for National Geographic News
A giant experiment went awry at sea this month.
Shrimplike animals devoured 159 square miles (300 square kilometers) of artificially stimulated algae meant to fight global warming—casting serious doubt on ocean fertilization as a climate-control tool.
For years, scientists have proposed supercharging algae growth by dumping tons of iron into the ocean.
Iron is a necessary element for algae photosynthesis—the process by which the plants convert sunlight into energy—but it is relatively rare in the ocean.
Algae suck carbon dioxide (CO2), a greenhouse gas that contributes to global warming, out of the atmosphere. The algae then generally fall to the seafloor—sequestering the CO2 indefinitely.
About a dozen such "iron fertilization" experiments have already been done—with mixed success.
But experts have warned of unintended consequences, such as unpredictable reactions in the ecosystem.
And that's just what happened during a recent, large-scale iron dump in the South Atlantic, the Alfred Wegener Institute in Germany announced this week.
With the greenish, crystalline look of a pulverized windshield, ferrous sulfate is commonly given to iron-deficient humans.
It's also the iron of choice for boosting algae growth.
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