This project is investigating how the phosphorus content and phosphate oxygen isotope (Ξ΄¹⁸O-PO₄) signatures in sediment cores change over time, to establish the value of this proxy for environmental reconstruction research.β€―The research builds on a fellowship project between BGS and Loughborough University with Dr Savannah Worne, and is part of an ENVISION DTP PhD project at Lancaster University. 

The importance of phosphate oxygen isotopes

Normally, the bonds between phosphorus and oxygen in phosphate (PO₄^3-) are very stable and don’t break down easily under typical conditions on Earth. This means that oxygen isotopes within PO₄^3- remain unchanged, unless biological processes are involved. However, certain enzyme-driven reactions, both inside and outside cells, can break these bonds and allow oxygen isotopes to exchange with the surrounding water. This has led to the discovery of a temperature-dependent balance between water and PO₄^3- cycling, which can help scientists better understand how PO₄^3- is processed by living organisms.

Recent advances in analysing Ξ΄¹⁸O-PO₄ have made it easier to use them as indicators of biological cycling of inorganic PO₄^3-. Using modern water oxygen isotope (Ξ΄¹⁸O-H₂O) data, we can calculate the temperature-dependent equilibrium value for Ξ΄¹⁸O-PO₄, which reflects the complete biological turnover of phosphate.β€―β€― 

Applying this method to lake sediments is a new and innovative technique that builds on current soil methodologies and allows for past studies of phosphorus cycling. We expect that the Ξ΄¹⁸O-PO₄ value in the sediments will reflect the level of biological processing at the time of deposition, with values moving closer to equilibrium when PO₄^3- is utilised more. To date, there have only been rare applications of Ξ΄¹⁸O-PO₄ to lake sediments, with no prior applications to a lake sediment core. In part, this reflects the unknown preservation of the Ξ΄¹⁸O-PO₄ signature within the core over time.

Rutland Water

Rutland Water is one of the largest artificial reservoirs in Europe, located in the East Midlands. Spanning approximately 4200 acres, it was constructed in the 1970s to ensure a reliable water supply for the surrounding region. Over the years, the reservoir has evolved into a vital site for drinking water supply, wildlife conservation and recreational activities, drawing nature enthusiasts and visitors alike.  

A key part of the site is the Rutland Water Nature Reserve, which is composed of woods, grassland and meadows as well as eight shallow water lagoons, covering around 1000 hectares. Managed by Anglian Water and the Leicestershire and Rutland Wildlife Trust, this area of Rutland is internationally renowned for its rich biodiversity, with wetlands, woodlands and open waters providing habitats for a variety of wildlife species, including the famous ospreys. Our research aligns directly with the water quality management goals of the site, to ensure the ongoing sustainability of this unique environment.

Sampling and research activities

In collaboration with the Leicestershire and Rutland Wildlife Trust, we collected three sediment cores from a nutrient-rich lagoon in the Rutland Water Nature Reserve to study how phosphorus levels and the PO₄^3- oxygen values in lake sediments change over time.

The first core was cut into thin layers and analysed immediately to give us a baseline of current conditions. The other two cores were stored under different conditions for six months to see how much the phosphorus concentrations and isotope values might change over time. One core was sliced into layers before storage (exposing it to air), while the other was kept intact in its tube, mimicking in-lake preservation conditions. These two cores were treated with isotopically enriched water before storage, with the intention that the isotope label would appear in future data sets if biological activity persisted, even at depth. 

Preliminary discoveries

So far, the analysis of the first core has provided useful baseline results, by identifying four different pools that phosphorus is bound to: bioavailable, microbial, metal-bound and non-labile. The results hint at the varying stability of these phosphorus forms within the sediments.  This analysis also gives us an opportunity to improve our analytical methods.

Findings from the stored cores will be key to our understanding of how phosphorus in sediments behaves and changes over time, offering insights into nutrient cycling at Rutland Water. All of this data will be part of my ongoing PhD thesis.

About the author

Christopher Bengt is a PhD student enrolled at Lancaster University. His PhD is funded through the Envision Doctoral Training Partnership and the BGS University Funding Initiative.

In May 2022, I had a training placement as a PhD student in the Stable Isotope Facility of the 51ΑΤΖζ in Keyworth, Nottingham. Since stable isotope laboratories are limited in my country (Croatia), I had applied for a scholarship from the British Scholarship Trust aimed at PhD students who want to gain research experience in the UK. The training focused on the stable isotope analysis of lake carbonates and ostracod microfossils from karst lakes in Dalmatia (Croatia) to reconstruct palaeoenvironmental and palaeoclimate changes during the Holocene.

