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 Value from wastewater
16.08.2017 | Hochschule Landshut

nachricht Species Richness – a false friend? Scientists want to improve biodiversity assessments
01.08.2017 | Carl von Ossietzky-Universität Oldenburg

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Gold shines through properties of nano biosensors

17.08.2017 | Physics and Astronomy

Greenland ice flow likely to speed up: New data assert glaciers move over sediment, which gets more slippery as it gets wetter

17.08.2017 | Earth Sciences

Mars 2020 mission to use smart methods to seek signs of past life

17.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>