Sept. 30 (Bloomberg) -- The storms that engulfed Sydney in orange and yellow clouds last week may be a boon for sea life and lower carbon dioxide levels after as much as a million tons of dust were dumped into Australia’s oceans, providing a rich supply of food for algae.

The gale-force winds that ripped through Sydney may have dumped the iron-rich topsoil from Australia’s drought-ridden Outback into the Tasman Sea and Pacific Ocean, where it would have been absorbed by algae, said Craig Strong, a coordinator for DustWatch, a research and monitoring agency.

The infusion of so much soil into the ocean may prove a veritable feast for plankton that feed on algae and are then eaten by fish, crabs and krill. The tiny plants also absorb carbon dioxide from the air and water, which may reduce greenhouse gas concentrations.

“It’s been pretty well established that if iron is available, then it will lead to phytoplankton blooms,” said Heiko Daniel, a lecturer in agronomy and soil science at the University of New England in New South Wales. “And they take up carbon dioxide from the atmosphere.”

Strong winds caused by a low pressure system whipped up topsoil parched by years of drought from the Australian outback to cause the dust storm, the Bureau of Meteorology said on Sept. 23. The cloud, more than 500 kilometers (310 miles) wide and 1,000 kilometers long, was the largest to hit Sydney since the 1940s and was driven from the interior by gale-force winds, the Bureau of Meteorology said.

One millimeter to two millimeters of topsoil may have been stripped from Australia, meaning as much as 1 million tons of earth may have been thrown into the air, Daniel estimates.

Air Quality

Concerns about respiratory problems and soil erosion have subsided. The air quality index for Sydney fell back to the mid- 40s, or “good,” a day after the Sept. 23 storm sent the gauge to almost 3,400, with anything above 200 deemed potentially hazardous, the New South Wales Environmental Protection Agency’s Web site showed. A second dust storm on Sept. 26 inched the index up to a little more than 300.

“The dust storm did clear very quickly,” said Guy Marks, a respiratory physician and clinical professor at the University of Sydney. “There are no signs of long-term effects.”

The EPA dismissed speculation the dust may have contained radioactive material from uranium mines in Woomera, near the Lake Eyre basin where it originated.

“It’s definitely not radioactive,” spokeswoman Liza Cassidy said. “It’s very good quality soil, because it’s top soil.”

Agriculture Impact

The loss of topsoil from Australia’s interior is unlikely to harm agriculture, as the area involved is sparsely stocked, semi-arid rangeland, said Daniel from the University of New England.

“It’s not rich farmland,” he said. Farmers may have to consider alternative areas for their flocks to graze, which the drought was likely to force them into doing, Daniel said.

The dust storms also brought “patchy” rain to New South Wales state, making them a “net positive” for the region’s grain crops, Brett Stevenson, managing director of Market Check, said on Sept. 23.

To contact the reporter on this story: Nichola Saminather in Sydney at nsaminather1@bloomberg.net;

Last Updated: September 29, 2009 21:02 EDT