UNDERWATER VAC INHALES ALIEN ALGAE
09.28.07 - Leído 106 veces. Enviar esta notaTracy Staedter
Alien algae are infesting and killing some of Hawaii’s coral reefs at an unprecedented rate. But a new underwater vacuum cleaner is helping curb the growth
WASHINGTON, US; September 28, 2007.- Dubbed the Super Sucker, the machine can hoover up to 800 pounds of the thicket-like algae in an hour, which should give reefs a fighting chance of recovery.
“Now that we have cleared the algae, we are starting to see new coral recruits come in. It’s going to be a process of recovery that takes years,” said Eric Conklin, marine science advisor at the Nature Conservancy in Honolulu.
Recuperation wouldn’t even be necessary had humans not introduced the aliens to Oahu’s Kaneohe Bay in the first place. Back in the 1970s, researchers decided to grow two kinds of non-native algae — Gracilaria salicornia, also known as gorilla ogo, and Eucheuma denticulatum — as part of an experiment in aquaculture.
These underwater plants, which are harvested commercially in other parts of the world, contain compounds that can be extracted and used as thickening agents in everything from toothpaste and shaving cream to whipping cream and nonfat ice cream.
But in Hawaii, the alien algae have few natural predators. When the aquaculture scheme was eventually abandoned, the algae grew to uncontrollable proportions.
“Not only does it kill the coral, but it denudes all of the three-dimension space,” said Jennifer Smith, a post-doctoral researcher at the University of California, Santa Barbara, and an expert in coral reef ecology.
“It reduces species diversity and leaves a really homogenous, barren, single-species-dominated environment in its wake,” said Smith.
Efforts to remove the algae began in 2002 with a program to recruit community-based volunteers. The volunteers snorkeled or dove along reefs close to shore, removing the mats of algae by hand. But it was clear that a more aggressive plan was needed.
Researchers and conservationists from the University of Hawaii, the Nature Conservancy, and the State Department of Land and Natural Resources met to discuss a solution. Eric Co, the conservancy’s marine coordinator, followed through on an idea of an underwater vacuum. Called Super Sucker, Sr. (a recently built junior version is smaller and can be transported to other parts of the island by truck), the device is a modified gold dredger set up on a 13 by 25-foot pontoon barge housed at the Hawaii Institute of Marine Biology.
The vacuum itself is just powerful enough to suck up the algae but not so strong that it inhales all other life forms in its path. And just in case, the device is built so that the water, algae and other collected items do not pass over fans or blades. This way, if a small fish, sea cucumber or bit of coral get inside the 75-foot-long hose, they will not be damaged.
After the water and algae flow up the hose, it spills out onto a mesh-lined sorting table, where the algae are pulled out and packed into bags. Any inadvertent bycatch is returned to the reef unharmed. The algae is given free to local farmers, who use it as compost on crops.
Between community efforts and the Super Sucker, hundreds of tons of the invasive species have been removed, but that doesn’t guarantee their eradication.
Even a tiny bit of algae left behind could grow in a few years with devastating consequences. So the team continues to monitor reefs they have cleared. They’d like to measure how long it takes the algae to come back.
They’re also looking at ways to stem its growth. For example, introducing native sea urchins onto reefs could help keep the invasive weed under control.
“We’re getting to the point now where we feel like we have a good suite of tools to remove alien algae. And we are just getting underway with trying to establish comprehensive control programs on the other islands,” said Conklin.
(Discovery News)
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