[APWG] Fw: USGS News Release: Exotic Hydrilla Benefits Chesapeake Bay?s Ecosystem

[Patricia_DeAngelis at fws.gov]

Forwarding this news release with an interesting twist on exotic aquatic 
species....

Patricia S. De Angelis, Ph.D.
Botanist - Division of Scientific Authority
Chair - Plant Conservation Alliance - Medicinal Plant Working Group
US Fish & Wildlife Service
4401 N. Fairfax Dr., Suite 750
Arlington, VA  22203
703-358-1708 x1753
FAX: 703-358-2276
Working for the conservation and sustainable use of our green natural 
resources.
<www.nps.gov/plants/medicinal>

- - - - - - - - - - - - - - - 

U.S. Department of the Interior 
U.S. Geological Survey 

News Release 
May 18, 2007        Nancy Rybicki        703-648-5728        
nrybicki at usgs.gov 
        Jurate Landwehr        703-648-5893        jmlandwe at usgs.gov 

Exotic Hydrilla Benefits Chesapeake Bay’s Ecosystem 

Editors:  “Long-term changes in abundance and diversity of macrophyte and 
waterfowl populations in an estuary with exotic macrophytes and improving 
water quality,” is available online in the May issue of ASLO: Limnology 
and Oceanography, v 52, pages 1195-1207. 

An exotic species of aquatic vegetation that was deemed a severe nuisance 
when it began rapidly colonizing the Potomac River, has instead benefited 
the watershed’s ecosystem, according to a study by the U.S. Geological 
Survey (USGS) published in the journal Limnology and Oceanography. The 
robust exotic hydrilla first appeared and began to flourish in the fresh 
water reaches of the tidal Potomac River just as management investments to 
reduce nutrient loads from sewage treatment plants were beginning to take 
effect.  Submerged aquatic vegetation is an important ecosystem resource 
for fish and waterfowl and it was feared that the expansion of hydrilla 
would impair the reemergence of native species, but this has not proven to 
be the case. 

“Before and during the seventeen-year period of the study, restoration of 
the Potomac has focused on reducing nitrogen loads entering the river 
system and the Chesapeake Bay,” said USGS scientist Nancy Rybicki, who 
with colleague Jurate Landwehr were curious how the emergence of hydrilla 
would affect the benefits sought for by management investments.   

Shortly after it first appeared in the Potomac in 1983, hydrilla produced 
dense vegetation masses and, in some areas, impeded boat traffic and water 
sports." More significantly, it was feared that hydrilla would interfere 
with native vegetation, which is important for waterfowl, such as black 
duck, a signature species in this area.   

Using information from annual field surveys and aerial photographs, 
Rybicki and Landwehr created a data base to document bed-by-bed which 
species of vegetation were found in different sections of the Potomac 
River system.  They recorded the percentage of total coverage and biomass 
each species attained annually.  In comparing species coverage with water 
quality composition, they discovered that, with the reduction of nitrogen 
concentration in Potomac River, hydrilla coverage expanded but so did the 
diversity of plant species found in the River. Hydrilla did not crowd out 
native species; indeed, native species increased.  In addition, hydrilla 
is a good winter food source for waterfowl communities, which have 
increased significantly over this period.   

“This research is the only long-term, quantitative study of aquatic plant 
biodiversity following the colonization of an exotic species in an estuary 
where millions of dollars are spent annually to reduce nutrient input and 
it demonstrates that exotics are not always harmful to an ecosystem,” said 
Rybicki. 

"Furthermore," Landwehr pointed out, "the methods developed for this study 
are transferable to any ecological assessments that need to merge 
remotely-sensed spatial coverage with field observations."   

The findings support current federal and state management strategies to 
improve water clarity and reduce nutrient loads to: enhance aquatic 
vegetation coverage; increase waterfowl habitat; and protect biodiversity 
of the existing native community.   

The study was conducted as part of the USGS Chesapeake Bay studies, which 
is providing integrated science to for effective conservation and 
restoration of the Bay ecosystem. The USGS is a federal partner in the 
Chesapeake Bay Program, the federal-state partnership to restore the Bay 
ecosystem. More information can be found at http://chesapeake.usgs.gov 

USGS provides science for a changing world. For more information, visit 
www.usgs.gov. 

Subscribe to USGS News Releases via our electronic mailing list or RSS 
feed. 

**** www.usgs.gov **** 

Diane Noserale
Media Relations, Eastern Region
U.S. Geological Survey
150 National Center
Reston, VA  20192
phone:  703-648-4333
fax:  703-648-4588
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.plantconservation.org/pipermail/apwg_lists.plantconservation.org/attachments/20070518/b2fcee29/attachment.html>