September 16, 2002
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Editor: Josh Chamot
Contents of this News Tip:
Without Blue
Crabs, Southern Salt Marshes Wash Away
The blue crab harvest needs to be scaled back immediately,
say biologists.
Their study suggests that over-harvesting of blue crabs
may be triggering the colossal die-off of salt marshes
along the southeastern United States.
Southern salt marshes stretch from Chesapeake Bay to
the central-Florida coasts and are some of the most
productive grasslands in the world. The marshes temper
coastal flooding, filter mainland run-off and act
as nurseries for commercially important fish and other
species. The marshes also protect barrier islands,
which buffer shorelines from erosion.
In experiments along the Virginia and Georgia coasts,
Brown University researchers supported by the National
Science Foundation (NSF) manipulated local populations
of marsh animals. The scientists found that when blue
crabs disappeared from a salt marsh, their main prey
- periwinkle snails - flourished. Once free of predation
from blue crabs, the snails ate all of the cordgrass
in the marsh.
Cordgrass dominates the southern marsh, anchoring it
and providing its animals with habitat. Without the
plants to bind sediment and protect wildlife, the
salt marsh ecosystem collapses, the scientists found.
In fact, the study shows that overgrazing by periwinkle
snails will convert a southern salt marsh into a barren
mudflat within 8 months.
"Cut back the blue crab harvest," said project member
Mark Bertness, "because even if we're half right,
the results of over-harvesting could be disastrous."
Hundreds of miles of southern salt marshes have died
in recent years, particularly in Louisiana and Florida.
Bertness and colleague Brian Silliman surveyed several
of the dead and dying marshes and found relatively
high densities of periwinkle snails, but few blue
crabs. The researchers believe the effects shown in
the experiments may already be at work in the southern
marshes.
For more than 50 years, ecologists assumed that the
1/2- to 3/4-inch long, black or gray periwinkles ate
only dead and dying plant materials in southern salt
marshes. But Silliman and Bertness found that unchecked
populations of the snail readily ate living cordgrass.
Moreover, the greater the nitrogen content of the
grass (nitrogen is the prime nutrient in mainland
run-off), the more attractive the grass is to the
periwinkles.
The study may cause upset among ecologists. For decades,
the prevailing model of marsh ecology was that bottom-up
forces, such as currents and nutrient flow, primarily
determined plant productivity. But the new study indicates
that a top-down process - the control of grazers (snails)
by consumers (crabs) - chiefly establishes the growth
of marsh grass.
According to the researchers, this top-down phenomenon
"implies that over-harvesting of snail predators,
such as blue crabs, may be an important factor contributing
to the massive die-off of salt marshes across the
southeastern United States." [Cheryl Dybas]
Top of Page
Ocean Drilling
Program Explores Climate Change in the Southeast Pacific
The sea floor of the Southeast Pacific is one of the
least studied regions on Earth. Recently, scientists
representing nine nations set sail for the region
from Valparaiso, Chile, aboard the drillship JOIDES
Resolution, and returned with new information
about climate change.
Part of the international Ocean Drilling Program (ODP),
the researchers visited sites ranging from windy regions
off southern Chile to the steamy Gulf of Panama. On
ODP's Leg 202, JOIDES Resolution roughly
followed the path taken by Charles Darwin 170 years
ago on HMS Beagle.
The ODP team targeted sites that recorded global and
regional climate information, "to test competing ideas
about where the triggers for major change lie," said
Alan Mix of Oregon State University, one of the team
leaders. "We're looking at climate effects on several
scales, from the slow tectonic uplift of the ancient
Andes to abrupt climate shifts within human history.
We've never had the right samples before - now we
do," said Mix.
After weathering 40-mile-an-hour storm winds off southern
Chile, the team recovered sediments that record changing
ocean conditions - at intervals of 40 years or less
- through the more than 100,000 years of the last
ice-age cycle.
Researchers once believed the last 10,000 years, an
interval known as the Holocene, has been a time of
stable climate that nurtured the growth of civilizations
throughout the world. However, new data suggest that
Holocene climate was more dynamic, and the results
from Leg 202 confirm this variability in the South
Pacific.
"We now have evidence that the Westerly winds, and
the torrential rains they bring to the southern Andes,
oscillated in both their strength and position," said
sedimentologist Frank Lamy of the University of Bremen
in Germany. "These changes appear to be linked to
rapid climate oscillations of the ice age," he said.
ODP is an international partnership, comprised of
scientists and research institutions that study the
evolution and structure of the Earth. The program
is principally funded by the National Science Foundation
(NSF), with substantial contributions from its international
partners. [Cheryl Dybas]
Top of Page
Evolutionary
Origins of "Red Tide" Life Support Revealed
Researchers have uncovered a critical link in the evolution
of the tiny plant that causes harmful algal blooms,
commonly known as "red tides." The blooms can be ecologically
and financially costly, killing millions of fish along
the U.S. Atlantic and Gulf coasts each year.
Debashish Bhattacharya, a biologist at the University
of Iowa, is studying single-celled plants called dinoflagellates
and determining the evolutionary origin of tiny cell
components known as plastids, which are responsible
for photosynthesis.
"The dinoflagellates are some of the most economically
important single-celled organisms because of the toxic
red tides they can cause that result in fish and shellfish
mortality," says Bhattacharya, "Our work lays the
foundation for understanding the basic biology of
these species."
Bhattacharya and his colleagues determined that the
dinoflagellates "stole" their photosynthetic ability
from another algal group, the haptophytes. The researchers
believe that similar processes have driven the origin
and diversification of the huge, diverse population
of photosynthetic, single-celled organisms on our
planet.
NSF and the U.S. Department of Agriculture recently
awarded Bhattacharya and his group a grant to generate
a genomic database for the toxic dinoflagelate Alexandrium
tamarense. [Cheryl Dybas]
Top of Page
NRC Report
Touts Government Investments in Information Technology
Research
According to a recent report from the National Research
Council (NRC), government agencies have a unique ability
to invest in long-term research for improving information
technology (IT). Such research would benefit computer
science and greatly improve the efficiency of digital
government programs.
The NRC's Committee on Computing and Communications
Research to Enable Better Use of Information Technology
in Government drafted the report, "Information Technology
Research, Innovation, and E-government," at the request
of NSF.
NSF manages a digital government program in its Computer
and Information Sciences & Engineering directorate
and is at the forefront of federal digital government
efforts.
The NRC committee explored how IT research can improve
existing government services, operations and interactions
with citizens. The committee also highlighted ways
to foster new uses of IT in digital governance.
The committee stated that while the private sector
plays a key role in digital government research, government
itself is "a long-term, patient investor in IT research,
particularly with respect to research results that
have broad value."
The most widely recognized example, according to the
report, is the development of the Internet suite of
protocols, along with the establishment of processes
for evolving them. "A significant portion of these
technologies and standards resulted directly from
ongoing, far-sighted government investment by a number
of research agencies," the report states.
The committee cited a range of areas in which government
research would be "particularly likely" to improve
digital government - many of which overlap with existing
NSF IT research programs and priorities - such as
e-commerce technologies and simulation tools that
would improve government planning and crisis management.
To see an electronic version of the report, published
by the National Academy of Sciences, see: http://www.nap.edu/books/0309084016/html
For the report summary and recommendations, see: http://books.nap.edu/books/0309084016/html/1.html#pagetop
For NSF's digital government program, see: http://www.digitalgovernment.org
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