Newcastle University experts say greenhouse gases could cause marine extinction
Posted 19 May 2011, by Tony Henderson, The Journal Live, journallive.co.uk
THE mass extinction of marine life during prehistoric times could happen again due to high levels of greenhouse gases, according to research by a North East expert.
Prof Thomas Wagner, from Newcastle University, has been studying oceans that have seen depleted levels of oxygen, suffering increases in carbon dioxide and temperature.
Using core samples drilled from the ocean bed off the coast of western Africa, layers of sediment from 85 million years ago have been examined.
It was found that a significant amount of marine life was buried within deoxygenated layers of the sediment.
Prof Wagner said the results have relevance for the modern world.
He said: “We know that ‘dead zones’ are rapidly growing in size and number in seas and oceans across the globe.
“These are areas of water that are lacking in oxygen and are suffering from increases of CO², rising temperatures, nutrient run-off from agriculture and other factors.”
Researchers said their findings point to a mass mortality in the oceans at a time when the Earth was going through a greenhouse effect.
Co-author Prof Martin Kennedy, of the University of Adelaide, said: “High levels of carbon dioxide in the atmosphere and rising temperatures led to a severe lack of oxygen (hypoxia) in the water that marine animals depend upon.
“What’s alarming to us as scientists is that there were only very slight natural changes that resulted in the onset of hypoxia in the deep ocean.
“This occurred relatively rapidly, in periods of hundreds of years, or possibly even less.
“It was not a gradual, but over longer, geological time scales, suggesting that the Earth’s oceans are in a much more delicate balance during greenhouse conditions than originally thought, and may respond in a more abrupt fashion to even subtle changes in temperature and CO² levels.”
Prof Kennedy said that the doubling of the amount of carbon dioxide in the atmosphere over the past 50 years is “like hitting our ecosystem with a sledge-hammer”, compared to the very small changes in incoming solar energy (radiation) which was capable of triggering these events in the past.
“This could have a catastrophic, profound impact on the sustainability of life in our oceans, which in turn is likely to impact on the sustainability of life for many land-based species, including humankind,” he warned.
However, the geological record offers a glimmer of hope thanks to a naturally occurring response to greenhouse conditions.
After a hypoxic phase, oxygen concentration in the ocean seems to improve, and marine life returns.
This research has shown that natural processes of carbon burial kick in and the land comes to the rescue, with soil-formed minerals collecting and burying excess dissolved organic matter in seawater.
Burial of the excess carbon ultimately contributes to CO² removal from the atmosphere, cooling the planet and the ocean.
Prof Wagner said: “This is nature’s solution to the greenhouse effect and it could offer a possible solution for us.
“If we are able to learn more about this effect and its feedbacks, we may be able to manage it, and reduce the present rate of warming threatening our oceans.”
