Algal Blooms for Carbon Sequestration: Gluttonous Diatom May Gobble All of the Iron

Could iron be the answer when it comes to halting the influx of carbon in our atmosphere? That's a good question--and one that researchers have now examined more in depth. Scientists took a look at the possibility of fertilizing algal blooms in the hopes that they can trap carbon dioxide and offset rising global levels. What they found, though, was a gluttonous diatom.

Algal blooms aren't always a good thing. They can choke fish and leave shallow bodies of water dead and lifeless once the algae die and suck the oxygen out of the water with their decomposition. Yet iron-eating microscopic phytoplankton in the ocean may absorb enough CO2 to offset this issue. That's where ocean seeding comes in.

Ocean seeding is the process of essentially dumping iron shavings into the ocean. With more iron, more algal blooms can form which, in turn, suck out more carbon from the atmosphere. It seems like a relatively good plan, though researchers are still unsure how the process will affect the environment.

Yet one particular type of phytoplankton, a diatom, is using more iron that it needs for photosynthesis and storing the extra in its silica skeletons and shells. This, in turn, reduces the amount of iron left over to support carbon-eating plankton.

"Just like someone walking through a buffet line who takes the last two pieces of cake, even though they know they'll only eat one, they're hogging the food," said Ellery Ingall, a professor at Georgia's Institute of Technology, in a news release. "Everyone else in line gets nothing; the person's decision affects these other people."

The scientists took a closer look at these diatoms, using X-ray studies to measure the ratio of iron and silica in the plankton and surface water. After examining these tiny creatures and making some calculations, the researchers found that, conservatively, about 2.5 milligrams of iron is annually removed from every square meter of surface water in the Ross Sea. This iron is sequestered in silica skeletons on the ocean floor. This is roughly equivalent to the total amount of iron deposited annually into the Ross Sea surface through snow melt, dust and upwelling of sea water.

"This gap in our knowledge, combined with renewed interest in iron fertilization as an approach to the current climate crisis, makes it crucial that we have an improved understanding of iron cycling in marine systems," said Ingall in a news release.

The new findings show a little bit more about the cycling of iron in our oceans. This study is crucial if we're to use iron in order to fertilize the seas in an effort to sequester carbon.

The findings are published in the journal Nature Communications.