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News Tip


September 16, 2002

For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. 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]

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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]

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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]

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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:

For the report summary and recommendations, see:

For NSF's digital government program, see:



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