Marine Phytoplankton Absorbing 2.5 GT Less CO2 Than Previously Thought

Even phytoplankton are letting us down when it comes to global warming. These microscopic ocean-dwelling plants, which were thought to be gobbling up atmospheric carbon dioxide, are apparently not doing as well as was hoped.

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Peter Strutton of Oregon State University and colleagues studied phytoplankton fluorescence in the tropical Pacific using data from 12 years and 58,000 kilometres of ship transects and found that the phytoplankton are making far less chlorophyll than expected. They reason that in nutrient-poor waters like the tropical Pacific, phytoplankton are starved of nitrates and iron. Because of this they produce a pigment-protein complex that is not chlorophyll but shows up just as green in satellite images. They calculate that this means 2.5 billion tonnes less CO2 is being absorbed each year than was thought (Nature, vol 442, p 1025).

From issue 2567 of New Scientist magazine, 30 August 2006, page 15

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http://www.newscientist.com/article/mg19125676.000-ocean-plankton-absorbs-less-cosub2sub-than-expected.html

I'm just imagining a few trillion little guys floating in the ocean, all simultaneously pulling a Cartman and saying "Screw you guys, I'm going HOME!"

I'm sure all of you are feeling much more enlightened and elucidated after this brilliant piece of input. :P

Dumping iron sulphate in the ocean to cause plankton blooms might not seem an eco-friendly way to tackle global warming. But, according to the most extended trial of the technique so far, it could prove an effective one.

The outcome of the trial in the Southern Ocean, which surrounds Antarctica, was published in last week's Science. It suggests that each atom of iron added to the sea could pull between 10,000 and 100,000 atoms of carbon out of the atmosphere by encouraging plankton growth, which captures carbon and sinks it deep towards the ocean floor1.

If successfully scaled up, such 'iron fertilization' of the sea could make a real dent in the high level of carbon dioxide in the atmosphere, which is causing global warming. Some researchers estimate that using the technique in the Southern Ocean alone could absorb 15% of carbon dioxide build-up. But ecologists caution that the technique could damage marine ecosystems in ways yet to be established2.

http://www.bioedonline.org/news/news.cfm?art=921

Six mesoscale (open ocean) iron fertilization experiments have been conduct over the last decade.

None have produced a significant enhanced flux of particulate carbon from the surface ocean to the deep ocean (i.e., they did not enhance the "biological pump" and did not sequester atmospheric CO2).

The growth of heterotrophic bacteria is also stimulated by iron additions (and by the increased availability of organic carbon in the Fe-stimulated phytoplankton bloom). They (along with protists and zooplankton) rapidly respire any newly formed organic carbon back to CO2.

Finally, there are real concerns about the Fe eutrophication of large areas of the ocean. The American Society of Limnology and Oceanography has lobbied against these schemes...

It was hoping that might be a last-resort option (While it would doubtless damage marine ecosystems, at this rate we'll have nothing left to damage).

Hey ho.

Heterotrophic bacteria outcompete phytoplankton for iron - in fact they are the first group of organisms to respond to iron enrichment (they crank up their growth and respiration within hours compared to nearly a week for diatoms).

And, to get the large fast-sinking phytoplankton to grow, you need repeated additions of iron.

If the additions are not done correctly, you could potentially stimulate bacterioplankton respiration and not stimulate photosynthesis at all - and get a small burst of CO2 released to the atmosphere.

Even if you successfully stimulated the biological pump with Fe, remineralization of that organic material in the ocean's interior would induce severe hypoxia and stimulate the production of methane and nitrous oxide (both powerful greenhouse gases). These gases would eventually be released to the atmosphere.

And finally, even if you successfully Fe-enriched the entire Southern Ocean and drew down all the nitrate and phosphate, it would reduce atmospheric CO2 by ~8%.

It looks like I'll been two and a half billion metric tons short.

I guess I'll have to stick to methane digesters at sewage plants.

The world is now putting out about 27 billion metric tons of carbon dioxide a year.