Nature Begins Rebuilding Sacramento River System : Environment: Toxic spill devastated the waterway, but enough life forms survived to start the regeneration.

Life, in its humblest manifestations, is returning to the upper Sacramento River.

Here and there, small clumps of one-cell algae are growing on the river bottom so recently flooded with poisonous pesticide. Clusters of moss cling to the rocks. And pioneers among the aquatic insects, midges and black flies and such, have begun establishing colonies among the new vegetation.

Regaining a slow and fragile hold, nature has begun the arduous and intricate rebuilding of the food chain along the 45-mile dead zone of this river, poisoned seven weeks ago when a Southern Pacific train derailed and dumped its load of pesticide into the water.

“Having this algae come back in such abundance indicates the system is on the road to recovery,” said Harry Rectenwald, a water quality biologist with the state Department of Fish and Game. “It’s a remarkable system, and we’ll get to see it all put itself back together again.”

But not all of it, not right away. On the banks of the river stand trees and bushes dying from the herbicide, known as Vapam or metam-sodium. Even where there is new growth, the leaves are damaged.

Animals that survived the chemical are now facing starvation with the loss of their primary food source--the more than 100,000 fish killed in the disaster.

“It’s a complete rebuilding and we’re starting at the bottom of the food chain,” Rectenwald said. “Some of the trout that died were 7 years old,” a venerable age for the freshwater fish.

Yet, in the midst of all the death and devastation--and contrary to initial expectations--scientists are now finding that not all life was destroyed by more than 13,000 gallons of poison that swept down the river.

Weeks after the spill, when the decaying brown mass of dead matter on the river bottom began washing downstream, biologists discovered that enough algae and moss had survived on the river bottom to provide a quick start to the recovery.

Some aquatic plants and insects survived, too, and are beginning to provide scattered sources of seeds to recolonize the river. Scientists found these survivors in small pockets along the edges of the river, in places in the riverbed where springs bubble up, and where tributaries join the Sacramento and pushed away the poison.

Nevertheless, experts caution that despite the survival, the devastation is virtually complete. They say it will be years before mature fish can re-establish themselves, providing food for the otters, eagles, ospreys and other predators that once thrived in the region.

While the simplest life forms are returning to the all-but-sterilized stretch of river, the creatures at the top of the food chain are struggling for survival.

The shortage of fish is forcing birds and mammals that once lived along the river’s length to compete for food along that small part undamaged by the spill, biologists said.

“We are seeing signs that some of those predators are crowding onto the upper two miles of the river above the spill site or onto the tributaries in search of a meal,” said Paul Wertz, a spokesman for the Department of Fish and Game. “While there may not have been a significant direct kill of terrestrial critters from the spill, there may be significant secondary effects through the loss of food.”

Wertz said nine adult ospreys have been observed feeding along the two-mile stretch of river above the spill, an area that before the disaster supported two osprey nests at most.

Researchers also have found two dead otters that apparently died of starvation. Tests will deterine the exact cause of death.

Otters eat 10 pounds of fish a day, and “when there’s no fish to eat, you don’t go over the ridge to the next river,” Rectenwald said. “You’re just left out.”

The recovery of the river will be impeded by the destruction of vegetation on its banks.

Along its 45-mile stretch, the willows have turned brown and look dead. Cottonwood trees have lost their leaves. The leaves of alders, ash trees, sedges, blackberries and dozens of other species of trees and shrubs are discolored, showing that they, too, are injured or dying.

The loss is heaviest at the water’s edge, where the plants soaked up the herbicide through their roots. Also, the chemical cloud that swept down the river canyon like a brown fog damaged thousands more plants when it came into contact with their leaves.

The devastation extends for hundreds of yards into the forest on both sides of the river. It is as if the spill had wiped out a swath of forest wider than Interstate 5, and stretching from Burbank to Santa Ana.

Like the loss of wildlife, the degree of damage to the vegetation will not be known for months or years.

Ideally, healthy vegetation shades the river, reducing the light and keeping it cool. Falling leaves provide nutrients for tiny river creatures. Roots help stabilize the riverbanks and prevent erosion. The branches shelter countless birds and animals.

“Within our study area, it’s hard to find a plant that wasn’t affected,” said Jim Nelson, a Fish and Game botanist who is heading a team surveying vegetation damage. “The truth is, we’re not clear what their fate is.”

The loss of trees and bushes, as much as the loss of wildlife, could have a serious consequence for the river and its regeneration. Some trees and bushes are sprouting new growth. But the poison--used on farms to sterilize soil--is still within the plants, so even the new leaves show signs of unnatural discoloration.

“It’s not something we’re taking lightly or that is going to be easily resolved,” Nelson said. “It’s safe to say we’ll be looking at this for years.”

This is not the first time the river has been reborn. At the end of the last Ice Age 10,000 years ago, when glaciers receded and the river melted, life returned slowly to the waterway.

Algae formed, moss grew and insects began to prosper. With enough insect life for food, the fish slowly came back, in turn becoming food for predatory birds and mammals.

This time the process will be accelerated by the plants and animals above the dead zone and by the scattered life forms that held on in the devastated area.

“Enough survived,” Rectenwald said, “to start the recolonization process within a month.”

One small haven for aquatic plants and insects was created by a few springs that bubble up in the river or right next to it, flushing fresh water into the midst of the contamination. Similarly, other river life survived where tributaries pushed the tainted water from the bank, creating small safety zones.

Still other plants and insects lived through the spill in stagnant spots along the edges of the river, where rocks fended off the pollution. After the spill, Rectenwald said, “you could pick up rocks and find little puddles and see life was OK in there.”

Ecologically, one of the more important life forms to survive was the aquatic moss, which otherwise can take years to grow back, he said. That, and the algae--which multiply quickly, as any swimming pool owner knows--have already begun providing a home for the river insects.

When a river is healthy, insects populate the bottom, hundreds per square foot. They also reproduce quickly, spending part of their lives out of the water and the rest in the river.

Once there are enough insects for a steady source of food, biologists expect that trout and other fish will begin moving in from tributaries and the area above the spill.

Even after the fish begin returning, it will take at least three years for the first new generation of trout to grow to maturity, he said.

The river was fortunate in one respect, Rectenwald said. Metam-sodium breaks down quickly, unlike other toxic chemicals, and it does not appear to be lingering in the water. Recent tests in the river and in Shasta Lake found that the poison had fallen below the detectable level of one part per billion.

For now, scientists are trying to tally the extent of the destruction to the river’s ecosystem--an assessment that will be critical in the state’s legal action to recover damages from Southern Pacific.

The studies also will shed new light on how a river recovers from such a cataclysmic event.

“There’s a tremendous opportunity for gaining scientific knowledge,” Rectenwald said. “There is a lack of experience with the loss of a river this size. We really cannot predict how fast it’s going to come back. It’s going to take some patience.”