Posted on Tue, Aug. 26, 2003

New eye on ponds

NASA's View From Above Helps Bay Area's Massive Restoration of Salt Fields to Tidal Marshes

By April Lynch

As work gets under way to return the shores of southern San Francisco Bay from salt to seascape, the recovery effort is getting high-tech help from the skies.

NASA has joined the massive state and federal project to restore thousands of acres of bayside salt ponds, transforming them into tidal marsh. Using sky- and land-based sensors that measure light wavelengths, a small team of scientists from NASA/Ames Research Center in Mountain View is tracking water conditions in the ponds.

Light may not seem to have an obvious connection to water quality, but scientists have learned that the contents of a particular body of water, such as its microbial life, influence the spectrum of light that the water reflects. The microbes in the salt ponds are often what give the waters their distinctive hues, tinting everything from mustard green to fiery orange-red.

For environmental teams trying to turn a vast salt-making zone back into bay marsh, that information can be essential. It can reveal the water's health and how it is changing over time. As restoration progresses, the data can pinpoint successes and errors — and suggest better ways to restore the bay.

“We can see things a whole new way,” said Brad Dalton, a scientist on NASA's salt pond team who specializes in remote sensing technology. “You can go out there and see two ponds that look the same, except one has a bunch of birds on it and one doesn't. What do they know that we don't? Now we can find out.”

The work by the National Aeronautics and Space Administration will provide important support for one of the largest environmental recovery efforts in U.S. history, according to restoration experts.

After state and federal agencies agreed to pay $100 million to buy 16,500 acres of salt ponds from Cargill Salt earlier this year, teams of scientists have been determining exactly how best to restore them. The effort, the largest wetlands recovery project outside the Florida Everglades, could take about 30 years and cost anywhere from $200 million to $500 million.

The project offers the opportunity to re-create a vast South Bay system of tidal marshes for ducks, wading birds, salmon, harbor seals and other wildlife in numbers not seen since the gold rush of the mid-1800s. But making it work is a delicate balance.

Ponds in the South Bay have been used to make salt for roads, food and medicine for almost 150 years. Some are full of water several times saltier than the bay. Others are contaminated with industrial waste. Allowing the ocean to reclaim some areas will require that levees and pond walls be breached slowly, to avoid flooding the bay with toxic water.

The restoration is being overseen by state and federal agencies, including the California Department of Fish and Game, the U.S. Fish and Wildlife Service, and the California State Coastal Conservancy. NASA/Ames got involved, in large part, because of a lucky convergence between where the space agency is located and a particular NASA program.

NASA/Ames, which sits near the South Bay salt ponds, has a decade of experience with an aerial sensor called AVIRIS, or the Airborne Visible InfraRed Imaging Spectrometer. Mounted on a high-altitude aircraft, the AVIRIS optical sensor scans the Earth's surface, measuring light wavelengths that are both visible and invisible to the human eye.

En route to other scientific missions, AVIRIS sensors have scanned the salt ponds, sometimes as often as four or five times a year. The saved data now gives NASA's salt ponds team 10 years' worth of information about the area. More aerial findings, from both AVIRIS aircraft and satellites, will keep updating researchers on the condition of the ponds.

To make sense of the aerial data, the NASA team includes scientists who specialize in everything from geography to biology to how life forms survive in extreme conditions. The group of five researchers started visiting the salt ponds on foot, carrying a portable sensor to collect more spectral data, as well as water collection equipment. Lab culturing analysis identifies the microbes in the water, which are then matched with the light wavelength information.

When combined, those findings allow the team to decode readings from the aerial sensor and understand many of the contents of the ponds. The ponds can hold everything from brine shrimp to greenish algae and halophilic or salt-loving bacteria, which are the microbes that give some ponds a reddish cast.

The research also reveals how various microbes are faring and how their health reflects overall water quality. The sudden appearance of red captured by the sensor at one pond can be identified as matching a certain kind of halophilic bacteria, for example, showing that the water has become too salty for quick mixing with the bay.

The sensor technology can also spot other problems, Dalton said, tracking changes before the human eye can see them. For instance, the devices can help tell if certain microbes are dying off in large numbers, which might indicate problems with toxic substances such as mercury. Such toxins contaminate some ponds and must be cleaned up so they don't leak into the bay.

“If there's a sudden release of cadmium from a levee that's just been taken apart, you'll see that stress in the microbes in the water,” Dalton said. “We can use that to alert fast response teams and try to fix it. If there is a spill, we'll be watching.”

Given the huge size of the restoration area — the ponds cover about 20 miles of shoreline — aerial scans will be a critical monitoring tool, providing broader and faster information than restoration workers could obtain on land. The first phase of the NASA project lasts for two years, but the team is building a base of information that can continue to help the restoration effort for decades and plans to continue its work on the salt ponds for “a very long time,” Dalton said.

“It's such a strange place out there — a place of exquisite beauty and an industrial wasteland all at the same time,” he said. “To see something like this, on this scale, actually being attempted gives me hope that a lot of the environmental damage we've wreaked on the planet can be reversed.”

Contact April Lynch at [email protected] or (408) 920-5539.

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