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Uprooting river invader


Scientists fight spread of plant in the San Marcos

Houston Chronicle (09/20/2003)

By John W. Gonzalez

SAN MARCOS — Perhaps it was someone moving out of town who didn’t want to tote an aquarium along.

Without thinking of the consequences, that person may have dumped the fish tank’s entire contents, plants and all, into a storm drain.

Experts aren‘t exactly sure how it was introduced, but a decade after it was first noticed by botanists, a common aquarium plant that overpowers native species in the wild has commandeered a delicate segment of the San Marcos River.

With an underwater vacuum device used in gold mining, ecologists in diving gear are escalating the battle against the non-native Sri Lankan water trumpet plant. Rapid spread of the plant in a spring-fed stretch of the river east of town is threatening two endangered native species — Texas wild rice and the fountain darter fish — experts said last week.

Volunteer efforts to control the aggressive species with manual uprooting proved to be inadequate. Now federal, state and other entities have pooled resources to reduce the spread of water trumpets before the plant changes the river‘s character.

The plant, cryptocoryne beckettii , a popular aquarium addition known as “crypto,” also is playing havoc in Florida, officials said, noting that in both states the plant flourishes only in spring-fed waters.

Officials are hopeful that despite tenacious roots that can sink more than 2 feet below river bottom, the plant will not take hold down river in deeper waters with fewer springs. But they‘re taking no chances.

Volunteers from the U.S. Fish and Wildlife Service, Guadalupe-Blanco River Authority, Guadalupe Blanco River Trust and Texas State University at San Marcos stepped up the eradication effort last week. Workers relied heavily on the underwater suction device, mounted on a mini-barge, which gently extracts a crypto plant without leaving buried root fragments that continue growing.

The effort focused on bank-to-bank patches of water trumpet growing closest to wild rice and fountain darters, officials said.

“ The one that we’re concerned about is Texas wild rice,” said Todd Votteler, the river authority‘s director of natural resources. “The area around the San Marcos River is the only place it‘s still found, and the water trumpet likes to occupy the same habitat.”

“ What we’re afraid of is, this (water trumpet) is going to get established and the wild rice is going to be pushed out,” Votteler said as he stood waist-deep in the river, three miles downstream from its origins near the university.

“ The fountain darter relies on certain plants that it eats and uses for its habitat. The water trumpet could replace some of those plants that it depends on,” Votteler added.

Although the plant was spotted a decade ago, early efforts to contain it proved futile, he said.

“ They didn‘t realize how fast it multiplies. In one year, it will increase its area by about 80 percent,” Votteler said.

Crypto has become the dominant river plant in the area targeted for its removal. It has no natural enemies, and there‘s no evidence the river has ever dried up here, so there‘s little chance the plant would die off from lack of water.

The only solution is gentle removal that doesn‘t disturb commingled native species, Votteler said, adding that federal experts “had to create this procedure. They came up with this fairly ingenious idea of getting this dredge that people use to dredge gold out of rivers in Alaska. It sucks out the sediment and the roots of the water trumpet.”

Volunteers then sift through the sludge, remove the plants for destruction and return the sediments to the river. Eight federal permits, which took a year to obtain, were required for the operation, Votteler said.

If the dredging technique had been used in 1993, it wouldn‘t have taken long to stop the plant‘s spread, Votteler said.

“ Now it‘s going to take months,” he said.

Fish and Wildlife Service botanist Paula Power said the cleanup progresses at the rate of about 12 square yards a day, though the work is only conducted a day or two each week.

In 1998, five years after the plant was first noticed, its range in the San Marcos was mapped, and its area was estimated at 240 square yards.

“ Between 1998 and 2003, it went up to about 2,000 square meters” (or 2,400 square yards), Power said.”About two miles of the river is infested. And it could spread to other spring-fed creeks and rivers. We hope that if people see it in other places they’ll tell us.”