Geochemical and biological research offers academics a window into earth history, enabling them to piece together events that occurred before records began. Much of our understanding of past climate change is based on geology, in particular the study of sedimentary rocks deposited in the oceans.
The paper that first recognised and defined Oceanic Anoxic Events (OAEs), written by Oxford professor Hugh Jenkyns and an American colleague, is considered a seminal contribution to geological history, that led the way to numerous studies on the effects of oxygen starvation in the oceans.
The discovery of organic-rich sediments, often described as black shales, at numerous deep-sea drilling sites during the early 1970s, led to the wider acknowledgement of the oceanic impact of climate change. At certain intervals during the Jurassic era, huge bouts of volcanic activity triggered increased concentrations of atmospheric carbon dioxide. This then caused a knock-on greenhouse effect, raising the sea-surface temperature and reducing oxygen levels in large parts of the ocean.
At the same, oceans benefited from increased nutrient levels, and as a result marine algae and bacteria bloomed. As they died, these organisms were preserved in sediments that formed on the sea floor and over time changed into source rocks for oil. It is these phenomena that illustrate the causes and effects of OAEs.
New research, published in Nature Geoscience, has for the first time examined the impact of this type of sediment deposition in lakes. The study demonstrates that lake environments responded in a similar way to climate change, developing the same anoxic conditions as in the oceans.
Led by Earth Sciences post-graduate student Weimu Xu, the work offers insight into how environmental factors have affected lake formation throughout the ages. Weimu and the team studied sediments from one of the largest lakes in Earth history - double the size of England and three times the size of Lake Superior - the largest lake (in surface area) in the world today. This ancient lake formed rapidly in the Sichuan Basin, China, as a result of Toarcian (Early Jurassic) climate change, about 183 million years ago.
Weimu spoke with Science Blog about the study’s key findings and what they can tell us about climate change today.
What is the key finding that you would like people to take from this study?
The extreme effects of past climatic changes are not limited exclusively to oceans. By dating the lake sediments to the Early Jurassic (Toarcian) period, we were able to show that large lakes formed and were affected in the same way as oceans during an OAE.
As the climate warmed, the continents experienced increased rainfall, creating lake reservoirs, which essentially acted like mini-oceans. Lake organisms became more abundant, drawing-down massive amounts of carbon dioxide from the atmosphere, which was eventually deposited into sediments. Overtime, these sediments became source rocks for oil.
Lake environments represent their own unique challenges. Did you encounter any specifically?
The biggest challenge for us was establishing the age of the sediments found in the Sichaun Basin, and proving that they were of similar age to those that formed in the oceans during the Toarcian OAE. The wealth of organic matter found in marine environments makes it quite easy to date an event, by basing it on a fossil’s geological age. But lakes do not have such fossils, which makes it much harder to determine the age of the sediments found.
A study of this nature involves a massive amount of work. How did you manage such an extensive undertaking?
Fortunately I worked with a great team. This work was led by myself, co-designed by M. Ruhl, H.C. Jenkyns and S.P. Hesselbo and involved a total of 11 people. The project is a great example of collaborative research.
We used three distinct methodologies, which would be impossible for any one researcher to master. Colleagues from the University of Durham applied radio-isotopic dating to establish the age of the sediments and colleagues from the British Geological Survey studied the pollen, spores and algae preserved in the sediments. Finally, to give us even more detail to support the age of the sediments, together with colleagues from the University of Bristol and at Shell Global Solutions International B.V., we applied stable carbon-isotope to analyse the sediments, plant and algae remains. These varied techniques convincingly showed that the sediments found, had formed at the same time as the Toarcian OAE.
We were fortunate to be able to partner with experts in these three fields, and of course our industrial partner Shell.
How long did the research take to conduct?
The study lasted from the first sampling trip in November 2013 to completion of this manuscript in September 2016. We also had to factor in time to get permission to publish the findings, from the oil companies providing the data.
Are there any long-term impacts associated with your findings?