Lakes are water bodies sensitive to environmental change governed by climate and human influences. These changes are often well-preserved in lake sediments, which we can drill into to retrieve the lake sediment cores (think of a tube going through a layered cake). The cores, which record time from the youngest sediments at the top, are usually analyzed for lots of different components including their chemistry, sedimentolgy, and micropalaeontology. In these Croatian lakes the stable isotope analysis, which I undertook at BGS, and the microfossil assemblages are particularly useful and will tell us about both past temperatures and rainfall.

The training I undertook included sample preparation of small ostracod shells and other lake carbonate samples. I learnt how to analyse these materials for carbon and oxygen isotopes by isotope ratio mass spectrometry. Preparation of ostracod shells is challenging since their shells are extremely small and can easily break during the cleaning process, resulting in a loss of material for analysis. I also got experience of methods to remove subborn organic materials using a plasma ashing method, whereby a plasma source and oxygen oxidise organic materials on the surface of the shells. The plasma ashing results in nice, clean, and ready to go material for analysis using mass spectrometry.

Lake sediments are comprised of many different forms of carbonate. I wanted to analyse material that precipitated in the lake (the endogenic component) so I had to remove all other material. This was done by sieving (shells, sand etc) and bleaching (organics). To ensure that the samples are mostly endogenic I was able to get experience of the scanning electron microscope, where I could check the composition of the smallest of fragments prior to analysis.

Besides the sample preparation, I had a chance to see how large laboratories, like the Stable Isotope Facility, operate. The isotope laboratories have eleven gas-source isotope ratio mass spectrometers that are supported by a whole array of preparation laboratories. They are one of the bigger isotope facilities in the UK.

Overall, I can say that my visit to BGS was very positive and productive and I took most of my data home with me! I had the opportunity to work with experienced scientists including Jack Lacey, Kotryna Savickaite, Harvey Pickard, and Chloe Walker-Trivett: I thank them for their kindness and support during my stay. Special thanks to Prof Melanie Leng for hosting me as a PhD student and for our many talks regarding data interpretation. I would also like to thank my PhD supervisor Nikolina Ilijanić and Croatian Geological Survey for the opportunity to visit the BGS, for providing the lake sediment samples and for financial support to carry out the analysis.

I can only encourage other students from the UK and other countries to apply for scholarships at BGS, especially students with limited access to sophisticated laboratories like myself. The experience and knowledge gained at the BGS improved my understanding of stable isotope analysis and palaeolimnology, which will significantly contribute to my PhD thesis.

About the author

Ivona Ivkić Filipović is currently a PhD student at the Croatan Geological Survey in Zagreb, researching in environmental change records from Croatian lakes.

As an MRes student at Lancaster University, my dissertation is looking at the phosphorus cycle within caves, especially using the oxygen isotope signature of phosphate (PO₄) to understand phosphorus cycling and its use as a palaeotemperature proxy.

Water in caves

Water that enters caves has travelled from the ocean, evaporated and precipitated as rain, moved through rivers and soils before percolating into the cave environment. Along the way, this water picks up dissolved nutrients including carbon (C), phosphorus (P) and nitrogen (N). These offer a wealth of scientific information. Under certain conditions, cave drip waters form calcite features such as stalagmites, much like those found in Poole Cavern in Buxton, Derbyshire. Similar to tree rings and ice cores, stalagmites incorporate a wealth of environmental information as they grow, building a ‘nutrient record’ layer by layer over time.

Why study phosphate?

Phosphate (PO₄) is a key component for microbiological function, including the formation of DNA. A metabolic process exists in many bacteria (pyrophosphatase hydrolysis) that swaps out oxygen within the PO₄ molecule with oxygen from cave drip waters. This process is controlled by the temperature at which the reaction occurs. This means that we can potentially back-calculate the formation temperature using the PO₄ oxygen isotope signature.

PO₄ is naturally found in some stalagmites and, because these stalagmites take many years to grow, they could hold a record of temperature locked up in their PO₄ that is tens of thousands of years old. However, this is all currently theory: we are still unsure exactly where the oxygen within PO₄ is exchanged or how and, whilst we believe this should take place near to or within the cave, this novel approach needs testing. These are the questions on which my research will focus.

