Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Shape of lake basin is key factor in plankton disease epidemics in Midwest

06.05.2010
U-shaped lake bottoms promote disease 'hot spots' more than V-shaped ones

Of all the things that might control the onset of plankton disease epidemics in Michigan lakes, the shape of the lakes' bottoms might seem unlikely. But that's indeed the case, according to a paper published in the May issue of the journal BioScience.

"There are several explanations for what's going on," said Indiana University Bloomington biologist Spencer Hall, the paper's lead author.

"We're looking at the zooplankton that are infected, the fish and other creatures, the ecology, the limnology, and even the physics. Of all those explanations, the shape of the lake basins is the most powerful factor."

Also contributing to the paper are scientists from the National Science Foundation (NSF), the University of Illinois at Urbana-Champaign, the University of California at Santa Barbara and the Georgia Institute of Technology.

"This paper is a synthesis of research on a model system for the study of disease ecology," said limnologist Alan Tessier of NSF's Division of Environmental Biology.

"It combines limnological, epidemiological, ecological and evolutionary perspectives to address a general question about the occurrence of epidemics in nature," he said. "It also illustrates the value of interdisciplinary approaches to understanding the emergence of patterns in systems of complex biotic and abiotic interactions."

The disease in question is caused by a fungus in the water that infects the filter-feeder Daphnia dentifera, a water flea that plays a critical "grazer" role in many freshwater lakes in the U.S. Midwest.

Epidemics usually start in late summer or early fall.

The fungus slowly consumes the tiny crustacean's blood (hemolymph) and produces spores that fill all that remains.

For the fungal spores to make it to the next potential host, the Daphnia host's exoskeleton must be opened--and it must be opened in an area where the spores are exposed to living, uninfected Daphnia dentifera.

Whether that happens can be predicted by whether the lake bottom is V-shaped, with gently sloping sides, or U-shaped, with walls that descend rapidly away from shore.

The topography of lake bottoms has profound consequences for the lakes' ecology and movement of water that's driven by surface and subsurface temperatures.

Lakes with U-shaped bottoms have fewer near-shore nursery areas, and as a result, bluegill fish populations tend to be lower. Bluegill are a major Daphnia dentifera predator.

With fewer bluegill in lakes with U-shaped bottoms, Daphnia tend to be larger, and larger Daphnia have a higher chance of eating spores and becoming infected.

Fewer bluegill also means more Chaoborus, an invertebrate that is eaten by bluegill--and that itself eats Daphnia dentifera.

Unlike bluegill, which tend to eat Daphnia dentifera cleanly and excrete a heavy spoor that quickly sinks to the lake bottom (and probably out of the ecological picture), Chaoborus are "messy" eaters that chew up Daphnia and spit much of the exoskeleton--and spores contained in it--back out.

This invertebrate predator then spreads spores of the parasite and catalyzes epidemics.

With the scene set, all that's needed, Hall said, is a beginning.

"Physics gets the epidemic going," Hall said. "Chaoborus keeps it going."

As evening air and/or late summer storms cool the near-shore waters of U-shaped lake basins, the water sinks until it reaches waters of similar temperatures, at which point the waters move away from shore.

This creates a flow that brings nutrients (and latent spores) from shore out to the middle of the lake, where more Daphnia dentifera and Chaoborus live.

Daphnia dentifera filter feed, ingesting spores. Chaoborus eats the water fleas, breaking open husks and spewing spores into near-surface waters.

Some of the spores may sink to the lake bottom and out of the picture, but during the day, the warmth of summer and fall air keeps the near-surface waters turbulent. That creates a churning effect.

Spores are pulled upward and remain available for Daphnia dentifera to eat. Spore-containing waste produced by Chaoborus and bluegill near shore can re-feed the system in subsequent evenings, as cool air drives near-shore waters back to the lakes' centers.

"We think spores are pulled out to the water column [lake's center] by these flows, called 'gravity currents,'" Hall said. "Several physical factors inhibit gravity currents in V-shaped lakes."

The scientists believe that fungal disease epidemics seldom occur in lakes with V-shaped bottoms because dense bluegill populations prey intensely on both infected Daphnia dentifera and Chaoborus.

High predation intensity inhibits production and spread of infectious spores, thereby damping spread of epidemics in lakes with V-shaped bottoms.

"This research also gets at a bigger issue--how do the basic features of habitats drive major biological phenomena?" Hall said. "Understanding the relationship between the spatial aspects of habitats and what happens within them will be a major focus of future study."

Also contributing to the BioScience paper are Carla Cáceres and Christine Knight (UIUC), Robyn Smyth and Sally MacIntyre (UC Santa Barbara), Claes Becker (formerly of IU Bloomington, now at Sweco Environment, Stockholm), and Meghan Duffy (Georgia Tech).

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov

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

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>