Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists say ocean currents cause microbes to filter light

25.02.2011
Adding particles to liquids to make currents visible is a common practice in the study of fluid mechanics, one that was adopted and perfected by artist Paul Matisse in sculptures he calls Kalliroscopes.

Matisse’s glass-enclosed liquid sculptures contain an object whose movement through the liquid creates whorls that can be seen only because elongated particles trailing the object align with the direction of the current; light reflects off the particles, making the current visible to the viewer.

Researchers at MIT recently demonstrated that this same phenomenon is responsible for the swirling patterns scientists typically see when they agitate a flask containing microbes in water; many microbes are themselves elongated particles that make the whorls visible. More importantly, they say this phenomenon occurs in the ocean when elongated microbes caught in a current align horizontally with the ocean surface, affecting how much light goes into the ocean and how much bounces off as backscatter. Because many ocean microbes, like large phytoplankton, have either an elongated shape or live in communities of long chains, this orientation to ocean currents could have a substantial effect on ocean light — which in turn influences photosynthesis and phytoplankton growth rates — as well as on satellite readings of light backscatter used to inform climate models or assess algal blooms.

In a quiescent ocean, phytoplankton are randomly oriented and light filters through easily. This random arrangement is usually assumed in models of light propagation in the ocean and in satellite readings. But fluid flow can change things.

“Even small shear rates can increase backscattering from blooms of large phytoplankton by more than 30 percent,” said Roman Stocker, Professor of Civil and Environmental Engineering at MIT and lead author on a paper about this work. “This implies that fluid flow, which is typically neglected in models of marine optics, may exert an important control on light propagation, influencing the rates of carbon fixation and how we estimate these rates via remote sensing.”

Another consideration is microbial size. Very small microbes (less than 1 micrometer in diameter) don’t align with the ocean current no matter what their shape. “These very small things don’t align because they are too vigorously kicked around by water molecules in an effect called Brownian motion,” said Stocker, who studies the biomechanics of the movements of ocean microbes, often in his own micro-version of a Kalliroscope called microfluidics. He recreates an ocean environment in microfluidic devices about the size of a stick of gum and uses videomicroscopy to trace and record the microbes’ movements in response to food and current.

In this case, however, the research methodology was observation, followed by mathematical modeling (much of which was handled by graduate student Marcos, who created a model that coupled fluid mechanics with optics), and subsequent experimentation carried out by graduate students Mitul Luhar and William Durham using a tabletop-sized device.

But the impetus for the research was an observance of swirling microbes in a flask of water and a question posed by Justin Seymour, a former postdoctoral fellow at MIT. “Justin walked up to me with a flask of microbes in water, shook it, and asked me what the swirls were,” said Stocker. “Now we know.”

In addition to Seymour, who is now a research fellow at the University of Technology Sydney, other co-authors on the paper are Marcos, Luhar and Durham; Professor James Mitchell of Flinders University in Adelaide, Australia; and Professor Andreas Macke of the Leibniz Institute for Tropospheric Research in Germany.

Next steps: The researchers plan to test this mechanism in the field in a local environment suitable for experimentation, most likely a nearby lake.

Funding: Funding was provided by grants from the National Science Foundation and the Australian Research Council and by a Hayashi Grant from MIT’s International Science and Technology Initiatives Program.

Source: “Microbial alignment in flow changes ocean light climate,” by Marcos, Justin Seymour, Mitul Luhar, William Durham, James Mitchell, Andreas Macke and Roman Stocker, in PNAS Early Edition online Feb. 21, 2011.

Written by: Denise Brehm, Civil and Environmental Engineering

Denise Brehm | EurekAlert!
Further information:
http://www.mit.edu
http://web.mit.edu/press/2011/stocker-microbes.html

More articles from Ecology, The Environment and Conservation:

nachricht Gran Chaco: Biodiversity at High Risk
17.01.2018 | Humboldt-Universität zu Berlin

nachricht Dead trees are alive with fungi
10.01.2018 | Helmholtz Centre for Environmental Research (UFZ)

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: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

Im Focus: A thermometer for the oceans

Measurement of noble gases in Antarctic ice cores

The oceans are the largest global heat reservoir. As a result of man-made global warming, the temperature in the global climate system increases; around 90% of...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Gran Chaco: Biodiversity at High Risk

17.01.2018 | Ecology, The Environment and Conservation

Only an atom thick: Physicists succeed in measuring mechanical properties of 2D monolayer materials

17.01.2018 | Physics and Astronomy

Fraunhofer HHI receives AIS Technology Innovation Award 2018 for 3D Human Body Reconstruction

17.01.2018 | Awards Funding

VideoLinks
B2B-VideoLinks
More VideoLinks >>>