The research method

Water is being collected from stalagmite drip sites and dosed with PO₄ within Poole’s Cavern. It is hoped that natural bacteria in the water will metabolise this PO₄, β€˜locking in’ the oxygen isotope signature as a factor of temperature. The water will then be dripped onto glass plates to precipitate calcite (mimicking natural cave stalagmite formation), analysed for stable isotope composition at BGS and compared to cave temperature. By conducting the experiment at different temperatures, it is thought that an equation can be formulated that maps temperature versus PO₄ oxygen. If successful, a trend could be tracked through each layer that makes up the stalagmite, producing a temperature record though time without direct measurement.

Personally, I hope this experience will add significantly to the field of palaeoclimate research in caves and put me in better stead for a PhD studentship within the cave science field. 

About the author

Alistair Morgan is a masters by research (MRes) student at Lancaster University. His research is focused on understanding how phosphorous enters cave systems and if, as it is incorporated into stalagmites, it could be used to unravel past temperatures.

During November and December 2020, a deep borehole was drilled just off the A49, around a kilometre north of the village of Prees, south of Whitchurch in north Shropshire. The JET project science team behind this project, of which I am a member, needed to obtain a continuous core of Early Jurassic rocks in order to decipher the chronology and environments of the early part of the Jurassic Period between around 201 and around 174 million years ago.

The Early Jurassic was a fascinating epoch in the history of our planet. It was a greenhouse interval with no permanent polar ice, characterised by some major changes in the global carbon cycle. We believe that these events were mainly driven by greenhouse gases emitted by large pulses of volcanic activity.

These intervals of global warming caused substantial climatic and environmental shifts. The most dramatic of these led to a marked increase in surface water fertility and blooms in plankton populations making widespread areas of the ocean floors devoid of oxygen around 183 million years ago.

It is really important to understand all aspects of these climatic perturbations in the geological record, not least the timing of them. We are currently of course experiencing a changing climate and it is imperative that we know the timings of the onset, overall duration and recovery of fluctuating environments on our planet based on past events. It is hoped that this will help us understand what may be happening right now. We aim to help to do this by working out the astrochronology of the Early Jurassic rock record. To do this we will attempt to decipher three different cycles of sedimentation which were controlled by regular rhythms of the Earth orbit around the Sun. If we can work these cycles out effectively, using techniques such as detailed geochemistry and geophysical logging, we can use the number of cycles to determine how long it took to deposit the rock succession being studied, as well as the durations of the environmental shifts. We will also work on the environments based on aspects such as fossils and sedimentology.

The geological picture

In the UK we are fortunate to have some fantastically complete and well-preserved successions of Early Jurassic sedimentary rocks and therefore we can study Early Jurassic environments in great detail. So, a number of interested researchers put together a proposal and applied for grants from the Natural Environment Research Council (NERC) and the International Continental Scientific Drilling Program (ICDP) based on a new borehole at Prees and an existing borehole drilled by BGS at Mochras in west Wales in the late 1960s. NERC and ICDP accepted our proposals and we began to plan for the Prees Borehole in the spring and summer of 2018. The science team came up with a project name of Early Jurassic Earth System and Timescale, abbreviated to JET. This latter acronym pays homage to the famous black gemstone from Whitby that is found in Early Jurassic rocks.

scientists turned up an example of Teichichnus in the core for #FossilFriday! Prees coring is progressing well and we look forward to more Photo credit: Jim Riding

β€” JET Project (@JET_Prees)

Planning the drilling operation

We knew from legacy BGS geological mapping and two old boreholes in the vicinity that there is a really good Lower Jurassic record around Prees, so the search was on for a good site. It had to be accessible in terms of getting the borehole infrastructure set up easily, and be as far away from houses as possible because boreholes can be quite noisy! A site was found: a small corner of a farmer field, close to a main road. The science team also had to find a drilling contractor so a tendering process was instigated. As you can imagine, processes such as landowner negotiations, planning permission, tendering, etc. are relatively far from the normal day-to-day activities of a geologist working life!

The drilling operation

When all this was complete, we could finally start the drilling operation at Prees. There were a few relatively minor delays, and the pandemic did not make things easier, but we finally began to drill in early November 2020. The drilling rig was a relatively large one and it used core barrels six metres in length. A continuous core was drilled using a rotating drill string and the core barrel was brought to the surface using a steel cable when it was full, which normally took around six hours.

