I didn't think anyone was actually going to do it!


O. vulgaris
Hi, just wondering what peoples views were on something I just heard about. I had previously heard of a theory that ran along the lines of:

If you scatter a whole lot iron dust on the surface of the ocean you will allow the phytoplankton to use it as a nutrient and cause them to rapidly multiply and form a plankton bloom. This efffectively absorbs carbon dioxide into organic form, offsetting carbon emmisions. You can then trade the carbon credits to companies that release CO2.

Now I understand that a company called Planktos is going to spread about 100 tons of iron sulphate over about 10,000 square Km of the pacific ocean to do just this (well I think in this case they're trying to prove the commercial viability of the idea).

Needless to say this has caused a strong reaction from various environmetal groups (and incidentally the US EPA) and various claims and counterclaims are being thrown round left right and centre, probably veering further from the truth as they go.

One I thought I'd specifically mention was from the company and they said that oceanic plankton levels in many places had dropped about 50% in the past few decades so what they were doing would only push the levels back up to where they should be. Does anyone know if there is any truth to that?

So, what are peoples views on this? I know little about phytoplankton population dynamics and the flow on effect on the surrounding ecosystem, etc and I don't like to make instant decisions on whether to be for or against things so I'm interested in others thoughts.


Colossal Squid
Staff member
I don't know much about the specifics, but my general assumption is that causing a major change to an ecosystem has all sorts of effects that are difficult to predict and usually destabilizing, so it sounds like a rather questionable idea. Also, although organic carbon sequestering in plant matter is frequently bandied about in these "carbon trading" schemes, at least one biologist friend of mine has pointed out that just getting plants to use the CO2 to grow isn't sufficient if when the plant dies it decays in a way that emits CO2... so there are schemes of growing bamboo and sealing them or burying them in places where they won't release CO2 in the atmosphere when they decay. Trees used as building materials that are prevented from rapid decay is good, too, and if cellulosic ethanol or algal biofuel production can "sort of" sequester it (although that's released when the fuel is burned) but I suspect that surface algae in the ocean that aren't harvested for biofuel are either consumed by animals or broken down by microbes, both of which will rapidly re-release the carbon as CO2 and defeat the whole purpose. But I don't really know that much about the fate of algae blooms, so I could be wrong, but it sounds like this is kind of a boondoggle: it'll eat CO2 for a short while to earn carbon credits, but it'll be back in the atmosphere pretty quickly, if my suspicions are correct.

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