On their own, cyanobacteria are tiny photosynthetic organisms floating in the sea. But when they join forces, linking together into chains and then mats by the millions, they can become a threat. Before long, the bacteria change the color of the sea’s surface and even soften the wind-tossed chop. One study of cyanobacteria, also known as blue-green algae, although they are not algae, predicted that rising sea temperatures could help the already widespread creatures expand their territory by more than 10 percent. Now researchers are asking whether mats of cyanobacteria might themselves affect local sea temperatures, thus creating a powerful feedback loop.

Cyanobacteria are ubiquitous. They spew enough oxygen into the atmosphere to dictate the current mix of gases we breathe. They also compete—with great success—for nutrients such as nitrogen and phosphorus. When cyanobacteria bloom, it is often at the cost of neighboring species such as fish or other phytoplankton. So if cyanobacteria are shaping the temperature of their growing patch of the ocean to favor themselves over cold-water critters, researchers want to know how they are doing it and what to expect next, says climate scientist Sebastian Sonntag of the University of Hamburg in Germany.

Sonntag and his colleagues have adapted a computer model that describes the mixing of layers of seawater to take into account two kinds of changes produced by the cyanobacterium Trichodesmium: more light absorption and less choppy waves. The updated model predicted sea-surface warming of up to two degrees Celsius because of light absorption. The wave dampening appeared to affect local temperatures by about one degree C.

This may be the first such study of algal blooms in the ocean, says aquatic microbiologist Jef Huisman of the University of Amsterdam, who has studied light absorption by cyanobacteria in lakes. Both Sonn­tag and Huisman say they would like to ask oceanographers to measure seawater temperature where cyanobacteria grow and in nearby empty areas to test the new model’s predictions and to improve future versions.

This article was published in print as "Blue Bacteria in Bloom."

3 Comments

1. 1. amalcr 10:02 AM 3/24/12

   Dumb Obama is going to be pissed if he can't promote green algae as our future energy source for gasoline!

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2. 2. engineer.sci 08:56 PM 4/15/12

   The danger of positive feedback by cyanobacteria is just a snapshot of the complex, nonlinear natural world that is inevitably linked to the equally nonlinear world of human interrelationships.
   
   Further, it is the human element, due not so much to our unique brain as our unique ego unparalleled in the balanced communal tendency of pristine Nature, that provides an independent variable for the whole of the system. In the present system for example, cyanobacteria and temperature appear to be subject to a differential equation that links them. And although not 100% clear from within the scientific/political fog, it appears that the human decision between careful forethought for the whole, or intentional fall to blind greed, is a dynamic boundary condition.
   
   If we can come to act with mutual responsibility in just matters human, perhaps Nature itself will mirror that in a balanced calm that will insure our survival and future development.

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3. 3. Lazarus in reply to amalcr 05:49 AM 4/18/12

   Didn't you read the article? It isn't really algae.

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