9 minute read
ALKENoNE
Algal lipids open a window into climate records
Analysis of algal lipids in both lakes and on the sea surface can help scientists to reconstruct past temperature records, from which new insights can be drawn into the likely future evolution of the climate. We spoke to Dr Jaime L. Toney and Dr Antonio Garcia-Alix about their research into using algal lipids to extend human instrumental records further back in time
A type of lipid produced by algae, alkenones are highly responsive to water temperature, and have long been used as fossils to reconstruct past climate records. Based at the University of Glasgow in the UK, Dr Jaime L. Toney is the Principal Investigator of the ALKENoNE project, an ERC-backed initiative aiming to analyse these lipids and build more detailed climate records. “The main objective in the project is to record temperature and precipitation from a number of lakes in Canada in a quantitative way, so that we can extend human instrumental records further back in time,” she explains. The number of double bonds in alkenones varies according to the water temperature at the time the algae were growing; Dr Toney and her colleagues are analysing alkenones from over 100 lakes in Canada, which she says have some interesting features. “These lakes have salinities which range from being completely fresh to having four times the salinity of ocean water. Because they are spread across a large latitude range, they also have a large temperature gradient of about 9 degrees,” she outlines.
This variability allows researchers to calibrate the biomarkers or lipids that are found in the lakes to all these different environmental conditions, which is a key part of the project’s agenda. The main factor that complicates temperature calibration with respect to lakes is that researchers need to know the time of year at which these compounds were produced. “For instance, if the algae are producing these compounds in the Spring, then you’re going to be recording temperatures from Spring, if they’re producing them in Summer, then you’re going to be recording temperatures from Summer, and so on,” explains Dr Toney. Previously Dr Toney
BECS PhD student and Nuffield Placement summer intern splitting lake sediment cores. ©Jaime L. Toney, PI of ERC-funded ALKENoNE project.
developed a temperature calibration by collecting water samples from different depths within a single lake, now she aims to investigate whether this calibration is applicable to this larger set of lakes in Canada. “Ultimately we’d like to understand the algae that produced these alkenones in sufficient depth to come up with a single calibration that can be used regardless of location,” she says.
Information sharing
Effective collaboration and information sharing is central to this wider goal. Dr Toney and her colleagues work with a number of different groups, including scientists at the University of Regina in Saskatchewan who have gathered environmental data from hundreds of lakes in the surrounding area. “We have a really robust database that we can refer back to when we’re trying to look at changes within the lakes and what they’re recording,” she outlines. Researchers are also collaborating with the NAOSIPUK project, an initiative working to reconstruct the North Atlantic Oscillation over the Holocene period. “We’re looking at the sampling of surface sediment in lakes, to get information about the
alkenone or diol composition of these sediments,” says Dr Antonio Garcia-Alix, the project’s Principal Investigator. “This composition is mainly related to temperature changes – if we have a thorough record of temperature in these lakes, we can look to establish a proper calibration for these proxies.”
The ALKENoNE project’s research includes lab-based work, with scientists also culturing algae in the laboratory to further refine the temperature calibration. This is technically demanding work, as it’s important to isolate the algae from bacteria and other organisms. “We’ve had the most success with what are called enrichment cultures, where we essentially take mud from the bottom of a lake, and we add it to a nutrient media. As it starts to grow, we remove individual organisms or algae that we see, under the microscope, and then try and get individual cells to grow and multiply, so that we have just a pure strain of that algae,” says Dr Toney. There are less variables to consider with these laboratory-generated samples, allowing researchers to draw more direct inferences. “It ground-truths the relationships you see in the field that might be complicated by salinity, sunlight, or other factors,” explains Dr Toney. “We want to show that what we’re seeing in the lab is also what we’re seeing in the field.”
This is a challenging goal, as the alkenones are produced by multiple different species of haptophyte algae. Researchers are applying genomics techniques to investigate how many
different species of algae are producing the alkenones, and then using the labgenerated cultures to make sure that the different species have the same calibration. “We can ground-truth that with the short sediment cores that we have, that overlap the instrumental record. So we can reconstruct temperature back over the last hundred years or so, where we have human records of temperature change, and we can make sure that the proxy matches up to the instrumental record,” continues Dr Toney. “We’re also looking at other biomarkers, including diols from algae
quantitative way, so that we can extend human
instrumental records further back in time
Alkenone-producing algae from the North Great Plains. ©Bob Andersen, Emeritus Director, Provasoli-Guillard National Center for Marine Algae and Microbiota (NCMA). High-resolution sediment core from the Northern Great Plains lakes. ©Jaime L. Toney, PI of ERC-funded ALKENoNE project.
