother’s diet and nutrition.
Scientist and obstetrician Philip Baker, Gravida and University of Auckland
Gravida researchers are hoping to find a pioneering new use for the hair on our heads. By identifying diet ‘biomarkers’ in hair and blood samples from 1200 pregnant Singaporean women, they hope that it will allow them to find out which women are likely to suffer pregnancy complications.
Traditionally, researchers have studied diet by getting people to keep food diaries. And while blood and urine samples give an insight into food intake over the previous day or two the University of Auckland researchers are confident that hair contains a metabolic record of what someone has eaten over the previous months.
“Hair grows about one centimetre per month,” says post-doctoral researcher Karolina Sulek, from the Liggins Institute at the University of Auckland. “And so we’ll be able to see [back to] what happened before pregnancy, then in first and second trimester etcetera.”
Karolina makes the analogy that the metabolic record of a single strand of hair is like the record kept by growth rings in trees – the information laid down in each ‘ring’ relates to the environmental conditions at the time.
The Gravida team is leading the way in using hair in metabolomics research, although they have actually had difficulty finding existing cohort studies that have collected hair.
They have just received hair samples from 1200 women who took part in the GUSTO study – Growing Up in Singapore Towards Healthy Outcomes, but have already trialled the technique.
“We’ve studied the GUSTO cohort,” says scientist obstetrician Philip Baker. “We’ve now collected and studied a cohort in China, and in both cases we can get a very accurate handle on particular pregnancy complications by studying hair.”
Pregnancy complications include maternal diabetes, pre-eclampsia and the failure of a baby to thrive, and they affect millions of babies and mothers each year. But Philip is hopeful that a personalised diet plan could help alleviate many complications.
“It’s very simplistic to think that one diet is good for everybody or one diet is bad for everybody, “ says Philip. “The real value of this project is that it is trying to get a handle on optimizing the diet and nutrition for a particular pregnant women. In the long run what we’d like to do is profile a woman, either before she gets pregnant or in the early stages of her pregnancy, look at her environment particularly her diet, and look at the way her body is responding to that – her metabolic profile. It’s trying to move to much more tailored and individualized advice
Philip says one of the real values in using hair is that the hair doesn’t need to be stored in a fridge or freezer, and it doesn’t need to be processed in any way, so it’s a technique that could be easily used in less developed countries.
Philip Baker says that the hair metabolome is an exciting area – “just how much promise it holds, if we’re being entirely candid we don’t yet know, but the first signs are very encouraging.”
Megathrust Earthquakes Below Central New Zealand
by Veronika Meduna
Subduction earthquakes have the potential to be very big because subduction zones are very big features.
GNS Science earthquake geologist Kate Clark
For the first time, geologists have found direct evidence for large “megathrust” subduction earthquakes beneath central New Zealand, along the southern part of the Hikurangi margin, which marks the collision zone between the Pacific and Australian tectonic plates.
The team identified the geological signatures of two subduction earthquakes that have ruptured in the past 1000 years, and this is the first direct evidence that the plate boundary under the Cook Strait-Marlborough area can produce large earthquakes.
Lead author and GNS Science earthquake geologist Kate Clark says subduction earthquakes differ from other quakes in that they occur at the interface between two plates, rather than along faultlines within the upper plate.
They are responsible for some of the biggest quakes – and tsunamis – in the world, including the recent magnitude 9.0 Tohoku earthquake and tsunami in Japan in March 2011 and the magnitude 9.3 Indian Ocean earthquake and tsunami in December 2004.
“Subduction earthquakes have the potential to be very big because subduction zones are very big features,” says Kate Clark. “And being able to generate a larger earthquake means that ground shaking will go on for a longer time.”
Kate Clark says geologists already had some evidence for such earthquakes on the northern section of the Hikurangi margin so the risk is not new for New Zealand, but this study provides greater certainty.
I feel like our research is just the start of what we can understand about these earthquakes. Now we know that they do occur, and we have found evidence of what they do at one location. What we will now do is try to look for other locations around the lower North Island and upper South Island of these same earthquakes, and if we can find out … how much uplift and subsidence there was or how large the tsunami was, then we can combine all that information and hopefully one day start to understand the magnitude of the earthquake.”
The team identified the quakes from sediment cores extracted from Big Lagoon, a large coastal lake east of Blenheim. Radiocarbon dates of organic material from different levels of the cores show evidence of two sudden subsidence events, first at 880 to 800 years ago and again at 520 to 470 years ago, when the land dropped by up to half a metre.