There are definite links between the climatic event identified in the Toarcian and present-day global warming. A better understanding of past climate systems could help predict environmental and ecological changes in a future greenhouse world. While the lake we studied existed in the Early Jurassic period, there are lakes today in African and British Columbia for example, that have been affected by global warming. They are becoming more and more anoxic and some are losing fishery stocks as a result. People fixate on warmth, but anoxia goes hand in hand with warmth.
There’s a certain irony in the fact that the conditions which created oil and gas deposits millions of years ago are being recreated much more rapidly by burning of these fossil fuels.
How would you like to see this work used in the future?
Our study directly links lake formation and sediment deposition to the Toarcian OAE. By studying other lake sediments that were around at that time, researchers could establish if they also link to this event. For a better understanding of major climatic change in other intervals of the Earth’s history, people can also look and see if there were other major lake reservoirs that acted similarly.
It would also be useful to understand the impact, not only of carbon deposition, but carbon burial, during times of major climatic change, and how that impacted coal formation. This is something I am very keen to focus on next.
The paper, Carbon sequestration in an expanded lake system during the Toarcian oceanic anoxic event, can be viewed here.
Stargazing Oxford, the annual, calendar highlight for would-be astronomers of all ages, returns on Saturday 28 January 2017.
Featuring helpful tips on how to star-gaze at home, bite-sized flash talks covering the latest in astronomy and astrophysics research and the chance to take in the delights of the night sky with a range of telescopes, the event is a science lover’s dream.
Last year more than 1,200 people turned out to take in the wonders of the universe and learn first-hand, from the University of Oxford’s leading astronomers.
Workshops run by the University’s physics department and local experts from Oxfordshire’s amateur astronomy groups will take place throughout the day, and will answer questions that range from; ‘what constellations can you see in the night sky this month?’ to ‘why do stars explode’ and ‘is there life on other planets?’
Younger budding astronomers can participate in gravity defying experiments and road test their presenting skills, by hosting a space weather broadcast. The more leisurely inclined can take a tour of the night sky in an inflatable planetarium, or learn the art of AstroCrafts (age 6+).
Mark Richardson, a postdoctoral researcher in astrophysics at Oxford University, said: ‘It’s a free, fun packed day out for all the family, with a great purpose. Astronomy is a great gateway to science, for people of all ages. Children are naturally inquisitive and interested in the unknown, particularly understanding space and the world above them. It’s important to keep feeding this curiosity, otherwise our next, great astronomer may not choose a career in science.’
Stargazing Oxford will take place on Saturday 28 January 2017 at Denys Wilkinson Building, Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH. Doors open at 2:00pm and close at 10:00pm (last entry is 9:30pm).
Booking: This is a drop-in festival style event. No booking is required but we ask groups of 10+ to contact us in advance. Talks, workshops and the planetarium will be taking place every hour. Observing will take place after dark only.
*As in previous years, the number of guests we can accommodate in the building at any given time is limited, so you may have to queue outside on our covered walkway. You won’t be bored as there will be plenty of scientists outside too, entertaining you while you wait.*
Disabled visitors: There is limited access for disabled visitors. Please contact us.
Refreshments: Light refreshments will be available to buy from the canteen.
Parking: There is no parking available on site. There may be some pay and display parking on Keble Road and Norham Gardens, but we recommend you use Oxford Park and Ride if you are travelling from outside Oxford.
A conservation DPhil student at Oxford University has won the student section of the 2016 British Ecological Society Photographic Competition.
Leejiah Dorward's winning picture, You are old, Father William, features a reflectively spotty Gynanisa minettii caterpillar emerging from a thorny bush in Tanzania.
Leejiah is a DPhil student in Oxford's Department of Zoology conducting research into human-wildlife conflict in Tanzania. His research tries to understand some of the factors that contribute to conflict between large carnivores and pastoralists – for instance, understanding in which seasons and habitat types livestock are most at risk of being attacked by lions or hyenas.
He said: 'This picture was taken at my field site around Ruaha National Park in Tanzania. I frequently search for animals around my camp at night, as there are a number of slightly more unusual creatures that are more active and visible at night. This moth caterpillar's almost reflective skin was hard to miss under torchlight, and it obliged me with some interesting poses while I photographed it.
