The Hot Zone

Microbial pump

Posted by Alison Hawkes on June 23, 2010
Category : The Oceans

The journal Science has devoted an entire issue to exploring the way the oceans are rapidly transforming in response to climate change and other factors.

It’s worth taking a peek into this extensive sweep of research; the oceans, after all, account for 70 percent of the Earth’s surface and are the least explored part of the globe. I’ll be looking at a number of the papers published in the issue largely because of the growing sense I’ve felt from an accumulation of news stories and reports that the oceans are in big trouble.

Could we see a collapse of the ocean ecosystems in our lifetimes? If we understand and treat the oceans better, could they also be savior in re-balancing the Earth’s climate?

“The ocean surface is like a planet-sized set of lungs that inhale and exhale CO2,” writes Richard Stone in a news article in the special issue (“The Invisible Hand Behind A Vast Carbon Reservoir”).

Stone explains that the oceans are a carbon sink, taking in about 2 percent more of the greenhouse gas then they release into the atmosphere. The deep ocean holds some 700 billion tons of carbon, more than all land biomass put together (600 billion tons) and almost as much as all the CO2 in the air (some 750 billion tons).

Where does it all go in the ocean? Much of it ends up in the so-called “microbial carbon pump,” whereby microbes convert the available organic carbon into a less digestible form. The microbial carbon pump (MCP) is getting a lot of attention these days in the science world as a concept that could dramatically change our understanding of carbon sequestration.

Micro-organisms in hyperthermal vents, stained to make visible under filtered light. Image courtsey of University of Washington

Micro-organisms in hyperthermal vents, stained to make visible under filtered light. Image courtsey of University of Washington

According to the paper, about 95 percent of organic carbon makes it into this indigestible and inert form, comprised of complex polysaccharides and humic acids (which absorb UV light and re-emit it as blue florescence).

The MCP could itself be a kind of conveyor belt, serving to transport and store carbon deep in the oceans. And some two billion years ago, the oceans may have held 500 times as much of the inert carbon as today.

What if we could engineer our own form to stuff the oceans with carbon? We may not even need to. Global warming, the paper states, may be stoking the MCP. Is that good? We need more answers.

-Alison Hawkes

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