Before Eric Conklin and fellow divers plunged into Kane'ohe Bay a few years ago to clear a reef of invasive algae, it had become nearly engulfed by the pesky seaweed.

The gorilla ogo covered roughly 60 percent to 70 percent of the reef along an 820-foot stretch off Coconut Island, displacing native marine organisms and smothering corals. The fast-growing seaweed had been a problem there for years.

Today, that section of the reef is ogo free.

It is one of the few success stories that Hawai'i scientists, conservation managers and others can point to in their seemingly never-ending battle to rid the reefs of alien seaweeds that are choking off corals and disrupting the natural balance of the nearshore ecosystems.

It is a complex problem that poses a major threat to certain reefs, is creating stinky and unsightly messes along some shorelines and is conservatively costing the economy tens of millions of dollars, by some estimates.

It also is a problem that the state is struggling to contain, especially in these tough budget times.

"Eradication is just incredibly difficult to do in marine systems," said Conklin, marine science adviser for The Nature Conservancy in Hawai'i.

The Kane'ohe effort included the debut of the Super Sucker, an underwater vacuum system that was used by Conklin and his cohorts to collect 20,000 pounds of gorilla ogo over several months in 2005 and 2006. That extraction seemed to be just enough to allow seaweed-grazing reef fish to take care of the remaining ogo, restoring a balance to that small ecosystem that hadn't been seen in years.

"All we did was give (the fish) a bit of a helping hand," Conklin said.

Another key factor was that the region at the time already was part of a marine protected area. The taking of marine life from those waters essentially is prohibited, allowing the grazing fish to munch on the seaweed without interference from fishers.

Most areas in the main Hawaiian Islands where invasive algae are a problem don't have that kind of protection, making solutions much more difficult to find.

HARBORS, BAYS AT RISK

The Super Sucker, which was developed in Hawai'i, and its spinoffs are among the multiple options local scientists, conservation managers and others potentially can tap to fight the proliferation of invasive seaweeds, five of which are causing the main problems.

At least three of them, including the gorilla ogo, were brought to Hawai'i as potential aquaculture crops in the 1970s, while another species, the spiny seaweed, is believed to have landed here accidentally on the hull of a ship traveling from Guam in 1950. It's not known how the fifth, the leather mudweed, got to Hawai'i in the early 1980s.

It generally takes about a decade or more for the seaweeds to become dominant. Interior nearshore areas, such as harbors or bays, with somewhat stagnant conditions are especially vulnerable, according to Steve Coles, a Bishop Museum research zoologist.

An out-of-balance ecosystem dominated by alien algae suggests the fish population there isn't sufficient or the nutrient level in the water is too high, or both, according to Celia Smith, a University of Hawai'i botany professor.

Scientists don't fully understand why one species will take over a reef and another won't, adding to the challenge of finding solutions. They say the most effective approach usually involves multiple strategies.

"There's almost never one magic wand," said Dwayne Minton, coral reef biologist with the U.S. Fish & Wildlife Service.

What's more, control — not eradication — usually is the most realistic goal because of all the variables affecting a marine ecosystem and the extreme difficulties in completely removing a fast-growing species, scientists say.

At Maunalua Bay in East Hono- lulu, officials will be relying partly on manual labor funded by more than $3 million in federal stimulus money to address a proliferation of leather mudweed. As many as 60 workers are expected to be hired soon for more than a year to pick the invasive algae from the bay, which is suffering from one of the largest algae infestations in the state. Over the past 18 months, volunteers working with Nature Conservancy and Malama Maunalua have removed nearly 25 tons of mudweed.

MONEY A FACTOR, TOO

The federally funded effort is believed to be the first time nationally that a large labor force will be used over a large area to control invasive algae — a situation that could provide valuable lessons for other areas dealing with infestations, Conklin said.

Scientists also are hoping to learn more about potential solutions locally when a state plan aimed at protecting specific seaweed grazers goes into effect off Kahekili on Maui. The Department of Land and Natural Resources board recently approved the first-of-its-kind plan, banning the taking of four grazing herbivore species, to address a serious seaweed infestation along a one-mile section of the North Ka'anapali coast.

Similarly, the agency is planning to ramp up efforts to raise sea urchins, a grazer, so they can be placed on reefs with a seaweed problem, according to Tony Montgomery, an aquatic biologist with the department. The idea, he said, is to have a range of possible tools that can be used in combination to control invasive species.

The motivation behind restoring ecosystem balance to the reefs is more than just environmental. Money also comes into play.

Researchers several years ago studying a North Kihei area hit by an algal bloom found the problem was costing roughly $20 million a year, mainly in depressed property values. Dead algae washing up on the Maui beaches created stench and aesthetic problems.

Largely because of the unsightly, smelly beaches, the study said property values, hotel room rates and occupancy levels dropped in the area. And North Kihei isn't the only community suffering economic hits, scientists say.

"There are very, very real costs and very large costs to ignoring this problem," Conklin said.