Did You Ever Wonder . . ?

Storing carbon in the ocean

Oceans absorb two billion metric tons of carbon a year, a third of the total currently emitted by human activity. Sequestering more carbon in the ocean would be one way to keep it out of the atmosphere.

The Department of Energy is investigating two approaches.

One is direct injection of liquefied carbon dioxide from shore stations or tankers. At depths of a kilometer or more, CO2 is denser than seawater and might stay on the bottom as liquid or ice.

Another approach is to "prime the biological pump" by fertilizing the growth of phytoplankton. These algae-like organisms fix carbon: when they are eaten by sea animals, bacteria transform some of their carbon to CO2, and some falls to the sea floor in waste and dead organisms.

But "in every part of the ocean there are open mouths," Jim Bishop notes. "If the excess fixed carbon is eaten by fish near the surface, the net effect is no gain." How much carbon is really sequestered by ocean fertilization? Only more research can tell.

Find out more about LBNL's ocean carbon science team


The iron hypothesis

It was no coincidence that "the SOLO carbon explorers we launched at Ocean Station PAPA caught a spurt in plankton growth after a big storm in the Gobi Desert," Jim Bishop says.

John Martin, late director of the Moss Landing Marine Laboratories, theorized that areas oddly barren of phytoplankton, although rich in nutrients, lack a trace element essential to growth: they are not seeded by windblown dust, the oceans' principal source of iron. Martin believed these regions would bloom if iron were supplied.

Atmospheric carbon dioxide is the leading greenhouse gas, but phytoplankton soaks up millions of tons of it annually. Martin boasted, "Give me a half tanker of iron, and I will give you an ice age."

Many observations support this controversial hypothesis. The most ambitious yet is the SOFeX experiment, involving ships from the Scripps Institution of Oceanography and the U.S. Coast Guard, led by scientists from Moss Landing, Woods Hole, and the Monterey Bay Aquarium Research Institute.

More about the iron hypothesis.

Did You Ever Wonder Web Site

Ernest Orlando Lawrence Berkeley National Laboratory