Ocean fertilisation Where the ocean meets the sky Ocean fertilisation is controversial, but it’s one of a number of geoengineering approaches to tackling climate change that politicians are starting to take seriously. So will it ever be worth the hassle, asks Hayley Birch

In January 2009, the Polarstern Germany, regards the whole affair large quantities of carbon through research vessel was treading water as a storm in teacup. ‘You could photosynthesis. This carbon would in the south Atlantic Ocean. The In short almost call it hysteria,’ he says. But be drawn down far below the surface icebreaker, laden with some of  Iron could fertilise his team’s plans were undeniably when the algae eventually died and the most sophisticated scientific large algal blooms in the controversial. In studies that, sank. Done on a large enough scale, instruments available aboard a ship, ocean to lock up CO2 according to some, would test the technique could offer a way to had carried its cargo of 48 scientists when it sinks international agreements under reduce the amount of carbon dioxide from Cape Town, South Africa, to a  Little is known of the United Nations’ Convention on in the atmosphere. remote destination around 2000km the potential impact Biodiversity (CBD), the researchers north of the Antarctic coast. A few on ocean ecosystems, were intending to carry out the Seeding the seas days before, the team had received making the idea quite largest experiment to date using a The team aboard the Polarstern was the frustrating news that, after controversial geoengineering technique known as eventually given the green light after four years of planning, the German  Political support is iron fertilisation. Their theory: that a positive review from the British government had called a halt to its building, but experiments phytoplankton (algae), thriving on a Antarctic Survey, Institute of Marine experiments just days before they are tightly controlled by diet of iron, would bloom and take up Research and German Federal were due to begin. international agreements The future of the mission was riding on the outcome of an independent review ordered by the science ministry in response to protests from environmental campaigners. If the project – which involved pouring a solution containing 10 tonnes of iron sulfate into the ocean – was deemed to be environmentally unsafe, the crew of the Polarstern would have no choice but to turn the vessel around and head back to port. The Polarstern crew Looking back, lead researcher had to wait until the last Victor Smetacek of the Alfred moment to find out if their

Wegener Institute in Bremerhaven, experiment was approved INSTITUTE WEGENER ALFRED 52 | Chemistry World | September 2011 www.chemistryworld.org HANNES GROBE HANNES

Environment Agency – under the fertilisation experiment ever carried Those field experiments of locating a suitable spot for iron CBD, small scale iron fertilisation out. Although no peer reviewed study that have been approved fertilisation. As Richard Lampitt, studies are allowed as long as they has yet been forthcoming, the results have met with varying an ocean fertilisation expert at the are first subjected to rigorous are already in the public domain. degrees of success National Oceanography Centre in assessment. And so, on 27th January Within two weeks of adding iron, Southampton, UK, explains, the 2009, the scientists proceeded with the concentration of chlorophyll Southern Ocean, surrounding the their plans to fertilise a 300km2 – the pigment enabling the algal Antarctic, ought to be the perfect patch of ocean, with modest success. cells to the harness the energy in place because it is abundant in Since then, the political sunlight – had doubled, indicating a nutrients. ‘There you just add the complexities surrounding iron substantial bloom. But the algae were iron and then the productivity will fertilisation studies have developed soon feasted upon by crustaceans, increase until it is limited by some somewhat. While a new assessment with the end result being a slight, but other nutrient,’ he says. ‘And it framework developed by the ultimately disappointing, increase in has been suggested that if you add International Maritime Organisation transport of carbon to the deep sea. iron to these regions, the oceans now governs what and how ocean The appetite of the local grazers in these areas will take up carbon fertilisation activities can be was surprising, but there is another dioxide from the atmosphere carried out, political interest in possible reason for the poor result. and pack it away for more than geoengineering is growing as pressure The type of phytoplankton inhabiting 100 years.’ In less frequently to ‘do something’ about climate this particular area of ocean relies studied low-nutrient areas, adding change intensifies. Sprinkling iron on silicon to build a key part of its iron causes blooms for another on the ocean might seem a relatively tough cell wall. So in the absence of reason – because nitrogen-fixing straightforward solution next to a an infinite supply of silicon, adding phytoplankton need iron to help solar sunshade – and, according to iron has only limited potential for them fix nitrogen from the air. Smetacek, could be our best option. enhancing growth. In an earlier study Location is crucial then, but ‘There is no other alternative, no in silicon-rich waters further south, ‘Sprinkling iron experiments would also have to other approach that could take out however, Smetacek says his team on the ocean is a be on a much larger scale than has more CO2,’ he argues. But no one observed substantial deep carbon so far been attempted in order to knows for sure what the long term transport after a large algal bloom. straightforward prove that the carbon sequestration consequences will be and, crucially, solution benefits would be worthwhile. All of whether they will be worth it. Location, location, location the studies so far – 13 by independent Smetacek’s study remains, The outcome of these experiments compared to a researchers and two by commercial marginally, the largest ocean illustrates the rather tricky problem solar sunshade’ companies – have focused on www.chemistryworld.org Chemistry World | September 2011 | 53 Ocean fertilisation

