New discovery of sunscreen-like chemicals in fossil plants reveals UV radiation played a part in mass extinction events
IMAGE: ALISPORITES TENUICORPUS THE POLLEN GRAIN USED IN THIS WORK. NOTE A HUMAN HAIR IS APPROXIMATELY 70M SO THE SAMPLES ANALYSED ARE ABOUT HALF THE WIDTH OF A HUMAN HAIR. view more
CREDIT: PROF LIU FENG FROM NANJING INSTITUTE OF GEOLOGY AND PALAEONTOLOGY
New research has uncovered that pollen preserved in 250 million year old rocks contain compounds that function like sunscreen, these are produced by plants to protect them from harmful ultraviolet (UV-B) radiation. The findings suggests that a pulse of UV-B played an important part in the end Permian mass extinction event.
Scientists from the University of Nottingham, China, Germany and the UK led by Professor Liu Feng from Nanjing Institute of Geology and Palaeontology have developed a new method to detect plant’s sunscreen-like compounds in fossil pollen grains. The research has been published today in Science Advances.
The end-Permian mass extinction event (250 million years ago) is the most severe of the big five mass extinction events with the loss of ~80% of marine and terrestrial species. This catastrophic loss of biodiversity was a response to a palaeoclimate emergency triggered by the emplacement of a continental-scale volcanic eruption that covers much of modern-day Siberia. The volcanic activity drove the release of massive amounts of carbon that had been locked up in Earth’s interior into the atmosphere, generating large-scale greenhouse warming. Accompanying this global warming event was a collapse in the Earth’s ozone layer. Support for this theory comes from the abundant occurrence of malformed spores and pollen grains that testify to an influx of mutagenic UV irradiation.
Professor Barry Lomax from the University of Nottingham explains “Plants require sunlight for photosynthesis but need to protect themselves and particularly their pollen against the harmful effects of UV-B radiation. To do so, plants load the outer walls of pollen grains with compounds that function like sunscreen to protect the vulnerable cells to ensure successful reproduction.”
Professor Liu Feng adds: “We have developed a method to detect these phenolic compounds in fossil pollen grains recovered from Tibet, and detected much higher concentrations in those grains that were produced during the mass extinction and peak phase of volcanic activity.”
Elevated UV-B levels can have even further-reaching and longer-lasting impacts on the entire Earth System. Recent modelling studies have demonstrated that elevated UV-B stress reduces plant biomass and terrestrial carbon storage, which would exacerbate global warming. The increased concentration of phenolic compounds also makes plant tissue less easily digestible, making a hostile environment even more challenging for herbivores.
Summarising the groups findings Dr Wes Fraser based at Oxford Brookes University commented: “Volcanism on such a cataclysmic scale impacts on all aspects of the Earth system, from direct chemical changes in the atmosphere, through changes in carbon sequestration rates, to reducing volume of nutritious food sources available for animals.”
Photograph of the field area the fossil samples come from.
CREDIT
Prof Liu Feng from Nanjing Institute of Geology and Palaeontology
JOURNAL
Science Advances
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Dying in the Sun: direct evidence for elevated UV-B radiation at 2 the end-Permian mass extinction
ARTICLE PUBLICATION DATE
6-Jan-2023
Fossil pollen 'sunscreen' proves role of ozone depletion in largest mass extinction
IMAGE: THE IMPACTS OF OZONE DEPLETION AND ELEVATED UV-B LEVELS ON THE TERRESTRIAL ECOSYSTEM view more
CREDIT: CONOR HAYNES-MANNERING, UNIVERSITY OF NOTTINGHAM
Scientists from China, Germany and the UK led by Prof. LIU Feng from the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences (NIGPAS) have revealed that pollen preserved in 250-million-year-old rocks contains abundant compounds that function like sunscreen but are produced by plants to protect themselves from harmful ultraviolet (UV-B) radiation.
The presence of these compounds suggests that a pulse of UV-B played an essential role in the end-Permian mass extinction event.
The study was published in Science Advances on Jan. 6.
The end-Permian mass extinction event (250 million years ago) is the most severe of the big five mass extinction events, with the loss of ~80% of marine and terrestrial species. This catastrophic loss of biodiversity resulted from a palaeoclimate emergency triggered by continental-scale volcanism that covers much of modern-day Siberia. The volcanic activity drove the release into the atmosphere of massive amounts of carbon that had been locked up in Earth's interior, thus generating large-scale greenhouse warming.
Accompanying this global warming event was a collapse of the Earth's ozone layer. Support for this theory comes from the abundant occurrence of malformed spores and pollen grains that testify to an influx of mutagenic UV irradiation.
Plants require sunlight for photosynthesis but need to protect themselves and particularly their pollen from the harmful effects of UV-B radiation. "To do so, plants load the outer walls of pollen grains with compounds that function like sunscreen to protect vulnerable cells to ensure successful reproduction. Without the 'sunscreen' compounds, forests could have been sterilized, leading to the collapse of the terrestrial ecosystem," said Prof. Barry Lomax from the University of Nottingham.
"We have developed a method to detect these phenolic compounds in fossil pollen grains (Alisporites-type) recovered from southern Tibet and detected much higher concentrations in those grains that were produced during the end-Permian mass extinction and peak phase of volcanic activity," said Prof. LIU.
The researchers found an increase in UV-B-absorbing compounds (UACs) that coincided with a spike in mercury concentration and a decrease in carbon isotopes in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon- and mercury-cycle perturbations, and ozone-layer disruption.
Elevated UV-B levels exerted far-reaching and long-lasting impacts on the entire Earth system. Recent modelling studies have demonstrated that elevated UV-B stress reduced plant biomass and terrestrial carbon storage, thus exacerbating global warming.
In addition, increased concentration of phenolic compounds also makes plant tissue less easily digestible, making a hostile environment even more challenging for herbivores.
"Volcanism on such a cataclysmic scale influences all aspects of the Earth system, from direct chemical changes in the atmosphere, through changes in carbon sequestration rates, to reducing the volume of nutritious food sources available for animals," said Dr. Wes Fraser from Oxford Brookes University.
JOURNAL
Science Advances
ARTICLE TITLE
Dying in the Sun: direct evidence for elevated UV-B radiation at the end-Permian mass extinction
ARTICLE PUBLICATION DATE
6-Jan-2023
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