Article**: Oceans and Wetlands.
On February 15, 2024, a new study led by the Max Planck Institute for Chemical Research in Mainz, Germany, showed that the surface layer of tropical oceans increased oxygen levels during the Paleocene-Eocene extreme thermal event, commonly known as PETM. In this short period of geological history, the average Earth's temperature has risen by as much as 6 degrees Celsius over several thousand years
The study, published in the journal Science, used chemical and morphological measurements of foraminifera, tiny fossils preserved in marine sediments, to reconstruct the oxidation of the tropical ocean during PETM.
Source: Green Club Media.
Nitrogen isotopes are preserved in foraminifera fossils, allowing scientists to track past changes in nitrogen plug denitrification in the water. This process occurs in the ocean's most oxygen-deficient waters, known as oxygen-deficit zones. Alfredo Martínez-García, laboratory director of the Max Planck Institute for Chemistry, said: "Contrary to most expectations, our measurements show that during PETM, nitrogen plug denitrification is reduced, meaning that the ocean oxygen deficit zone has shrunk during this period of global warming. ”
The size of foraminifera fossils is key to solving the puzzle, and there are a few things we can learn by observing them. The researchers used a model to describe the lifestyle of marine organisms, linking their size to the temperature and amount of oxygen in the place where they live. Curtis Deochi, a professor of earth sciences at Princeton University, said: "Interestingly, the evidence suggests that planktonic foraminifera in the central Pacific Ocean actually became larger during PETM warming, which means that there is more oxygen on the surface of the ocean." ”
This discovery of oxygen levels in tropical oceans also provides clues to another mystery, namely changes in marine biodiversity
PETM was one of the largest mass extinctions of deep-sea life during the Cenozoic Era, spanning the past 66 million years。One of the many mysteries associated with PETM is that although this mass extinction event took place in the deeper seas, the creatures that lived in the uppermost layers of the ocean were less affected. "The transient tropical oxidation revealed by our study may help maintain the habitability of the ocean's surface, despite intense temperature stress," said Simone Moretti. However, flora and fauna in the surface ocean are still severely affected during the PETM, and it takes more than 100,000 years for these ecosystems to return to their original state, but on the time scale of human civilization, this is almost an 'eternity'. ”
Interested readers can refer to its original article:
simone moretti et al. ,oxygen rise in the tropical upper ocean during the paleocene-eocene thermal maximum.science383,727-731(2024).doi:10.1126/science.adh4893
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