The Invisible Forest: Microbes in the Sea

author: Penny Chisholm, Department of Biology, Massachusetts Institute of Technology, MIT
published: Oct. 10, 2011,   recorded: November 2006,   views: 2926

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After listening to Penny Chisholm, you’ll view pond scum or aquarium slime in a different light. In fact, Chisholm aims to instill a sense of reverence and concern for the organisms behind this phenomenon, which turn out to be blue-green algae. They’re part of a family of microbes called phytoplanktons that are essential to the earth’s health.

Chisholm sketches the history of phytoplanktons, which first emerged on earth 3.5 billion years ago, and created the oxygen in our atmosphere that made possible all other plant and animal life. “They can live perfectly well without us,” says Chisholm, “but we can’t live without them.” Energized by sunlight, phytoplankton are the ultimate recyclers. Chisholm’s research focus, Prochlorococcus, discovered in 1985, plays a supremely important role in climate control. The smallest and most abundant photosynthetic cell on the planet, it takes carbon from the atmosphere and deposits it safely to the ocean floor.

We must stop viewing all microbes as bad guys, Chisholm says, and instead, start to worry about the collective health of the organisms that regulate the world’s metabolism. Those hard at work clearing our air of global warming gases may not fare so well as the earth heats up. When ocean temperatures rise, Chisholm says, waters get more stratified, and this may make photosynthesis more difficult for the microbes. There are proposed attempts to manipulate or work around phytoplanktons – such as ocean fertilization or deep-sea injection of CO2 – but Chisholm is deeply skeptical. We may end up sucking oxygen out of the water and creating dead zones in the ocean “that release methane, nitrous oxide and other wonderful greenhouse gases that molecule for molecule, prove more powerful than CO2 in absorbing solar energy,” she warns.

Science has only just begun to study the world’s microorganisms. Just .1% of all microbes have been cultured, and who knows what other kinds of unique and essential properties we’ll find when we start looking, says Chisholm. It’s time we begin “to build the knowledge necessary to predict, regulate and sustain these vital functions of earth systems for future generations,” she says.

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