When it comes to absorbing carbon you can do a lot worse than plankton. Yes, those tiny specks of flora that float around the ocean can take on a lot of carbon to thrive and grow, which means that we could use them as a reservoir of excess of carbon in the atmosphere. As we know, fossil fuels come from old plants and animals that died out millions of years ago and now we’re burning them for power, which is the biggest geoengineering project in history. A simple proposition is to reverse the process: supercharge the feeding of the phytoplankton to get them to grab the carbon and sequester it away.
To be clear the best way to deal with rising temperatures is to stop burning fossil fuels in the first place!
So we’re not talking about some wild new speculative hypothesis or an odd-ball observation from a single contested study. We’re talking about the accumulated output of hydrothermal cruises, dust-tracking satellites, floating ocean robots, sediment cores that reach back through ice ages, shipboard chemistry experiments, and decades of chlorophyll imagery. The core relationship — feed iron-starved water, and it grows more phytoplankton, in proportion to how much you feed it, and then stops when the nutrient addition stops — is about as well-established as anything in ocean science gets.
That last point deserves notice. Reversability is a key criterion for ecological safety. You want to be sure that if the intervention you’re pursuing turns out to have a negative effect, you can stop it. You wouldn’t want to risk shifting an ecosystem into a new permanent state. Here the evidence is especially clear. Phytoplankton grows as long as you keep feeding it. When you stop feeding it, it stops growing.
