Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Research: Snails were overlooked contributors to marsh destruction

16.12.2005


Weather extremes brought on by climate change could make such anomalies more common


A snail marsh. Hundreds of periwinkle snails swarm a patch of dying marsh grass in a Louisiana marsh in July 2002. Buoyed by the effects of an intense drought, otherwise harmless periwinkle snails likely killed off thousands of acres of salt marsh in the Southeast in recent years, according to new University of Florida research. The drought, which lasted from 1999 to 2001, weakened and killed marsh grasses such as cordgrass, or Spartina alterniflora, so extensively that the snails helped kill off estimated 250,000 acres of marsh stretching over 900 miles on the Gulf and southeastern coasts between 1999 and 2003. University of Florida



Buoyed by the effects of an intense drought, otherwise harmless snails likely killed off thousands of acres of salt marsh in the Southeast in recent years.

Periwinkle snails, known to science as Littoraria irrorata, normally coexist happily with salt marsh. But the drought, which lasted from 1999 to 2001, weakened and killed marsh grasses such as cordgrass, or Spartina alterniflora, so extensively that the snails moved from finishing off stressed patches to decimating large pockets of otherwise healthy marsh in concentrated waves. The result: the loss of an estimated 250,000 acres of marsh stretching over 900 miles on the Gulf and southeastern coasts between 1999 and 2003.


So says a paper set to appear Friday in the journal Science.

"It’s important to note that drought was the trigger that initiated these events – and because drought stress is becoming more extreme with global warming, events like this could become both more frequent and intense," said Brian Silliman, the paper’s lead author and an assistant professor in zoology at the University of Florida.

Salt marshes are key to healthy shorelines and oceans. They provide nurseries for juvenile fish and shellfish, filter water-borne pollutants and calm storm-driven waves, reducing the threat of hurricane-induced flood and erosion.

So scientists and citizens alike watched with alarm as the marshes started dying off from Louisiana to South Carolina beginning in 1999. Most earlier research pointed to the effects of a severe drought as the cause. The drought dried up soils, raised their acidity and boosted estuarine water and soil salinity levels -- all of which were blamed for stressing cordgrass and other marsh grasses beyond their limits.

Silliman and four other authors of the Science paper don’t dispute the drought’s impact on what scientists call "bottom-up" factors such as increased salinity. But, they say, decades of scientific tradition emphasizing only these types of influences resulted in overlooking "top down" ones – in this case, top-down controls potentially spurred by climate change.

"For ecology in general, the take-home lesson here is that increasing climatic extremes, such as drought stress, can trigger formation of grazer fronts and subsequent waves of habitat die-off in an otherwise stable ecosystem," Silliman said. "For marsh ecology, the message is even clearer: The long-standing paradigm that bottom-up forces rule is officially dead."

Climate change aside, the study also falls in line with other recent studies highlighting the role of predators or other top-down animals. "This study adds to a growing body of evidence showing strong top-down regulation of ecosystems processes, including sharks in the Gulf of Mexico and wolves in Yellowstone Park," Silliman said.

Native and abundant, dime- to quarter-sized periwinkle snails can often be seen hanging on cordgrass above the water line. Contrary to appearances, they don’t actually eat the grass, or at least not much of it. Instead, they crunch up the surface to make it easier for colonization by fungi. In a process described as fungal farming, the snails then eat the fungi.

Periwinkle snails normally coexist happily with marsh grasses. But the drought so weakened cordgrass that it began dying off. Snails then moved in, finishing off weakened and dying patches. When these disappeared and exposed mudflats emerged, large numbers of snails moved off the flats and concentrated on the edge of the die off, where healthy grass remained. This migration resulted in the formation of grazer "fronts," which attacked and destroyed more marsh in "waves" of runaway consumption, the authors write.

A team of scientists from UF, the Netherlands Institute of Ecology, Louisiana State University and Brown University reached that conclusion after observations and experiments at 12 randomly selected die-off sites in Louisiana, Georgia and South Carolina. The research was funded by Georgia Sea Grant and The Nature Conservancy.

For part of the work, the scientists simply counted snails. They discovered "extreme densities" of 400 to 2,000 snails per square meter (about 10 square feet) on the borders between healthy and dying marsh. Those numbers compared to almost no snails on exposed grassless mud flats, and far fewer snails in healthy marsh set back from the die-off border.

The researchers also removed snails from plots of healthy marsh, then enclosed the plots with wire mesh, preventing snails from reaching the grass. They put enclosures in the path of expanding die offs, as well as in remnants of healthy marsh. After 14 months, the patches were "robust and green" compared with denuded areas where snails moved through.

Brian Silliman | EurekAlert!
Further information:
http://www.ufl.edu

More articles from Ecology, The Environment and Conservation:

nachricht From the Arctic to the tropics: researchers present a unique database on Earth’s vegetation
20.11.2018 | Martin-Luther-Universität Halle-Wittenberg

nachricht Fading stripes in Southeast Asia: First insight into the ecology of an elusive and threatened rabbit
20.11.2018 | Forschungsverbund Berlin e.V.

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Nonstop Tranport of Cargo in Nanomachines

Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.

Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...

Im Focus: UNH scientists help provide first-ever views of elusive energy explosion

Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.

Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Coherence Tomography: German-Japanese Research Alliance hosted Medical Imaging Conference

19.11.2018 | Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

 
Latest News

Nonstop Tranport of Cargo in Nanomachines

20.11.2018 | Life Sciences

Researchers find social cultures in chimpanzees

20.11.2018 | Life Sciences

When AI and optoelectronics meet: Researchers take control of light properties

20.11.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>