by ‘a lot of misguided and unhelpful publicity’, he says.

Pollution or solution? The media furore surrounding Smetacek’s 2009 experiment has afforded him some sympathy with Lampitt. ‘Iron fertilisation experiments have been given a bad name,’ he agrees. Those who oppose iron fertilisation often do so on the basis that it is pollution; dumping iron into the sea, with potentially catastrophic consequences for marine life. But Smetacek argues that his own experiments have only caused algal blooms of the same magnitude as natural blooms – a claim that is backed up by satellite imagery. Lampitt adds that the amount of iron floating around from volcanoes, rivers, dust storms and the like is many, many orders of magnitude

SCIENCE PHOTO LIBRARY PHOTO SCIENCE greater than the amount scientists are talking about adding artificially. small areas of ocean and lasted a ‘No,’ he says. ‘We haven’t secured Natural phytoplankton As regards the effects on marine matter of weeks. And despite the funding so far to do the fairly blooms can reach ecosystems, Phil Williamson from need for further research, the new large experiments, which are enormous sizes. the University of East Anglia in the assessment criteria now pose more very expensive.’ Meanwhile, Fertilisation aims to UK, one of the authors of a recent of a challenge to those planning the consortium is pushing for reproduce this to lock up report on iron fertilisation for the fertilisation experiments. Lampitt greater political recognition of useful amounts of CO2 Intergovernmental Oceanographic believes the criteria are a necessary the role iron fertilisation could Commission (IOC),1 is more and important part of a rigorous play in addressing climate philosophical. ‘It would produce process that scientists should have change. In June this year, ISIS changes to the ecosystems, yes. to go through before undertaking representatives joined a meeting Whether you consider those to large scale experiments. But they of the Intergovernmental Panel on be damage or not depends on... will most likely hamper his own Climate Change (IPCC) in Peru. human evaluation and perspective,’ organisation’s research, as one of The talks will feed into the IPCC’s he muses. Besides which, he says, 13 institutions that have recently fifth assessment report, due for many of the damaging effects that formed the In-Situ Iron Studies publication in 2012. According have been suggested (see ‘Facing (ISIS) consortium, of which Lampitt to Lampitt, politicians are finally the consequences’, below) – such as is co-chair. starting to take the idea of ocean decreasing oxygen levels in deeper So perhaps ISIS has larger fertilisation seriously – but it’s been water, with potential impacts on scale projects in the pipeline? a battle to undo the damage caused biodiversity – are little more than speculation. Without further studies, however, there can be no Facing the consequences hard evidence. Concerns have been raised over the possible The IOC-commissioned report unintended consequences of ocean fertilisation: concludes that ‘it is not yet known  Phytoplankton growth could produce climate- how iron-based ocean fertilisation relevant gases, such as dimethyl sulfide. Impact of might affect zooplankton, fish and trace gases on ozone levels may also be important seafloor biota’. Equally though, it is not yet known how much  Some studies have observed changes to the relative carbon could be sequestered by the abundance of different phytoplankton species, with approach, and how long it would stay unknown impacts on food webs out of the atmosphere.  Blooms could rob the ocean of other nutrients (like Keeping carbon down nitrate or phosphate), potentially reducing the According to Williamson, productivity of surrounding waters fertilisation ‘won’t make a massive  Decomposition of sunken blooms could deplete difference’. The IPCC estimates dissolved oxygen stores, which are essential for that the net uptake of carbon by the marine life, and produce greenhouse gases more oceans is just over 2 billion tonnes potent than CO2, offsetting any carbon benefit per year, equivalent to 6 tonnes of carbon to every square kilometre of  Carbonate shells dissolve in acid. Sequestering ocean. But by 2100, under a ‘business large amounts of CO2 could acidify the deep as usual’ scenario, each person on ocean, affecting the habitats available to shell- the planet is expected to be adding building species SCIENCE PHOTO LIBRARY PHOTO SCIENCE to the atmosphere another 6 tonnes 54 | Chemistry World | September 2011 www.chemistryworld.org ‘And the oceans are going to take this CO2 up anyway over the course of thousands of years – it dissolves in surface water and then that surface water will sink and transfer the carbon to the deep ocean. And in the meantime, the surface ocean is being acidified. Whereas what we are doing is diverting the carbon directly to the deep ocean where it will be completely lost.’ But will it? The big question is: how long can we keep the sequestered carbon down? Will it stay there for ever or will it leak slowly back into the atmosphere? This is a question that can only be answered by modelling. Anand Gnanadesikan and colleagues at Princeton University in New Jersey, US, have predicted that anywhere between 2 and 44 per cent of the carbon delivered to the deep ocean by fertilisation could be returned to the atmosphere within a century, with verification of the real proportion proving nigh on impossible.2 This verification issue is one of the reasons that private companies interested

