Scuba Diving club,
Southern California
Sea Sabres
Two if by Sea
Invasive
Species are Changing the Ocean Environment
By Laura M. Hrastar
For decades, the
coastal United States has been under siege from an invasion of foreign animals
and plants (see second feature this issue). New species arrive daily, and in a
variety of ways. According to the Pew Oceans Commission, ship ballast water is
the primary carrier of marine species throughout the world, although
intentional introductions to control other species or mismanaged aquaculture
also often lead to the spread of new populations.
These invaders do
harm by not only wiping out native species, but also change the habitat
structure around them. Economic costs to shipping can be in the millions of dollars
when non-natives foul nets or eat commercial market fish and crustaceans
important for area industry.
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This lush stand of Caulerpa taxifolia may look pretty but,
it’s an undersea menace. The nuisance seaweed, a major problem in France, is
now cropping up in Southern California, where attempts to eradicate it
chemically have been only partially successful. |
According to Pew's
James T. Carlton, new species are being introduced into U.S. coastal waters
faster than ever, and the rate may be snowballing due to larger, more frequent
shipping operations. Ballast water is pumped into vessels to maintain
stability, and it is discharged in new ports. Linda Sheehan, director of the
Pacific Regional Offices of the Ocean Conservancy, says ballast water is the
second-most significant problem after habitat destruction nationwide.
Plants and animals
arrive as plankton (drifters), nekton (free-swimming), fouling organisms
(attached inside and on the hulls, propellers, and intake systems of vessels),
and benthos (bottom dwellers). Plankton has proven to be the heartiest, and
therefore most potent, form to arrive. Not all organisms that disperse to new
areas can establish themselves however. Reproductive biology, and the presence
of predators, competitors and parasites all play a role in a newcomer's
survival chances.
Often reported as a
maintenance problem, invading species take hold in dry dock areas such as
marine oil-drilling/production sites or floating repair structures. Others make
a home near land at nutrient run-off points from farms and power plants.
Enriched or chemically altered waters in harbors are also key areas.
The invaders'
arrival is not always accidental, however. In the past, Hawaiian resource
managers introduced the red mangrove and Philippine seaweed. In 2001, Virginia
officials released sterile Japanese oysters in Chesapeake Bay to boost the
fishing industry, a move opposed by neighboring Maryland.
Another possible
source of invasive species is aquaculture, which regularly imports exotic
organisms. "Nearly one-third of the world's seafood supply is derived from
aquaculture, and the government has reduced regulation to promote it,"
says Susan Williams, director of the University of California at Davis' Bodega
Marine Laboratory. "The aquaculture industry can help itself by protecting
cultured organisms through the control of invasive marine parasites,"
Williams says. In 1998, farmed Atlantic salmon escaped from a Pacific Northwest
fishery and entered the wild population.
At the Monterey Bay
Aquarium in California, senior marine biologist Steven Webster often deals with
exotic species in their tropical exhibits. "We ensure that invasive
species do not enter local waters by recycling water and by heavily filtering
and applying ozone or ultraviolet light to our systems."
Scientists battle
invasive species with everything from handpicking seastars/snails off the ocean
floor to mowing down salt marsh grasses. One highly debated idea is the use of
chemical control, as was tried in Darwin, Australia in 1999. There, Asian
mussels were treated and effectively wiped out with aqueous chloride, sodium
hypochloride and copper sulfate. However, much of the surrounding sea life was
also killed off. In the summer of 2000, an unsuccessful attempt in Southern
California with similar chemicals left high mortalities, but could not
eradicate, the nuisance seaweed Caulerpa taxifolia.
"Scientists
are wary of chemicals because of the lack of knowledge of all the effects they
can have on the surrounding environment," says Carlton. "Chlorination
is used when the impacts of it are thought to be less than the impact of the invading
species. Most often, target species cannot be selected out and destroyed."
Another possibility that needs further research is the use of benign
anti-fouling agents on ships. Scientists recommend that companies develop new
agents with lower chemical half-life that would have a lesser impact on other
sea life. In the future, biocontrol-- the use of one species to control
another-- may become a tool also.
On the federal
level, former President Bill Clinton created the Invasive Species Management
Plan, which went into effect in 2001. The plan charges the Coast Guard,
National Oceanic and Atmospheric Administration, the Environmental Protection
Agency (EPA) and the Department of the Interior with researching new
technologies, and it strengthens the National Invasive Species Act (NISA) of
1996. The problem with NISA, critics say, is that ballast exchange reporting
for ships is voluntary, and some vessels are exempt from participation, as is
the case with oil tankers in coastal trade and passenger vessels with "treatment"
systems. Today, a National Ballast Water Clearinghouse reports data of
transfers/invasions of species through a survey meant to oversee the rate of
compliance of the voluntary regulations.
The EPA is now
providing competitive research grants for environmentally sound control
methods. The Clean Water Act encourages states to make individual policies of
their own, and it prohibits the discharge of ballast if it contains oil enough
to cause " -- a film, sheen, discoloration, sludge or emulsion." The
International Joint Commission's (IJC) Water Quality board suggests short-term
emergency ballast chemical treatment be used. But Sheehan believes that the
EPA, Army Corp of Engineers and the Fish and Wildlife Service aren't doing
nearly enough. "We sued the government for poor regulation of endangered
species, and for non-response and weak oversight of the problems of ballast
waters," says Sheehan.
The Pew Ocean
Commission's recommendations include development of a national compulsory
ballast reporting and fouling program, as well as a rapid response system
involving alternatives to chemical treatment. Also needed, the commission says,
is a National Marine Bio-invasion Research Program, and the creation of a
nationwide education campaign, possibly under the National Sea Grant Program (a
partnership between the nation's universities and National Oceanic and
Atmospheric Administration) to increase public awareness of invasive species.
Money remains the
principal stumbling block to an effective response to invasives. Carlton agrees
with Sheehan that ballast regulation is extremely under-funded. "Our
budget is affected by the classic up-and-down slopes of politics and
funding," he says.
New
center to fight invasive species
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Posted August 19, 2003