Teams of two geologists worked 12-hour shifts round the clock and seven days a week throughout the two month drilling operation. The geologists curated the core, which meant cleaning it, describing it, labelling the depths, way-up etc. and carefully placing it in one-metre core boxes for transporting back to the BGS core store at Keyworth. We halted drilling on 29 December 2020 and the borehole was terminated at 656 m. The β€˜terminal depth’ was in the Late Triassic, which meant that our objectives of drilling through the Early Jurassic had been fulfilled.

The first test shallow geotechnical Jurassic aged core from Prees!

β€” Prof Melanie Leng (@MelJLeng)

The JET project science team will now begin to study the Prees Borehole in detail. We will be putting the one-metre core sections through a core scanner to analyse the overall geochemistry. Samples will also be analysed for carbon isotopes to reconstruct changes in the carbon cycle throughout the Early Jurassic. Other highlights include examining clay minerals, magnetic field reversals, sedimentary structures and detailed studies on the fossils in the core especially ammonites, microfossils and trace fossils.

The JET project is primarily funded through a NERC Large Grant led by Prof Steve Hesselbo of University of Exeter.

51ΑΤΖζ is pleased to be part of a joint expedition of the International Ocean Discovery Program (IODP), focused on the Arctic Ocean – a key location in global climate change.

Despite its global importance, the Arctic Ocean is the last major region on Earth where the long-term climate history remains poorly known.

IODP Expedition 377 Arctic Ocean Paleoceanography – or ArcOP – will represent a step-change in reconstructing the detailed history of climate change in the central Arctic Ocean over the last 50 million years.

A joint expedition, it will involve expertise from the European Consortium for Ocean Research Drilling (ECORD), the Swedish Polar Research Secretariat (SPRS) and Arctic Marine Solutions (AMS) and is planned to take place in August and September 2022.

Science behind the ArcOrp Expedition

The Arctic Ocean is a very sensitive and important region for global climate change, and is unique in comparison to the other oceans on Earth. Due to complex feedback processes (collectively known as β€œArctic amplification”), the Arctic is both a contributor to climate change and a region that is most affected by global warming.

Major advances in understanding were achieved in 2004 when the successful completion of IODP Expedition 302: Arctic Coring Expedition – ACEX, also implemented by ECORD, marked the start of a new era in Arctic climate exploration.

The ArcOP expedition will explore a critical time interval, spanning the period when prominent changes in global climate took place during the transition from the early Cenozoic Greenhouse world to the late Cenozoic Icehouse world.

An international team of scientists will collect about 900 m of sediment cores at two sites along the Lomonosov Ridge.

We anticipate that the sedimentary record that the Arc-OP expedition is targeting will provide critical puzzle pieces enabling the scientific community to better understand the drivers, feedbacks, consequences, and varying rates of Cenozoic climate change at both regional and global scales.

Prof Kristen St John, ArcOP Co-chief Scientist.

A unique and challenging expedition, a fleet composed of a scientific drillship supported by two icebreakers will be used to make drilling possible in this permanently ice-covered region.

Such a multi-vessel approach was employed by ECORD for the first time during the ACEX Expedition in 2004.

The expedition will last for about seven weeks offshore and will be followed by intensive investigation and sampling of the cores onshore to unlock their climate secrets.

51ΑΤΖζ will help to lead the implementation of the expedition through its role as the co-ordinator of the ECORD Science Operator (ESO), in close collaboration with SPRS and AMS.  

51ΑΤΖζ staff are excited to be part of this ambitious IODP expedition that will see us manage, co-ordinate and support an international team of scientists through our role as the coordinator of the ECORD Science Operator.

Our role is very much to support the team efforts to uncover and understand the history of climate change in the central Arctic Ocean over the last 50 million years.

We will provide expedition management and coring oversight, and work with our partners to provide facilities and services for the curation, databasing, archiving and analysis of collected cores and samples, and downhole logging services.

David McInroy, BGS Geoscientist.

Further details of the expedition can be found on the .

More information

An international research team led by the Justus Liebig University Giessen and the University of Cologne, in collaboration with BGS, gained these new insights into evolution by drilling deep into the sediments of Lake Ohrid.

The 1.4-million-year-old lake on the border between Albania and North Macedonia is not only the oldest lake in Europe, but with more than 300 endemic species, i.e. species that only occur there, it is also the most species rich.

