Celia Smith, professor and seaweed specialist from the University of Hawai'i
Marine researchers in Hawai'i have a new weapon in the battle against alien algae: an underwater vacuum that sucks invasive algae right off the reef.
The invention, aptly dubbed the "Super Sucker," can remove up to 800 pounds of alien algae in a single hour.
“The Super Sucker is potentially the difference between watching our reefs slowly succumb to alien algae and returning them to healthy productive ecosystems,” says Celia Smith, a professor and seaweed specialist at the University of Hawaii.
Since its development in 2006, the Super Sucker pilot demonstrations have removed 50,000 pounds of algae from reefs.
Now smaller, more portable versions — called the “Super Sucker, Jr.” and the “Mini Sucker” — are making reef clean-ups in Kāne'ohe Bay, Maunalua Bay and Waikīkī easier and more efficient.
The additional machines make full-time algae removal possible, but funding from the Hawai‘i Legislature has not been delivered because of state budget cuts.
“While we wait for funding to ramp up our efforts beyond these trials, the algae tightens its choke hold on Hawaii’s reefs,” says Kim Hum, director of the Conservancy’s Hawai‘i Marine Program.
Brought to Hawai‘i for aquaculture research 30 years ago, alien algae are one of the most serious threats to Hawaii’s coral reefs today. They dominate large regions of O‘ahu’s Kāne'ohe Bay and south shore, and are also abundant on the south shores of Maui and Moloka'i.
The Super Sucker is helping to fight fast-growing invasive algae, including two particularly virulent species: Gracilaria salicornia (also known as gorilla ogo), and the gristly yellow-green Eucheuma denticulatum. Both species grow into thick, tangled mats that destroy natural habitat by smothering coral and native algal communities.
According to Cynthia Hunter, an assistant biology professor at the University of Hawai'i, both algae fill in the reef and destroy habitat for fish.
“They take a very complex habitat with nooks and crevices preferred by reef fish and flatten it,” she says. “The coral can only recover if you get the alien algae off of it.”
Eric Conklin, the Conservancy’s marine science advisor in Hawai‘i, has studied the effectiveness of the ingenious device, which is essentially a modified gold dredger that has been outfitted with a 40-horsepower diesel engine and runs on bio-diesel fuel.
"The vacuum itself is a Venturi system," explains Conklin. "That means there are no fans or blades that the collected algae pass through. This is important for two reasons: One, any marine life that is inadvertently collected can be returned. Two, alien algae can reproduce by fragmentation, so the fewer fragments we are generating during the process, the better."
The entire operation is accomplished with a five-person crew. Two divers, equipped with a four-inch round, 100-foot hose, descend below the surface, where they stuff the alien algae into the suction hose.
Aboard the barge, algae and seawater are deposited onto a large porous table, where sorters separate the by-catch and pack the algae in burlap sacks. The sacks are then delivered to local taro farmers, who have found the algae to be a superior fertilizer.
According to Brian Parscal, the University of Hawai'i operations supervisor for the project, the 800 pounds of alien algae the Super Sucker removes with two divers in an hour is equivalent to the effort generated by 150 volunteers and 10 divers.
“The other great advantage of the Super Sucker, especially the new, smaller version, is that it's portable,” he says. “It can be deployed in critical areas that are more remote, where manual removal efforts would be impractical or impossible.”
If the program can be shown to work over large areas, it could pave the way for funding to build additional Super Suckers.
“At that point, we would be in a position to attack the problem at the scale that’s really needed,” says Conklin.
But cleaning the reef of alien algae is only half the battle. Gracilaria and Eucheuma can quickly return and spread at a rate of greater than 300 meters a year.
To prevent any new growth, researchers are growing and releasing native sea urchins that feed on the alien algae and keep it in check. Healthy herbivorous fish populations can also keep algae in check, but many of these species (such as parrotfish and surgeonfish) have been over fished in Hawai‘i. Herbivore replenishment areas, such as one recently established on Maui, may keep algae growth in check once the bulk of algae is removed by the Super Sucker.
Community-based volunteer clean ups are critical to the overall effort, and Super Sucker, Jr. and the Mini Sucker are being employed at such events.
“The volunteer clean ups have been a tremendous success in educating the public and are an important complement to the Super Sucker,” says Tony Montgomery, an aquatic biologist with Hawaii’s Division of Aquatic Resources.
“But the problem is so pervasive, and the urgency so great, that we need additional tools.”
However, according to Conklin, the Super Sucker is just buying Hawaii’s reefs time. “The Super Sucker is not a replacement for better fisheries management, but it is an insurance policy that our reefs will survive while a long-term recovery plan is put into place.”
Major funding for the Super Sucker has been provided by the Conservancy's National Partnership with NOAA's Community-based Restoration Program, Hawai'i Community Foundation, National Fish and Wildlife Foundation, Hawai'i Invasive Species Council, and the National Sea Grant Program through the support of Hawai'i Senator Daniel K. Inouye.May 23, 2012