According to a recent study, a ‘tag-team’ interaction between oceans and continents millions of years ago caused widespread destruction of marine life and changed the trajectory of evolution on Earth. Researchers report that a series of environmental crises occurred between 185 and 85 million years ago, leading to mass extinctions in ocean ecosystems.
Researchers have uncovered how a “tag-team” effort between the oceans and continents millions of years ago led to severe damage to marine ecosystems and shifted the path of evolution on the planet.
Their investigation found a fresh explanation for a set of significant environmental crises known as oceanic anoxic events, which took place between 185 and 85 million years ago.
These events arose when ocean waters became critically low in dissolved oxygen.
Experts from the University of Southampton, which spearheaded the research, indicated that these occurrences triggered monumental biological changes, including extensive extinctions among sea creatures.
The study’s results were published on Thursday, August 29, in Nature Geoscience.
Tom Gernon, the lead author and a Professor of Earth Science at Southampton, stated: “Oceanic anoxic events functioned like a reset for the Earth’s ecosystems.”
“The challenge was to determine which geological forces initiated this reset.”
This research was conducted in collaboration with scholars from institutions such as the universities of Leeds, Bristol in the UK, Adelaide in Australia, Utrecht in the Netherlands, Waterloo in Canada, and Yale in the US.
Researchers delved into how tectonic plate movements influenced oceanic chemistry during the Jurassic and Cretaceous Periods, together known as the Mesozoic era.
This segment of Earth’s timeline, often referred to as the age of dinosaurs, is prominently visible along the famous Jurassic Coast in the UK, as well as the cliffs in Whitby, Yorkshire, and Eastbourne, East Sussex.
The research team utilized statistical approaches and advanced computer simulations to investigate how chemical cycles in oceans may have reacted to the disintegration of the supercontinent Gondwana, a massive landmass that dinosaurs once inhabited.
Prof Gernon further explained: “During the Mesozoic era, this landmass split apart, resulting in substantial volcanic activity throughout the globe.”
“As tectonic plates moved and new ocean floors emerged, substantial amounts of phosphorus—a crucial nutrient for life—were released into the oceans from eroding volcanic rocks.”
“Importantly, we found evidence of several waves of chemical weathering occurring on both the ocean floor and on land, which alternately disturbed the oceans.”
Prof Gernon described this phenomenon as a “geological tag-team.”
The researchers noted that the timing of these weathering events coincided with many oceanic anoxic episodes recorded in the geological timeline.
They suggest that the influx of phosphorus from weathering acted as a natural fertilizer, promoting the growth of marine organisms.
However, the researchers caution that these fertilization events came with significant drawbacks for ocean ecosystems.
Increased biological activity resulted in vast quantities of organic matter sinking to the seafloor, where it used up large amounts of oxygen, according to co-author Benjamin Mills, a Professor of Earth System Evolution at the University of Leeds.
He noted: “This process ultimately caused extensive regions of the oceans to become anoxic, or lack oxygen, resulting in ‘dead zones’ where most marine life could not survive.”
“The anoxic events typically persisted for around one to two million years and had profound effects on marine ecosystems, the effects of which are still evident today.
The organic matter-rich rocks formed during these events are now the largest source of commercial oil and gas reserves worldwide.
Aside from uncovering the origins of significant biological disruptions during the Mesozoic, the study emphasizes the catastrophic consequences that nutrient overload can have on current marine environments.
The research team explained how contemporary human actions have diminished average oceanic oxygen levels by approximately two percent, significantly expanding areas of anoxic waters.
Prof Gernon concluded: “Investigating geological occurrences provides crucial insights that can enhance our understanding of how Earth might react to future climate and environmental stresses.”
Overall, the team’s discoveries indicate a stronger connection than anticipated between the Earth’s solid interior and its surface conditions and biosphere, particularly during times of tectonic and climatic upheaval.
“It’s astonishing how a sequence of internal events can impact Earth’s surface, often with dire implications,” said Prof Gernon.
“Disrupting continents can have significant consequences for the path of evolution.”
