Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Not just the birds

08.02.2006


Introduced foxes throw a wrench in the food web



Indirect effects of predators

In an extensive study, researchers from the University of Montana, University of California - Santa Cruz, and the University of California - Davis have shown that a top predator strongly affected plants and animals at the bottom of an island food web by eating organisms that transport nutrients between ecosystems. "An introduced predator alters Aleutian island plant communities by thwarting nutrient subsidies," is published in the February issue of Ecological Monographs.


As any biologist can attest, cells, organelles, and organisms maintain specific surface to area ratios to ensure life. Similar relations have been observed in regard to an island’s size and nutrient deposition. In many cases, a small island with a large perimeter touching the sea receives more nutrients from marine ecosystems than a large island due to the differences in surface-to-area ratios. In a new study by John Maron, James Estes, Donald Croll, Eric Danner, Sarah Elmendorf, and Stacey Bucklelew, scientists have discovered that the introduction of a top predator has even affected this system.

"Our results show that the ecological effects of fox introductions extended well beyond the direct reductions of bird populations. We have clear evidence that foxes influence the terrestrial plant community and ecosystem dynamics through one particular route," state the researchers in their study.

The experiment

The Aleutian archipelago has over 450 islands in the highly productive North Pacific Ocean and Bering Sea. In the harsh northern climate, the islands are covered in maritime tundra and nutrient-impoverished soil. With no native mammals, vast populations of seabirds (29 species currently) use the area for nesting. However, over the last 100-150 years, the introduction of arctic foxes and Norway rats (Rattus norvegicus) reduced the number of birds nesting on the islands.

Arctic foxes were introduced in the late 1800’s to maintain the North Pacific fur trade, and later removed in an attempt to return the islands to their more natural states. Most of the islands are now fox-free, but the effects of their presence are still visible; birds have been slow to return to the islands to nest.

The region is its own experimental test site. The foxes were introduced to almost a quarter of the islands, about 100 total. The seabirds that inhabited the islands transported nutrients from the nearby seas to the islands via their guano, or excrements. Rich in phosphorous and nitrogen, researchers estimated that guano was reduced by over an order of magnitude on the fox-infested islands.

The reduced nutrient flow affected plants, spiders, other birds, flies, and slugs.

Nutrient status coincided with strong shifts in the structure of plant communities. Upon further experimentation, the researchers found gramanoids -- or grasses -- out-competed the slower growing dwarf shrubs and forbs. The islands with foxes had more dwarf shrubs and forbs, while those with no foxes were dominated by grasses.

Even when researchers took into account differences in island size and distances from shore, the study still showed significant differences between the fox-free and fox-infested islands.

"By disconnecting the nutritional link from sea to land, the introduction of foxes to the Aleutians has reduced or eliminated the significance of the perimeter-to-area relationship that is so clearly evident on fox-free islands," say the authors.

Previous studies have focused on trophic cascades in marine ecosystems, showing that top predators can indirectly alter plant productivity, with varying effects. Most studies on land-based ecosystems have been smaller in scale. These studies have not revealed the large community-wide indirect effects that are often found in aquatic trophic cascades, or have only shown the effects of predators from the top down to lower levels. This study shows an indirect pathway in which a predator affects a food web.

According to the researchers, the results "bolster a growing body of work indicating that island food webs are strongly subsidized by the movement of nutrients from adjacent productive waters onto less productive land."

Annie Drinkard | EurekAlert!
Further information:
http://www.esa.org

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: First diode for magnetic fields

Innsbruck quantum physicists have constructed a diode for magnetic fields and then tested it in the laboratory. The device, developed by the research groups led by the theorist Oriol Romero-Isart and the experimental physicist Gerhard Kirchmair, could open up a number of new applications.

Electric diodes are essential electronic components that conduct electricity in one direction but prevent conduction in the opposite one. They are found at the...

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...

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

Helping to Transport Proteins Inside the Cell

21.11.2018 | Life Sciences

Meta-surface corrects for chromatic aberrations across all kinds of lenses

21.11.2018 | Power and Electrical Engineering

Removing toxic mercury from contaminated water

21.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>