To study the evolutionary dynamics of Lake Ohrid since its formation, the scientists combined the environmental and climate data of a 568-meter-long sediment core with the fossil records of over 150 endemic diatom species.

Dr Jack Lacey, a geochemist from BGS, used chemical data from the mud to understand past changes in the hydroclimate of Lake Ohrid.

The combination of our data and the fossil diatom record of Lake Ohrid provide us with a link between geological processes, environmental change, and the biological evolution of endemic species within the lake.

Using geochemical data from the layers of mud that built up over time at the bottom of Lake Ohrid, we have unravelled a 1.4-million-year history of lake development and climate change, that are interwoven and captured in the sediment record.

Dr Jack Lacey, BGS Geochemist.

The data show that shortly after the formation of the lake, new species emerged within a few thousand years. Many of them died out again very quickly in the relatively small and shallow lake.

The research team explains this by the fact that young lakes of small size offer many new ecological opportunities, but are also particularly sensitive to environmental changes such as fluctuations in temperature, lake level, and nutrient availability.

The geochemistry of lake muds is a recorder of past changes in rainfall and major shifts in the water level of Lake Ohrid.

After the lake became deeper and larger, as indicated by shifts in the geochemistry, the speciation and extinction processes slowed down dramatically.

The scientists attribute this to fewer new habitats emerging, the species richness approaching an ecological carrying capacity, and an increasing environmental and climate buffering of the lake.

The finding that, in the history of Lake Ohrid, a volatile assemblage of evolutionarily short-lived species developed into a stable community of long-lived species provides a new understanding of the evolutionary dynamics in ecosystems.

The study, which has now been published in the journal Science Advances, has importance for future biodiversity research.

Citation

Wilke, T, et al. 2020. . Science Advances, Vol. 6(40), eabb2943. DOI: https://doi.org/10.1126/sciadv.abb2943

About the author

Mud taken from deep within Europe oldest lake is helping scientists understand how Mediterranean rainfall has varied over the past 1.4 million years and how it could change in the future.

While scientists have been able to predict Europe long-term future temperature increases, the picture of winter rainfall has been less certain due to a lack of data.

Winter rainfall is important for the region as it offsets summer drought and controls the amount of water available to meet agricultural, domestic, and industrial demand.

Now, a 570 m column of mud from Lake Ohrid in North Macedonia is giving scientists access to 1.4 million years of Mediterranean rainfall data, as reported in Nature today.

The mud was extracted from Lake Ohrid during an International Continental Scientific Drilling Program (ICDP) project, which involved scientists from around the world.

Dr Jack Lacey, a geochemist from BGS, has used chemical data from the mud to understand past changes in rainfall.

The sediment from Lake Ohrid has allowed us to unravel an extended climate history for the Mediterranean region in exquisite detail. Until now we could rarely go back beyond around 10Μύ000 years.

At BGS we investigated the chemistry of the mud that built up at the bottom of the lake, measuring the oxygen and carbon chemistry of minerals, which is mainly controlled by how wet the climate was. The consecutive layers tell us about the evolution of climate over time.

Dr Jack Lacey, BGS Geochemist.

Overall the mud shows recurring periods of higher rainfall that tended to occur during hotter periods when the Earth suffered higher atmospheric levels of CO2. These periods were also marked by less polar ice, and large seasonal differences in the amount of sunlight reaching Earth surface.

We found a strong connection between Mediterranean winter rainfall and African summer monsoon strength throughout our record.

This means that not only is solar energy a key driver of the African monsoon, but also has a dominant control on rainfall variability in the Mediterranean over the last 1.4Μύmillion years.

Dr Jack Lacey, BGS Geochemist.

The link between rainfall in the Mediterranean and the African monsoon shows that the Lake Ohrid data can be β€˜scaled-up’ to describe global climate processes.

Any change in the amount of winter rainfall in the Mediterranean will impact water availability and could have strong social and economic implications for this densely populated region.

The key processes controlling rainfall extremes in the Mediterranean we found from this research are similar to the conditions predicted to develop in the future due to human-made climate change.

The next step is to use this exceptional record from Lake Ohrid to link geology and biology to see how climate and environmental change may have caused the evolution of plants and animals in the lake.

Prof Melanie Leng, BGS Chief Scientist for Environmental Change Adaptation and Resilience.

51ΑΤΖζ worked with scientists from around Europe on the research. .