'I enjoy using photography to share aspects of the natural world that I find beautiful or unusual, so it's great to have a picture recognised by the British Ecological Society. Hopefully, along with the other photographs, my photography will help in some small way by inspiring interest in the natural world and action to help conserve it.'
Since late 2015, an epidemic of yellow fever in the central African countries of Angola and the Democratic Republic of Congo (DR Congo) has affected more than 7,000 people, causing almost 400 deaths.
An international team of researchers led by epidemiologists at Oxford University and Institut Pasteur has sought to better understand the spread of this outbreak, with the aim of making more efficient use of the limited vaccine stocks available.
'Yellow fever is a haemorrhagic fever transmitted between humans by the Aedes aegypti mosquito, and for a long time it was one of the most feared lethal diseases. In about 15-25% of people infected, it causes severe symptoms that can lead to death. Fortunately, there is a single dose vaccine to protect people for the rest of their lives.
'We analysed datasets describing the epidemic during a large urban yellow fever outbreak in Angola and DR Congo in combination with mosquito-ecological and demographic information. Our aim was to predict the invasion of yellow fever in the region during this outbreak and test whether we could predict where it would arrive next. This was done in light of a shortage in vaccine stock that became apparent during this outbreak in central Africa.
'Early invasion was positively correlated with high population density. The further away locations were from Luanda, the capital of Angola, the later the date of invasion. A model that captured human mobility and vector suitability successfully discriminated districts with high risk of invasion from others at lower risk. If, at the start of the epidemic, sufficient vaccines had been available to target 50 out of 313 districts in the area, our model would have correctly identified 27 (84%) of the 32 districts that were eventually affected. We found that by using a simple statistical model, we could identify locations at highest risk of yellow fever cases.
'From our analysis, we anticipate that the spread of the virus was the result of two factors. One of these was the increased travel between districts – especially large urban centres such as Luanda and Kinshasa, the capital cities of Angola and DR Congo respectively. Such big urban centres are hubs for mosquito activity, and the density of living contributes to the high risk of being infected. In addition, the low levels of vaccination against the virus may have contributed to the successful arrival of the virus in new regions where it had been absent previously.
'The research and model applied here is applicable for a range of diseases, including those rapidly expanding, such as Zika or Ebola. Predicting where the next location may be is important for public health policy makers to decide where to target their resources.
'The continental expansion of Zika in the Americas has shown how quickly new viruses can expand, especially in locations where they have been absent previously. Zika, for example, is also transmitted through the Aedes aegypti mosquito, the same insect that transmits yellow fever. However, in our research we point towards the importance of human demography as a main driver of spread and highlight the possibility that this research could be readily implemented in the context of other vector-borne diseases.'
A new role has been discovered for a well-known piece of cellular machinery, which could revolutionise the way we understand how tissue is constructed and remodelled within the body.
Lysosomes are small, enzyme-filled sacks found within cells, which break down old cell components and unwanted molecules.
Their potent mixture of destructive enzymes also makes them important in protecting cells against pathogens such as viruses by degrading cell intruders.
However, new research from the University of Oxford has revealed that in addition to breaking down cellular components, lysosomes are also important in building cellular structures.
‘We’ve traditionally viewed lysosomes as the cell ‘dustbin', because everything that goes into them gets chewed up by enzymes,’ said Professor Nigel Emptage from the University’s Department of Pharmacology, who led the research. ‘However, our research has revealed that lysosomes actually play a far more elaborate role, being involved in building as well as demolition, and playing a key part in structural remodelling of cells.'
The discovery was made while the team was looking at hippocampal pyramidal neurones – specialist brain cells important in spatial navigation and memory, which degenerate in Alzheimer's disease. The researchers observed that lysosomes were involved in supporting the growth of spines from dendrites, structures that increase the cell’s ability to store and process large amounts of information.
He added: ‘This discovery fundamentally changes how we view this well-known organelle, as it appears that without them new memory could not be stored in the brain. There has been a growing body of evidence for some time that lysosomes have other functions in addition to their traditional role, but it appears that they are also important in cellular construction.’
The full paper, ‘Activity-Dependent Exocytosis of Lysosomes Regulates the Structural Plasticity of Dendritic Spines’ can be read in the journal Neuron.
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