The 40-mile-long Eno River runs through Orange and Durham counties
providing drinking water, recreational opportunities and biodiversity,
and it is in danger. A serious ecological and economic threat hides just
beneath the surface of the river, casting a shadow of doubt over its
future, and that of North Carolina’s many other inland waters as well.
The threat in question, however, is no more than a seemingly innocuous
weed named hydrilla.
Hydrilla is an invasive aquatic weed, regarded by the USDA as
especially harmful to existing environments and their native species. It
spreads in shallow water and forms dense mats of stems and leaves,
crowding out other aquatic plants, constricting fish movement and
depleting dissolved oxygen in the water, according to a scientific
profile from North Carolina State University.
Not only does hydrilla endanger aquatic species, which the Eno River
has many of, but it can create breeding areas for mosquitos and
seriously affect swimming, fishing, and boating, Kurt Schlimme, director
of conservation for the Eno River Association, said in an interview.
Water quality in the river is also a concern, as much water is
withdrawn for residential, but also for industrial purposes. Eno River
water is used extensively by the town of Hillsborough and rural areas of
Orange and Alamance counties.
Dale Hamby, water treatment plant manager for Orange-Alamance Water
System, Inc., said that the hydrilla has gotten visibly worse in the
last three years. “It hasn’t caused me trouble yet, but I can see where
it would,” he said in an interview.
Justin Nawrocki, graduate research assistant at NCSU, said that
because of toxic cyanobacteria that can grow on hydrilla, the hydrilla
can have devastating effects on bird populations as well. “It has
decimated the bald eagle population on [Lake Strom Thurmond] in
Georgia,” said Nawrocki in an email interview.
Nawrocki has been involved since 2009 with the Eno River project,
which has been working to find ways to combat hydrilla effectively. He
said they have been testing an herbicide called endothall to ensure that
it would not do too much collateral environmental damage to the river
if used to treat the infestation.
“It has a relatively short contact-time requirement to obtain
control, which is extremely important in a system like the Eno,” said
Nawrocki. “We feel we can safely treat the river with endothall.”
Endothall is a herbicide commonly used to control submersed aquatic
vegetation, and, according to the assessment of the EPA, not a serious
risk to public health, as long as it is applied more than 600 feet away
from where water is being drawn.
Nawrocki said that there are other herbicides being looked at as
well, and money is “a significant factor that needs to be considered
when formulating a management program.
“State funds are lacking, and hydrilla management is expensive and will be needed for many years to come,” Nawrocki said.
He said the treatment would be even tougher because of how hydrilla
grows and spreads. It easily colonizes new areas by leaving plant
fragments hidden beneath the soil and releasing buds to be carried
downstream.
The buds can remain dormant for up to a year before sprouting, and the fragments beneath the soil can last even longer.
Hydrilla was first discovered in the United States in Florida in
1960, and it was identified in North Carolina in Wake County’s Umstead
Park in 1980.
It usually spreads by attaching itself to boats, which carry it to
new areas, and it was probably first introduced to American water
systems by someone who used it as a decorative aquarium plant, Tom
Davis, Orange County water resources coordinator, said in an interview.
Now hydrilla has spread around much of the country, and it is the
target of enormous amounts of public spending. Hydrilla was discovered
in the Finger Lakes of New York last year, and now public officials
there estimate that it will cost $1 million a year for 5 to 8 years to
deal with the intrusion.
In Florida, where hydrilla is so widespread that management efforts
are usually directed only at containment, in lieu of eradication, public
agencies spent nearly $12 million in the 2010-2011 fiscal year,
according to the Florida Fish and Wildlife Conservation Commission.
“Currently it is a problem without a solution,” said Schlimme. “The
best way for folks to help is to begin questioning decision-makers about
what is being done about the issue.
“We are extremely lucky to be in a region with so many outdoor
resources and so many great organizations dedicated to protecting these
resources,” Schlimme said. “We need to be advocates for these places.”
http://campusblueprint.com/2012/09/29/invasive-weeds-threaten-north-carolinas-inland-waters/
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