Recent research into the chemistry of ancient pollen grains has revealed a pulse of elevated UV radiation may have played a role in the end Permian mass extinction event (250 million years ago). To find out more:
Original article: Liu, F., Peng, H., John, E.A.M., Lomax, B.H., Bomfleur, B., Kent, M.S., Fraser, W.T. & Jardine, P.E. (2023) Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction. Science Advances9, eabo6102. DOI: 10.1126/sciadv.abo6102
An international team of scientists have reconstructed the longest ever record of past sunshine using pollen trapped in lake sediments collected in Ghana, Africa. The study published today in Scientific Reports enables us to understand past changes in solar input to the global system over the past 140,000 years. Previously we have had to rely upon computer models to mathematically determine past solar inputs to the Earth. “This work really is a first; being able to peer back in time to understand how the Sun has driven our global system over many of thousands of years is a very exciting prospect” said joint-lead author Dr. Phillip Jardine of The Open University.
The Sun is a key component of our natural environment, driving a multitude of processes at Earth’s surface, from photosynthesis generating energy within plants, through to global-scale circulation patterns in our oceans and atmosphere. Understanding more about how the Sun has behaved in the past, and the influence this had on Earth’s environment, will help scientists predict future climate change.
Dr. Jardine used a technique pioneered by one of his co-authors, Dr. Wesley Fraser of Oxford Brookes University, to determine past changes in solar input, specifically changes in ultraviolet (UV) radiation. Plants protect themselves from the harmful nature of ultraviolet radiation by incorporating a number of specific chemical compounds into their tissues that absorb and dissipate the energy of UV radiation. Pollen grains of flowering plants are also provided protection by these UV-absorbing chemicals, thus act as a long-term recorder of ultraviolet radiation from the Sun.
Pollen grains are readily trapped in lake sediments, where they can be preserved for millions of years. By extracting material from Lake Bosumtwi, Ghana, the pollen that was released by flowering plants thousands of years ago can be separated from the lake sediment and chemically analysed for UV-absorbing chemical compounds. It is this chemical signature within the ancient pollen grains that provides us with information about past levels of solar ultraviolet radiation.
“What we present here is a new opportunity to explore how the Earth has changed” said Dr. William Gosling (University of Amsterdam). “I am particularly excited about this because it will means that we can gain a better understanding of why vegetation changed in the past, and consequently this will allow us to anticipate better what the likely impacts of projected future climate change will be.”
A growing body of evidence suggests that plants alter their chemical composition in relation to the amount of incoming solar radiation (“insolation“) they are exposed to during life. Chemical changes are induced in order to provide protection against the deleterious effects of ultraviolet (UV) radiation; a relatively small, but important component of the total solar spectrum. UV radiation is linked with a range of detrimental biological effects, primarily stemming from damaged DNA. As sessile organisms, plants need to employ various mitigation mechanisms to prevent/reduce damage induced by UV radiation. Such mechanisms include effective DNA repair pathways, physiological adaptations, and UV-absorbing compounds. It is this last mechanism, UV-absorbing compounds (UACs), that is discussed here.
Lycopodium spore chemistry can be divided into two distinct groups; aliphatic components and phenolic components.