[Editors] Tiny MIT ecosystem may shed light on climate change

[Elizabeth Thomson]

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Tiny MIT ecosystem may shed light on climate change
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For Immediate Release
MONDAY, DEC. 15, 2008

Contact: Elizabeth A. Thomson, MIT News Office
E: thomson at mit.edu, T: 617-258-5402

Photo Available

CAMBRIDGE, Mass.— MIT researchers have created a microbial ecosystem  
smaller than a stick of gum that sheds new light on the plankton-eat- 
plankton world at the bottom of the aquatic food chain.

The work, reported in the January print issue of American Naturalist,  
may lead to better predictions of marine microbes’ global-scale  
influence on climate.

Through photosynthesis and uptake of carbon compounds, diverse  
planktonic marine microorganisms — too small to be seen with the naked  
eye — help regulate carbon flux in the oceans. Carbon flux refers to  
the rate at which energy and carbon are transferred from lower to  
higher levels of the marine food web, and it may have implications for  
commercial fisheries and other ocean-dependent industries.

The MIT study is one of the first detailed explorations of how sea  
creatures so small — 500,000 can fit on the head of a pin — find food  
in an ocean-size environment.

Besides showing that microbes’ swimming and foraging is much more  
sophisticated and complex than previously thought, the work also  
indicates that organic materials may move through the oceans’  
microbial food web at higher-than-expected rates, via a domino effect  
of resource patch formation and exploitation, said co-author Justin R.  
Seymour, postdoctoral fellow in the MIT Department of Civil and  
Environmental Engineering (CEE).

Using the new technology of microfluidics, Seymour and colleagues  
Roman Stocker, the Doherty Assistant Professor of Ocean Utilization in  
CEE, and MIT mechanical engineering graduate student Marcos devised a  
clear plastic device about the size and shape of a microscope slide.

Depending on the organism being studied, nutrients or prey are  
injected with a syringe-based pump into the device’s microfluidic  
channel, which is 45 mm long, 3 mm wide and 50 micrometers deep.  
“While relying on different swimming strategies, all three organisms  
exhibited behaviors which permitted efficient and rapid exploitation  
of resource patches,” Stocker said. It took bacteria less than 30  
seconds, for example, to congregate within a patch of organic nutrients.

This new laboratory tool creates a microhabitat where tiny sea  
creatures live, swim, assimilate chemicals and eat each other. It  
provides the first methodological, sub-millimeter scale examination of  
a food web that includes single-celled phytoplankton, bacteria and  
protozoan predators in action.

“Rather than simply floating in the ocean and passively taking up the  
chemicals required for growth, many microbes exhibit sophisticated  
behaviors as they forage in an environment where patches of nutrients  
and resources are few and far between,” Seymour said.

Oceanographic ecological research has typically taken place at much  
larger scales because of the difficulty of measuring the behavioral  
responses of small populations of microorganisms in very small volumes  
of seawater.

“To understand how environmental fluctuations affect the ecology of  
populations, it is imperative to understand the foraging abilities and  
behavior of marine microbes at environmentally relevant scales,” the  
authors wrote.

This work was supported by the National Science Foundation.

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Written by Deborah Halber, MIT Civil and Environmental Engineering


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