Full Project Title
Algal Lipids: the Key to Earth Now and aNcient Earth (ALKENoNE)
Project Objectives
The ALKENoNE project uses state-of-theart, interdisciplinary techniques to model the relationship between biomarkers and the environment. Measuring and modelling biomarkers from lake sediment cores will generate past temperature and hydrologic records that will assess how past extreme temperature, drought, and flood events inform future drought risk in the Canadian Prairies.
Project Funding
Funding comes from an ERC Starting Grant (2015-2020, 637776, €1.2M) to Jaime L. Toney the project ALKENoNE – Algal Lipids: the Key to Earth Now and aNcient Earth and PhD studentship through the NERC IAPETUS Doctor Training Partnership.
Project Partners
• Professor Peter Leavitt (https://www.uregina.ca/science/biology/people/ faculty-research/leavitt-peter/index.html) • Professor Yoshihiro Shiraiwa (http://plmet.biol.tsukuba.ac.jp/index-en.html, https://www.researchgate.net/profile/ Yoshihiro_Shiraiwa2) • Dr. Ian Watson (http://www.gla.ac.uk/schools/engineering/ staff/ianwatson/#/researchinterests)
Contact Details
Project Coordinator, Dr Jaime L Toney Senior Lecturer (Associate Professor) in Organic Geochemistry University of Glasgow Geographical & Earth Sciences G12 8QQ T: +44 (0)141 330 6864 E: jaime.toney@glasgow.ac.uk W: http://environmentalbiomarkers.co.uk W: http://www.gla.ac.uk/schools/ges/ staff/jaimetoney/
Dr Jaime L Toney
Dr Jaime L. Toney is the leader of the research group Biomarkers for Environmental and Climate Science (BECS) at the University of Glasgow, UK that develops and applies the study of organic molecular fossils called biomarkers to understand past and present environmental and climate change. Fluorescence genomic techniques allow for visualization of alkenoneproducing algae (green) and autofluorescing diatom algae (red). ©Jaime L. Toney, PI of ERC-funded ALKENoNE project.
and tetraethers from bacteria - we know from previous studies that those are related to temperature and pH. If we have all of these different biomarkers and can look at them in the same sample, then we can then start questioning whether there’s something else that influences the biomarker. So it’s really a robust test.”
Bacterial proxies
The group plans to spend some time over the next few months collecting sediment cores from a number of lakes in Canada. The initial goal is to reconstruct records of the last 2,000 years and look at how they overlap with instrumental records, aiming to validate the proxies, before looking further back. “We want to go back further
in time and look at changes that have occurred over longer time periods,” says Dr Toney. Most of these lakes formed when the landscape was covered by an ice-sheet, and the landscape has only been exposed for between 8,000 and 12,000 years, so there are a lot of data. “Based on other sites that we’ve cored in the region, we expect that we will be able to get up to 15 metres worth of sediment, covering the past 12,000 years or so,” stresses Dr Toney. “After our field season we’ll bring the sediment cores back to Glasgow. We’ll start out by radiocarbon-dating them to understand how old they are, then we’ll start collecting samples from the cores and reconstructing the past climate.”
This includes both reconstructing the longer record, looking as far back as the last 12,000 years, and also over much shorter timescales, around the last 2,000 years. Detailed records of changes over this period could eventually enable researchers to more precisely investigate the impact of human activity on the climate. “By reconstructing the climate over the past 2,000 years in very high resolution, we can see how trends have changed during the Anthropocene period,” outlines Dr Toney. Understanding how the climate changed in the past could also help scientists understand how it is likely to evolve in future, which is another aspect of the project’s research. “We aim to understand how the climate is changing in this particularly region, in terms of not only temperature variations, but also in assessing future drought risk,” says Dr Toney.
The project’s findings could be used to inform the development of climate models designed to forecast future changes. While local data is an important element in climate modelling, Dr Toney says it’s important to also consider the wider picture, and the influence of other climate events. “For instance, El Niňo is an event that occurs in the tropical Pacific Ocean, but it is strongly correlated with certain events that happen in Canada, and even here in Europe,” she points out. In the immediate term, Dr Toney and her team of colleagues are continuing their genomics and sedimentary analysis work, after which they will look to publicise their findings more widely. “We’ll publish a number of papers describing how these different biomarkers are related to the environmental parameters, and which ones could potentially work as proxies,” she says.
