DEAN SENSUI / DSENSUI@STARBULLETIN.COM John Kimball took in the green expanse of plant-befouled Lake Wilson from a vantage point along Lakeview Circle on Thursday. Removing the invasive fern may take a year.

Lake cleanup
may take a year

State officials are having a
difficult time cleaning Lake
Wilson of an invasive fern

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By Diana Leone
dleone@starbulletin.com

It may take a year to contain the prolific fern that is covering much of Lake Wilson, a state official warns after leading a monthlong cleanup effort.

"It's going slowly," said Glenn Higashi, the aquatic biologist of the state Division of Aquatic Resources. He estimated that since mid-November three state and two city workers have removed about 1,000 cubic yards of Salvinia molesta from the 300-acre Wahiawa reservoir.

Despite their work, "there's more algae every time I'm out there," said John Kimball, who owns property on Lakeview Circle that overlooks the lake in three directions. "The lake is all this green mass."

Higashi said the city is considering whether it can spare an excavator or other equipment that could remove the invasive weed from the lake more quickly. Barring that, his crew will continue encircling the weed in boats with oil booms and pull it to shore.

The aquarium fern, also known as Kariba weed and aquarium watermoss, has become a problem since the beginning of the year, and aquatics personnel have been removing it manually.

But the Salvinia has been harder to remove than the water hyacinth, which plagued the reservoir four years ago, because it is smaller and breaks up more easily. Higashi recalled that getting the hyacinth under control took several years.

Salvinia, which is on the federal list of noxious weeds, has caused problems on the mainland and even blocked off Lake Victoria in East Africa, said Mindy Wilkinson, invasive-species coordinator for the state Department of Land & Natural Resources. It was removed from Enchanted Lake in Kailua and is being watched in Kawainui Marsh, although salt water there seems to be keeping it in check, she said.

Stan Wright, who has fished Lake Wilson since the 1970s, said only about a fifth of the lake's surface is clear.

He predicted that "if it keeps growing like this, you won't be able to get a boat in the water by the end of January. ... It's like trying to fish through a carpet."