NOAA in iron fertilisation have had trouble arguing they should be eligible for of carbon per year (the same as Phytoplankton absorb estimates suggest fertilisation could carbon credits. the current European average). In CO2, but locking up that get rid of one out of the eight billion theory, it could be possible, says carbon depends on the tonnes of carbon that human activity A worthwhile struggle Williamson, to double ocean uptake dead plankton sinking to is belching into the atmosphere So now that commercial interest of carbon by iron fertilisation. The the deep ocean each year – if this was the case, he has withered, it’s left to academic trouble is, that would only solve says, its contribution would not institutes and networks like ISIS to around 5 per cent of the problem be trivial. Smetacek, on the other lead the way. But in light of the media that we face in the future, since there hand, sees more potential in iron bashings, epic voyages to distant are around 20 people per square fertilisation than in other carbon parts of the ocean and questionable kilometre of ocean. sequestration approaches, such as climate benefits, isn’t it all a lot of Lampitt agrees iron fertilisation forestation. The amount of carbon effort for precious little reward? is no silver bullet; rather it’s one of that needs to be sequestered is equal Smetacek doesn’t think so. He says a stable of different geoengineering to one third of terrestrial vegetation. ocean fertilisation studies will approaches that could contribute That amount is virtually impossible teach us more than just whether something to climate change to store on land, Smetacek argues. we can fix our broken climate with mitigation. The most optimistic ‘There’s no scope for it,’ he says. iron. ‘There’s no basic science that is useless if it’s good science, Iron recycling by whale poo if it increases your understanding of what you’re studying,’ he says. An interesting aside to the ‘And it’s the same with these iron fertilisation debate is iron fertilisation experiments. that carbon cycling can also We’re learning about how pelagic take place through natural ecosystems – the plankton – how ‘fertilisation’ activities – some of they function. And we don’t even which we are only just beginning know the basics yet.’ to understand. In 2010, Trish Lavery at Flinders University Hayley Birch is a freelance science in Adelaide, Australia, and writer and editor based in Bristol, UK colleagues calculated that the iron-rich faeces of sperm References and further reading: whales could be responsible 1 D Wallace et al, Ocean fertilization: A scientific summary for policy makers, 2010 SCIENCE PHOTO LIBRARY PHOTO SCIENCE for as many as 400 000 tonnes (IOC/BRO/2010/2) of carbon being transported Sperm whales are natural ocean fertilisers 2 A Gnanadesikan et al, Global Biogeochem. to the ocean floor each year Cycles, 2003, 17, 1050 (although they put half of this enabled by data from artificially increase our understanding of (DOI: 10.1029/2002GB001940) back into the atmosphere seeded blooms. Thus, one the nutrient cycling processes 3 T J Lavery et al, Proc. R. Soc. B., 2010, 277, through respiration).3 1699 (DOI: 10.1098/rspb.2010.0863) The argument in favour of iron that are important in marine 4 V Smetacek and S W A Naqvi, Phil. Trans. team’s calculations were fertilisation studies is that they ecosystems. R. Soc. A, 2008, 366, 3947 (DOI: 10.1098/ rsta.2008.0144) www.chemistryworld.org Chemistry World | September 2011 | 55