Iron, which occurs in trace amounts in the oceans, is a limiting element for phytoplankton growth – this is old news. In the early 1990s, the oceanographer John Martin (then at Moss Landing Marine Labs) said “Give me a half tanker of iron and I’ll give you an ice age”, leading to the idea that we might be able to enhance carbon sequestration via the biological pump – the draw-down of carbon in the form of CO2 by growing phytoplankton.
Over the last twenty years, various groups have conducted iron fertilization experiments in different areas of the ocean. However, after big discussions and a lot of sniggering, the idea slowly seemed to retreat into the background, and the oceanographic mainstream lost interest for a while. Now – with an increasing sense of the threat posed by climate change felt by politicians and the public alike – the idea is back, and the concept, as well as its implications, are being discussed heavily in the scientific literature. By the way: if you look, please take the heavily biased wikipedia article with a grain of salt. You can also knock yourselves out with this collection of early iron fertilization references.
Of course it’s never as simple as all that: according to Mak Saito from Woods Hole Oceanographic Institution, Vitamin B12 is needed by phytoplankton as well, to pick just one example of many. But, just for fun, let’s imagine that iron was indeed all that’s needed.
Companies are ready to take advantage of the growing sense of urgency, offering to dump iron in exchange for CO2 credits – a recent January 2009 special in The Economist mentioning it attests to the real economic interest in this (by the way, I highly recommend this special, which provides a very good general overview of today’s threats to the oceans). Not least because of several companies being poised in the slots the International Maritime Organization, via the London Convention, is taking actions that may make it difficult to make any profit from the situation.
The Alfred-Wegener-Institute in Bremerhaven, Germany, sent its icebreaker ‘Polarstern’ out three weeks ago to conduct another iron fertilization experiment in the Southern Ocean. The current project is a collaboration with the National Institute of Oceanography, India; also on board are scientists from nine other institutions in India, Europe and Chile. When the ship left from Capetown, South Africa, on 7 of January, there were protests around the world, AWI director Dr. Karin Lochte found herself having to defend the project, and the AWI dedicated a website to explaining the backround and scientific aims of the project. After receiving the final go-ahead from the German Federal Ministry for Research, the Polarstern is now fertilizing.
So that is where it gets interesting. Not long after the Polarstern will have completed its fertilization experiment, a US expedition under the lead PI Dr. Ken Smith from the Monterey Bay Aquarium Research Institute is taking off to about the same area on the US Antarctic Program icebreaker ‘Nathaniel B. Palmer’ to study the effects of natural levels of iron released from melting icebergs. Ken Smith and his colleagues published their results from an earlier, exploratory cruise in late 2005 in a 2007 article in Science, and several blogs have posted nice write-ups of this.
In short, this is what happens: melting glaciers produce icebergs. As temperatures rise in the Antarctic – see the recent confirmation of a 50-year temperature record in Western Antarctica (we already knew about the Antarctic Peninsula) – more icebergs break off the glaciers, float away, and start melting and breaking up in quite a dramatic fashion. The release of trace elements from the iceberg leads to blooms in the surrounding water, which in turn support zooplankton, fish, and everything else up to birds and mammals.
So, the question is: will the US Antarctic Program cruise become part of the Polarstern experiment? I’ll be watching.
Finally, just for a giggle, I’d like to share this wonderful headline I found in the Daily Mail from 4 January with you: Amazing discovery of green algae which could save the world from global warming. The lead researcher, Professor Rob Raiswell from Leeds University, is quoted with having said ‘the earth itself seems to want to save us’ [by producing more icebergs that lead to blooms, which in turn draw CO2 from the atmosphere]. I am not sure the Daily Mail writer has checked the original paper in Geophysical Research Letters (which is available with Open Access, so no excuse). Rather, it seems to be solely based on the press release from Leeds University. Please make sure you don’t miss the figure caption in the Daily Mail piece: “British scientists have discovered that green algae could bury CO2 omissions at the bottom of the ocean”. Victor, if you’re reading this: I need a cartoon of a green alga in a superhero suit, complete with cape, digging a hole at the seafloor…
An Higgorant Question – could the release of iron from melting bergs be connected to Heinrich Events, associated with rapid climate change at the end of the last Ice Age?
Honest answer – I don’t know. But there are some people here at the ASLO meeting who probably have something to say on this, I’ll see whether I can catch them. If I had to guess based on what I know (which is a little, but not much), I’d think that if icebergs had anything to do with it, it wouldn’t have been icebergs alone but a range of factors working together (what’s new?).
It always amazes me how complex the system is – for example, other sources of natural ‘iron fertilization’ besides icebergs are islands (check out this paper published in some obscure little journal…), dust from desert storms that gets blown out over the sea, and runoff from land. It’s also not just iron that can cause blooms in the Southern Ocean, as I hinted at above – I talked to a lady from the British Antarctic Survey yesterday who found high abundances of diatoms in an area where iron concentrations did not seem favourable and hence responsible for the pattern she was seeing.
Update: article yesterday in Nature by Pollard et al. from Southampton on natural iron fertilization.
Henry, about your question.. I still can’t answer it – or rather, if I started, the answer would be very long – I think this might be another blog post. I still stand by my statement above after everything I heard today!
So what has been proved now? I read that it unfortunately had relatively little effect on reducing climate change gasses?
Hello, Global Changes. As to be expected with an enormous ecosystem like the oceans – in size as well as in ecological complexity – I don’t think anything has been ‘proven’. I am not an expert in this area, but I am happy to give you my opinion on it.
What seems to have become clearer is that adding iron to the ocean does not always lead to enormous blooms – it depends on what organisms are present in the first place: as mentioned briefly above, some may need substances other than iron alone to bloom, for example.
Another big outstanding question is how much carbon would or could actually get drawn out of the surface ocean (sequestration) into deeper layers – much of a short-term bloom may be recycled in the upper water column, which would obviously miss the point completely. (By the way: the question is not over with just drawing bloom material and thus carbon to the deep sea – the effects on deep-sea ecosystems has, to my knowledge, not even really been discussed yet).
Ironically, there is emerging experimental evidence that increasing sea temperatures may lead to both increased production and faster degradation of phytoplankton aggregates (think of algal dust bunnies). These aggregates are the main vehicle via which phytoplankton can sink into deeper layers. So, if the aggregates got degraded faster than they can sink down into deeper ocean layers, that would lead to the carbon remaining in the surface waters – but that’s another open question.
Other emerging problems are, for example, a possible link of iron availability and increased domoic acid (DA) production (DA is a neurotoxin responsible for certain forms of ‘shell fish poisoning’) by Pseudo-nitzschia, a very widely distributed algal genus which responds quickly to iron enrichment and which has recently been shown to produce DA in the open ocean (i.e. DA levels could increase in response to an iron-induced Pseudo-nitzschia bloom, which was previously thought not to be the case).
I don’t know whether my link on this post brought you here, but John Cullen’s slide show I posted there touches on a lot of these issues. He also sent me a link to other interesting talks given at an iron fertilization symposium held at Woods Hole in 2007, if you want more information and don’t feel like reading (if you do, I’d recommend this collection of articles, which I seem to have failed mentioning in my post).
Bottom line: we should be very sure (way more than at present – and maybe we can’t actually ever totally be) of the consequences before we even consider messing with earth’s biggest ecosystem.