Sudden drops like this can only be explained by moderate-to-large earthquakes, and these two events do not match any known significant earthquakes on nearby faults in the upper Australian plate.
“The findings are significant in terms of understanding earthquake and tsunami hazards in the lower North Island and upper South Island,” says Kate Clark.
Judging by the sedimentary debris found at the time of the first earthquake, this event was accompanied by tsunami that was more than three metres high and swept more than 360 meters inland.
If a similar event were to happen today, she says the damage would be significant.
“An earlier study, which modelled a magnitude 8.9 earthquake - that is our worst-case scenario - estimates in the Wellington region alone about $13 billion of damage and several thousand fatalities.
“I should point out that most of the fatalities are probably from the tsunami and not from the earthquake shaking, so if we can get the message across to the people to heed tsunami warnings and self-evacuate when they feel a strong earthquake, then these fatalities can be reduced.”
From the evidence available, the team couldn’t estimate the size of the two quakes, but Kate Clark says quakes with similar impacts in comparable geological settings are larger than magnitude 7.5.
“We would like to go further back in time and find evidence of older subduction earthquakes,” she says. “With a longer record of past subduction earthquakes we can get a better constraint on the recurrence of such earthquakes, which will help to forecast future subduction earthquakes.”
Top 10 New Species for 2015
By Alison Ballance
A cart-wheeling spider from Morocco. A Japanese pufferfish, whose mysterious underwater ‘crop circles’ puzzled scientists for nearly 20 years. And the Chinese bone-house wasp, which uses dead ants to protect its nest.
What these animals have in common is that they’ve just been recognised in the Top 10 New Species for 2015.
The global list is compiled annually by the International Institute for Species Exploration, at the State University of New York. It’s a hotly contested honour, as the Top Ten are chosen from nearly 18,000 new species described by scientists during the previous year.
And it’s not just animals on the list. Dr Pieter Pelser and Dr Julie Barcelona, from the School of Biological Sciences at the University of Canterbury, described an unusual plant from the Philippines.
“It’s a quite bizarre species,” says Dr Pelser. “It looks more like a coral colony than a plant, and because it looks so much like a coral we named it Balanophora coralliformis.”
“It’s a parasitic plant, so it taps into the roots of nearby plants to steal their water and nutrients for its own use.”
Botanists Dr Pelser and Dr Barcelona found the plant on a remote mountain on the Philippine Island of Luzon. They knew of its existence from photos that had been taken by a Filipino colleague, and they recognised that it was different from any other species of Balanophora known to science. “We had an opportunity to do field work in the area the photo was taken, and fortunately we got lucky and we found it.”
The Top 10 New Species list is released each year to mark the birthday of Carolus Linnaeus, an 18th century botanist who‘s considered the father of taxonomy. Dr Quentin Wheeler, President of the College of Environmental Science and Forestry at the State University of New York says the purpose of the list is to draw attention to the world’s remarkable biodiversity.
“The purpose of the Top Ten is to bring attention to how little we know about life on earth. In 250 years we’ve discovered fewer than two million kinds of plants and animals, and the best estimates are there another 10 million awaiting discovery. And many of those will inevitably disappear before they’ve ever been discovered and given a name.”
The peculiar parasitic plant was almost immediately declared endangered after it was discovered, as fewer than 50 plants have been found.
Not all the new species are rare. Two turned out to be hiding in broad daylight – a 23-centimetre long stick insect is common in a Vietnamese town, while Mexican villagers often use a beautiful – and new to science - bromeliad in their elaborate Christmas altar displays.
Also on the Top 10 New Species list:
A small feathered dinosaur – nick-named the ‘chicken from hell’ – and described from three fossil skeletons found in Dakota, USA.
Dendrogramma enigmatica - a mysterious marine creature from Australia that may be an entirely new phylum of animals, somehow related to jellyfish and comb jellies.
An Indonesian fanged frog that, unlike almost all other frogs, gives birth to live tadpoles.
And a beautiful Japanese sea slug that comes in shades of blue, red and gold.
Coming up on Our Changing World on Thursday 28 May 2015
The mysterious and sweet-smelling, parasitic plant Dactylanthus, a pop-up MRI, and Plant and Food’s Hop Lab.