A chemical process that occurs in the browning of food to give it its distinct smell and taste is probably happening deep in the oceans, where it helped create the conditions necessary for life, researchers say.
Known as the Maillard reaction, after the French scientist who discovered it, in the kitchen the process is used to create flavours and aromas out of sugars.
It converts small molecules of organic carbon into bigger molecules known as polymers.
But a research team led by Professor Caroline Peacock at the University of Leeds have suggested that on the seafloor, the process has had a more fundamental effect.
According to the experts, it has helped raise oxygen and reduce carbon dioxide levels in the atmosphere, to create the conditions for complex life forms to emerge and thrive on Earth.
The findings indicate that the reactions lock away four million tonnes of organic carbon a year.
Dr Oliver Moore, first author in the study and a Research Fellow in Biogeochemistry in the School of Earth and Environment at Leeds, said: “It had been suggested back in the 1970s that the Maillard reaction might occur in marine sediments, but the process was thought to be too slow to impact the conditions that exist on Earth.
“Our experiments have shown that in the presence of key elements, namely iron and manganese which are found in sea water, the rate of reaction is increased by tens of times.
“Over Earth’s long history, this may have helped create the conditions necessary for complex life to inhabit the Earth.”
When microscopic organisms in the oceans die, they sink to the seafloor and are consumed by bacteria.
That process uses oxygen and releases carbon dioxide into the ocean which eventually ends up in the atmosphere.
As a result of the Maillard reaction, the smaller molecules are converted into larger molecules.
The study suggests these larger molecules are harder for micro-organisms to break down and remain stored in the sediment for tens of thousands – if not millions – of years.
The scientists describe this as the preservation of organic carbon.
That long-term storage, or preservation, of organic carbon on the seabed limited the release of carbon dioxide.
This allowed more oxygen to reach the Earth’s atmosphere and limited variation in the warming of the Earth’s land surface over the last 400 million years to an average of about 5C, researchers said.
In the study, published in Nature, the scientists modelled how much organic carbon has been locked into the seabed because of the Maillard reaction.
They estimate it has resulted in about four million tonnes of organic carbon each year being locked into the seabed – the equivalent weight of about 50 London Tower Bridges.
In order to test their theory, the researchers looked at what happened to simple organic compounds when mixed with different forms of iron and manganese in the laboratory at the temperature of the seabed – 10C.
Analysis was conducted at the Diamond Light Source in Oxfordshire, the UK’s synchrotron which generates intense beams of light energy to reveal the atomic structure of samples.
It revealed that the chemical fingerprint of the laboratory samples matched those from sediment samples taken from seabed locations around the world.
Researchers suggest the lessons learned could be used to harness new approaches to tackling modern-day climate change.
Dr James Bradley, an environmental scientist at Queen Mary University of London, and one of the authors of the paper, said understanding the complex processes affecting the fate of organic carbon that is deposited on the seafloor is crucial to pinpointing how Earth’s climate changes in response to both natural processes and human activity.
He added that it is also crucial in “helping humanity better manage climate change, since the application and long-term success of carbon capture technologies relies on carbon being locked away in stable forms rather than being transformed into carbon dioxide”.