Volcanic fertilization in the ocean led to severe mass extinction, scientists say – Would you be disappointed by that?
University of SOUTHAMPTON
CREDIT: DR TOM GERNON / SOUTHAMPTON UNIVERSITY [@TMGERNON]
Scientists at the University of Southampton have found that two periods of intense volcanism triggered a period of global cooling and reduced oxygen levels in the oceans, triggering one of the world’s leading extinctions. The most severe series in Earth’s history.
The researchers, working with colleagues at the University of Oldenburg, the University of Leeds and the University of Plymouth, studied the effects of volcanic ash and lava on ocean chemistry during a period of environmental change. harsh about 450 million years ago. Their findings are published in the journal Natural Geosciences.
This period resulted in a dramatic cooling of the planet, culminating in glaciations and the large ‘Late Ordovician Great Extinction’. This extinction led to the loss of about 85% of species living in the oceans, reshaping the evolution of life on Earth.
Dr Jack Longman, lead author of the study based at the University of Oldenburg and formerly a postdoctoral researcher at Southampton, said: “It is thought that global cooling is driven by an increase phosphorus input to the oceans. “Phosphorus is one of the key elements of life, determining the rate at which tiny aquatic organisms such as algae can use photosynthesis to convert carbon dioxide (CO2).2) to organic matter”. These organisms eventually settle to the seafloor and get buried, ultimately reducing the level of carbon dioxide in the atmosphere, which then causes cooling.
Dr Tom Gernon, Associate Professor at the University of Southampton and co-author of the study said: “The unanswered question is why glaciations and extinctions occurred in two different stages at this time. , about 10 million years apart. “That requires some mechanism to generate the phosphorus delivery pulse, which is very difficult to explain.”
The team determined that two particularly large pulsations of global volcanic activity, occurring in regions of present-day North America and South China, coincided very closely with two peaks during the glacial and glacial periods. strains. “But violent eruptions of volcanoes are often associated with large amounts of CO2 The release would lead to global warming, explains Dr. Gernon, so another process is responsible for the sudden cooling.
This prompted the team to consider whether a secondary process – natural decay or ‘weathering’ of volcanic material – could cause the increase in phosphorus needed to explain the ice sheets. River.
Co-author Professor Martin Palmer from the University of Southampton said: “When volcanic material is deposited in the ocean, it undergoes rapid and profound chemical transformations, including the release of phosphorus. , effectively fertilizing the oceans. “So that seems like a viable hypothesis and certainly a hypothesis worth testing.”
“This led our team to study volcanic ash layers in much younger marine sediments to compare their phosphorus content,” said Dr Hayley Manners, lecturer in Organic Chemistry at the University of Plymouth. before and after they are altered by interaction with seawater”. Armed with this information, the team had the opportunity to better understand the potential geochemical effects of vast volcanic layers from the massive eruptions of the Ordovician period.
Dr. Benjamin Mills, Associate Professor at the University of Leeds and co-author of the study.
The team found that extensive mantles of volcanic material lying on the seafloor during the Ordovician would release enough phosphorus into the oceans to drive a chain of events, including climate cooling. , glaciation, widespread reductions in ocean oxygen levels, and mass extinctions.
This could have more damaging consequences for the oceans today, scientists warn. Dr Mills warns: “Excess runoff of nutrients from sources such as agricultural fertilizers is a major cause of marine eutrophication – where algae grow rapidly and then decompose, consuming oxygen and cause significant damage to ecosystems today,” warns Dr.
Scientists conclude that in the short term large volcanic eruptions can warm the climate through CO2 emissions, equivalently, they could drive global cooling over a time scale of millions of years. Dr Longman concludes: ‘Our study could prompt a re-enactment of other mass extinctions in Earth’s history.
JOURNEYS
Natural Geosciences
DOI
RESEARCH METHODS
Simulation / computational modeling
RESEARCH SUBJECTS
Do not apply
ARTICLE TITLE
Late Ordovician climate change and extinction due to enhanced volcanic nutrient supplies
ARTICLE PUBLICATION DATE
December 2, 2021
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