Sand-sized indicators of ice ages

Updated August 17, 2010 12:19:00

Most people who go snorkelling on Ningaloo reef, off the coast of Exmouth, are on holidays, soaking up the sun and trying to spot exotic tropical marine life.

However, it's all work for a group of Australian scientists, who are looking straight past the whale sharks, manta rays and coral, to the bottom of the ocean.

Dr Justin Parker from the Centre for Biodiversity and Climate Change, says just one teaspoon of sediment from the Ningaloo sea floor holds thousands of discarded shells from single-celled organisms, called foraminifera.

Dr Parker believes the shells could help map climate change patterns over hundreds of millions of years, explain the extinction of the dinosaurs and predict the timing of the next ice age.

Researchers chose the site because of its unique location between two ocean currents.

"You've got the Leeuwin currents bringing warm water and then you've got these counter-currents like the Ningaloo current and the Cape current bringing cooler water along the shoreline."

It's these competing currents that create the conditions in which coral reefs grow.

Dr Parker says Ningaloo is unique; competing currents aren't usually found on the west coast of continents.

"If you compare the West Australian coastline with, say, the Chilean coastline or the West African coastline, you don't get any coral reef tropical fauna."

He says it's this production of coral which provides a yardstick for the most significant climate changes in history; the ice ages.

"The coral reefs have actually completely disappeared during the glaciations, then reappeared during the interglacial periods, then disappeared, then reappeared.

"As the coral reefs disappear, so does the accompanying tropical marine life, like the foraminifera but there's a complete repopulation of the entire fauna during each of the interglaciations."

Telling stories

Dr Parker says Foraminifera form a calcium carbonate shell which records details of the conditions at the time that the organism was living.

"When they reproduce, the adult dies and the shell drops to the bottom of the ocean floor; you end up with billions and billions of them accumulating."

His team is now examining shell samples from tropical coral reef environments during different stages of the Pleistocene era, the period from 2.6 million years ago to about 12,000 years ago.

Dr Parker says they have found samples dating as far back as 290 million years.

"It means you get a long term record over a large part of the geological history.

"What (the researchers) are finding more and more is these large-scale cycles. Things don't just happen in pulses, there's an underlying cyclicity. We can start looking at the long-term and look at where we are in the picture of these long-term cycles."

Dr Parker hopes the shells may hold vital information about events throughout earth's history and may be able to predict information like when the next ice-age will be.

"We can look at records of mass extinctions and other major events and look at what happens during those events."

However promising the research, Dr Parker says the information contained in the shells is just a piece of the puzzle.

"We can't just rely on one source of information or data."

Topics: research, science-and-technology, exmouth-gulf-6707, wa, exmouth-6707

First posted August 17, 2010 10:15:00