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(E) Caulerpa now affects the waters off the coasts of Croatia
By Nenad N. Bach | Published  11/27/2002 | News | Unrated
(E) Caulerpa now affects the waters off the coasts of Croatia

Caulerpa now affects the waters off the coasts of Spain, France, Italy andCroatia , and is spreading to parts of Northern Africa and Australia. ...


Wednesday, November 27, 2002 - 10:01:09 AM MST

Bay Area scientists combating seaweed invasion

Researchers scour local shores for non-native plant often used as packing material

By Amelia Hansen, STAFF WRITER

REDWOOD CITY -- The word "seaweed" doesn't usually strike feelings of fear or dread in the hearts of Bay Area residents, but it might if you knew what Natalie Cosentino-Manning knows.

Cosentino-Manning, a marine ecologist with the National Oceanic & Atmospheric Administration, is part of a team of scientists who have recently identified and begun to remove a non-native form of seaweed known as "Ascophyllum" -- or rockweed -- from inlets near the Seaport Conference Center in Redwood City.

The brown plant looks innocent enough, lying in between rocks and among the shoreside weeds -- and it has actually been floating around pockets of the Bay for the last 25 years or so. But Cosentino-Manning says the plant is moving into intertidal areas in larger numbers than she's seen before.

"It's never been seen colonizing like this," she said, standing in a pair of mud-covered waders. "And if you wait until it becomes significant, you've waited too long."

The seaweed is native to the East Coast and is believed to have made its way West by way of the packing trade. Ascophyllum is commonly used to pack restaurant-grade lobsters and fishing bait -- and which, presumably, is then thrown into the water or into sewer systems that make their way to the water.

Cosentino-Manning and Whitman Miller, a marine ecologist from the Smithsonian Environmental Research Center in Maryland, say the Bay is home to over 260 non-native species, many of which are not "invasive," or threatening to existing ecosystems.

While it's still unclear just how pervasive -- and potentially threatening -- the Ascophyllum may be, there's one word that keeps scientists like Manning and Miller on high alert:


In the mid-1980s, an insidious seaweed known as "Caulerpa taxifolia" began to spread up and down the Mediterranean coastline. In 2000, it hit San Diego and Orange counties in Southern California.

A beautiful but highly aggressive form of weed that can travel on ship anchors and is often sold to private aquarium owners, Caulerpa is capable of taking over marine ecosystems by driving out native grasses and the fish that feed on them.

"It's like Astroturf that can cover the entire sea floor," said Bob Hoffman, the Southern California Environmental Coordinator for NOAA.

In June of 2000, officials in Southern California identified the seaweed and began an aggressive eradication campaign a couple of weeks later. So far they have spent approximately $3 million toward eradicating the weed. While scientists say the Caulerpa is not entirely gone, it has diminished drastically and is being monitored constantly.

European authorities were not so lucky. Caulerpa now affects the waters off the coasts of Spain, France, Italy and Croatia, and is spreading to parts of Northern Africa and Australia.

While Caulerpa has not shown up in the Bay Area, Cosentino-Manning says it could still happen.

"California got lucky," she said. "If we got Caulerpa up here, I'm pretty sure it would take off. Unchecked, it could take over."

Cosentino-Manning, of course, has the same concern about Ascophyllum.

Paul Silva, a research botanist at University of California, Berkeley, who has been studying algae (the scientific name for seaweed) since 1941, was called in to make the final identification of the Ascophyllum in Redwood City.

In his opinion, it's unlikely the brown seaweed could take over to the extent that Caulerpa has.

"I don't think it's as robust," he said.

But Silva is also confused by Ascophyllum's development.

In 1979, Silva wrote a paper in which he stated there was a high probability of Ascophyllum becoming an established species in the Bay. But after watching the plant come and go since then, he concluded it was not a highly invasive species.

Still, he is intrigued by the number of plants Cosentino-Manning and Miller have been finding in Redwood City.

"I'm amazed there's that much out there," he said.

Even if the brown seaweed turns out to be less invasive or threatening than Caulerpa, Silva says Ascophyllum will continue to be a problem as long as restaurants and fishermen dump it into the water or don't dispose of it properly.

"In principle, I just don't think it's a good idea to ever dump something when you don't know what it is," said Silva.

According to Whitman Miller, whenever a non-native species is introduced to a new environment, it has the potential to bring a multitude of other organisms in with it.

He takes a wet clump of Ascophyllum in his hand and points out the small creatures -- tiny worms and snails -- attached to it.

"This stuff floats," said Miller. "If it's getting dumped into the water, it may float somewhere else and colonize. It may raft out to the outer coast."

The problem is that many people don't realize the potential problems associated with throwing a foreign seaweed into the water.

This, says Cosentino-Manning, is where education comes in. Bill Paznokas, an environmental scientist with the California Department of Fish and Game, was active in educating the public and the fishing community in Southern California in the aftermath of the Caulerpa epidemic.

Along with Hoffman and other officials at NOAA, Paznokas produced a pamphlet that explained what Caulerpa is, what to do if you find it and why you shouldn't buy it. Paznokas says they now will begin the process of setting up an educational program in this area.

"Education is key," said Paznokas. "First we have to determine how much is out there and try to get it out of the system. Then we have to start the educational process, get the word out that this is a threat to the Bay.

A large-scale public campaign helped contribute to the containment of Caulerpa in San Diego.

San Diego City Councilman Scott Peters led a local movement designed to get Caulerpa banned in San Diego and the state.

Targeting Caulerpa as the "evil weed," and "killer algae," Peters and his troops sent out letters to pet stores, aquarium owners and sea-going locals in an attempt to create awareness about the problem.

A former environmental lawyer and current member of the California Coastal Commission, Peters said their efforts resulted in San Diego being the first municipality to enact a ban on the sale of Caulerpa.

Back on the shores of Redwood City, Natalie Cosentino-Manning and Whitman Miller and two volunteers continue to comb for Ascophyllum as the fall sunlight fades.

"We need to educate people not to dump any seaweed into the water or the sewer system," said Cosentino-Manning. Miller added he would like to see warning labels placed on boxes containing Ascophyllum.

"Whatever it takes," said Miller, "we need to break the pathway of travel between the Atlantic and the Pacific."

Staff writer Ameila Hansen can be reached at 348-4301 or by e-mail at,1413,83%257E1971%257E1016035,00.html 

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