Scientist studies death in the deep sea

By SIMON COLLINS science reporter

An Auckland scientist has found that climatic changes wiped out up to a quarter of the world's deep-sea life forms more than 600,000 years ago.

He has documented a dramatic period of deep-sea extinctions between 600,000 and 900,000 years ago, when the Earth's cycle of warming and freezing suddenly became longer and more severe.

The period is much more recent than the two other major marine extinction episodes that have occurred in the past 100 million years.

One was caused by a meteor which also killed off the dinosaurs and 80 per cent of life forms 65 million years ago, the other was a sudden warming which wiped out 30 to 50 per cent of deep-sea life forms 55 million years ago.

The scientist, Dr Bruce Hayward, said the deep sea had still not recovered from the latest blow.

"We have fewer species than we had a million years ago,' he said. "I know of no new species that have evolved in the last million years in the deep sea.

"We are now going into a period of climate change that humans appear to be influencing, and we need to be aware that human-caused change may influence the deep sea and therefore have a consequence for organisms that live there.

"Potentially they have chemicals or proteins that could be of benefit to humans. Obviously they play a part in the food systems and ecosystems of the world."

Dr Hayward was curator of marine invertebrates at Auckland Museum until the museum closed his department in 1997, and is now a research associate at Auckland University.

He has spent 30 years researching the microscopic elongated life forms which dwell in the deep oceans.

He and a colleague, Dr Hugh Grenfell, are due to finish a three-year study financed by the Government's Marsden Fund this year, and have just been awarded a further $486,000 for the next three years to determine the causes of the latest extinction period and its effects on global biodiversity.

Dr Hayward said the deep oceans were one of three parts of the Earth with the greatest diversity of living species, along with coral reefs and tropical rainforests. Because of their depth, they were barely affected by the disaster that destroyed the dinosaurs.

But the fossil record that Dr Hayward has studied shows that the deep-sea microbes were rocked by climate change in both the last two extinctions.

He said scientists were still not sure what caused the dramatic heating of the Earth 55 million years ago, which brought in oxygen-poor warm water that killed many deep-sea species.

At that time, the temperature of the deep oceans was some 10C warmer than at present.

In the past few million years, there have been successive warm and icy cycles at intervals of roughly every 40,000 years, and in the past million years every 100,000 years.

But the long-term trend in the past 50 million years has been a gradual cooling, believed to be caused in part by shifting continents which have isolated Antarctica and opened up a cold Southern Ocean all around it.

Recent global warming, caused by emissions of carbon dioxide and other "greenhouse gases" from human activities, may have reversed this cooling trend.

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