Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lowly Icelandic midges reveal ecosystem's tipping points

06.03.2008
The midges that periodically swarm by the billions from Iceland's Lake Myvatn are a force of nature.

At their peak, it is difficult to breathe without inhaling the bugs, which hatch and emerge from the lake in blizzard-like proportions. After their short adult life, their carcasses blanket the lake, and the dead flies confer so much nutrient on the surrounding landscape that the enhanced productivity can be measured by Earth-observing satellites.

Now, however, the midge Tanytarsus gracilentus and its periodic, sky-darkening hatches are giving scientists an opportunity to assess how the slightest environmental perturbation can tip the precarious balance of an ecosystem and push it into altered states with unknown consequences. Writing this week in the journal Nature, a team led by University of Wisconsin-Madison zoologist Anthony Ives describes an ecosystem population dynamics model built on the flies of Lake Myvatn, showing how even slight human-induced changes can irreversibly alter the balance of nature.

"If our model is correct, the magnitude of these cycles should be sensitive to even the smallest changes in the hydrology of the lake," explains Ives, who conducted the research in collaboration with Árni Einarsson and Arnthor Gardarsson of the University of Iceland, and Vincent A. A. Jansen of Royal Holloway, University of London.

The new study is important because it suggests the possibility of constructing powerful models that scientists can use to assess what may occur as a result of both natural changes and human-induced changes such as those linked to global warming.

"It doesn't take much noise to cause big changes in the pattern," says Ives of phenomena, natural or human-induced, that can tip the balance of an ecosystem. "Even small amounts of environmental noise cause very different biological processes to dominate. And even if you understand the causes, you can't predict the effects."

In short, the study implies that humans are very likely and unknowingly imposing profound, unpredictable and irreversible changes on ecosystems of all kinds with very little effort.

Lake Myvatn, which means "midge lake" in Icelandic, makes a perfect laboratory for studying such environmental change. The algae-munching midge Tanytarsus gracilentus alone makes up two-thirds of the herbivores in the lake's biomass and is an important food source for birds and fish. But the populations of the midge fluctuate dramatically: "They fluctuate in abundance by six orders of magnitude; in some years you hardly see any, while in others you have to fight not to inhale them," according to Árni Einarsson who directs the Myvatn Research Station.

"The odd thing about the Myvatn midges," Ives adds, "is that the fluctuations are not random, but neither are they regular."

The model developed by Ives and his colleagues reveals an exotic mathematical property known as "alternative dynamical states." In short, the midges of Myvatn can appear in cycles of great and regular abundance, or at stable high abundances, and natural variables or "noise" such as temperature or wind can unpredictably push the dynamics between these alternative patterns.

"A practical, and serious, implication of these dynamics is that they make midges potentially susceptible to even minor disturbances," says Ives. "The magnitude of the fluctuations could be highly sensitive to disturbances that affect how low the populations crash during the cycling phase. In the last 40 years, the fluctuations in midge populations seem to have become more extreme. "

So extreme, Einarsson notes, that the Lake Myvatn fishery, a resource used by local farmers for 1,000 years has collapsed. "The fluctuations in midge populations became so extreme that the fish populations couldn't cope during midge crashes. Basically, the fish ran out of food."

The model developed by Ives' team implicates dredging in the lake, an operation initiated in the 1960s and now abandoned that was coincident with changes in the fluctuation of midge populations.

"Our model suggests that this dredging could, in principle, have caused greater fluctuations in midge populations," according to the Wisconsin biologist.

Although there are only a few species in the case of Lake Myvatn, the fragility of their dynamics makes the lake's ecosystem and the forces at play a valuable model for understanding discrete ecosystems of all kinds.

"These forces involve few species," notes Ives, "yet they have huge ramifications. They become an important test bed for looking at ecosystems in general."

Anthony R. Ives | EurekAlert!
Further information:
http://www.wisc.edu

More articles from Ecology, The Environment and Conservation:

nachricht Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF

nachricht Dry landscapes can increase disease transmission
20.06.2018 | 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: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

Im Focus: Chemical reactions in the light of ultrashort X-ray pulses from free-electron lasers

Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.

Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

Nano-kirigami: 'Paper-cut' provides model for 3D intelligent nanofabrication

16.07.2018 | Physics and Astronomy

New players, standardization and digitalization for more rail freight transport

16.07.2018 | Transportation and Logistics

Researchers discover natural product that could lead to new class of commercial herbicide

16.07.2018 | Agricultural and Forestry Science

VideoLinks
Science & Research
Overview of more VideoLinks >>>