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 Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

Novel breast tomosynthesis technique reduces screening recall rate

21.02.2017 | Medical Engineering

Use your Voice – and Smart Homes will “LISTEN”

21.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>