Scientific aims and description of LOHAFEX: An Indo-German iron fertilization experiment (January March 2009) in the Southern Ocean

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1 Scientific aims and description of LOHAFEX: An Indo-German iron fertilization experiment (January March 2009) in the Southern Ocean The Alfred Wegener Institute for Polar and Marine Research (AWI), Germany, and the National Institute of Oceanography (NIO), India, are jointly conducting an iron fertilization experiment from 7 January 17 March 2009 in the Southwest Atlantic Sector of the Southern Ocean on board the German research vessel Polarstern in order to test a range of scientific hypotheses pertaining to the structure and functioning of Southern Ocean ecosystems and their potential impact on global cycles of biogenic elements. The experiment LOHAFEX, (Loha is the Hindi word for iron, Fertilization EXperiment) is part of the Memorandum of Understanding between the two Institutes signed by the heads of their respective parent organisations, the Helmholtz Association, Germany and the CSIR, India, in the presence of the Chancellor of the Federal Republic of Germany and the Prime Minister of India on the 30 th October The cruise led by Prof. Victor Smetacek (AWI) and Dr. Wajih Naqvi (NIO) will devote at least 45 days to the experiment, by far the longest period of on-site surveillance of any iron fertilized phytoplankton bloom. In view of the ongoing controversy regarding future ocean iron fertilization activities we stress here the need to distinguish legitimate, inter-disciplinary scientific experiments such as ours carried out by respected research institutions, from publicity-stunt attempts at commercialising iron fertilization for the carbon credit market. It was this latter attempt in the summer of 2007 that received much media attention and which led to the spate of critical comments on ocean iron fertilization activities. In the following we provide a brief background on the history of iron fertilization experiments and their impact on scientific understanding of the oceans. The technique of artificial iron fertilization and what it achieves in iron-limited oceans is presented in the light of its environmental impact. Next, we describe the aims of LOHAFEX, the rationale for site selection and a list of the processes relevant to various branches of ocean sciences that will be measured during the experiment. We append more detailed, published information on each of these topics, including a call to continue scientific experiments by a group of leading scientists published in Science this year. Also appended are the recommendations on ocean fertilization of the London Convention Treaty on ocean dumping made at its meeting in October 2008 which specifically allow scientific experiments such as ours. Ocean iron fertilization (OIF) experiments Scientific experiments based on this technique are equivalent to the classic perturbation experiments routinely employed by all branches of science to analyse the workings of complex systems. A dozen OIF experiments have been carried out since 1993 by scientists from a number of countries that have proven the technique to be a powerful method to study and quantify ecological and biogeochemical processes in the ocean. This data is needed to test scientific hypotheses pertaining to the structure and functioning of oceanic ecosystems in order to further our understanding of the links between earth s climate and the biosphere - in the current ocean and through geological time scales - and to parameterise models required to predict future climate scenarios. Not surprisingly, the results of most experiments as well as several climate models incorporating OIF have been published in high profile journals such as Nature and Science. OIF is very much a part of mainstream, modern oceanography and hence inter-disciplinary earth system science.

2 Currently the major focus of OIF experiments has been the biological carbon pump: the rain of particles sinking from the surface layer to the deep ocean and sea floor which transports carbon from the atmosphere to the ocean interior where it is sequestered for time scales of decades to centuries depending on the intensity of the particle rain. However, these experiments also yield a wealth of insights into the structure and functioning of planktonic and benthic ecosystems in terms of biodiversity, genomics, evolutionary ecology and are hence of interest to a broad field of biological sciences. These aspects have been barely addressed by previous experiments because of the limited personnel capacity on board most research ships. Artificial iron fertilisation is carried out by releasing a solution of ferrous sulphate (the same substance used to treat patients suffering anaemia) in the ship s propeller wash along a track about 2 km apart over an area depending on the hydrodynamics of the region and the intended duration of the experiment. Short-term experiments (1-2 weeks) in calm, warm seas need be only a few tens of km 2 in area, longer-term experiments in stormy seas such as the Southern Ocean (5-7 weeks) will have to fertilize a few 100 km 2. The iron concentrations reached within the fertilized patch after lateral homogenization are equivalent to those recorded from natural iron fertilization caused by dust settling from the atmosphere, contact with continental and island margins and from melting ice bergs. Therefore, the densities of experimental phytoplankton blooms are in the same range as those attained by natural blooms. However, because of lateral mixing, the patch increases in size over time which results in dilution of the experimental water with unfertilized water. Hence the effects of dilution in the centre of the patch will decline with its size. Longer-term experiments studying bloom development, its fate and effect on the deep ocean and underlying sediments will have to be much larger than the first generation of experiments. Adding iron to iron-limited ocean waters has the same effect as watering a parched landscape. Plants, in this case the unicellular algae of the phytoplankton, increase their growth rates whereby the same species of phytoplankton are stimulated by iron addition as commonly occur in natural blooms in the region. Their growth results in stimulation of other components of oceanic ecosystems including zooplankton and bacteria. The amount of carbon eventually sequestered in the deep ocean by the biological pump depends on how much algal biomass is recycled in the surface layer by zooplankton and bacteria and how much sinks to depth. Previous experiments have not been able to adequately record this phase of the bloom because they have been too short or otherwise restricted. However, they have all demonstrated that OIF experiments simulate natural processes and that their environmental impact is hence benign. Scientific aims of LOHAFEX LOHAFEX will be the sixth OIF experiment conducted in the Southern Ocean and the third experiment carried out from RV Polarstern. In contrast to all previous experiments, LOHAFEX will be located in a productive region influenced by coastal waters. We have found that placing the fertilized patch in the closed core of a meso-scale, stable eddy identified from satellite images enables one to track particles sinking out from the surface layer through the deep water column to the underlying sediments. The aim of LOHAFEX is to test the hypothesis that iron fertilization of this ecosystem will promote rapid growth of coastal diatom species which will have a significant effect on the magnitude and composition of vertical flux to the deep sea and underlying sediments. Since coastal diatoms have higher growth rates and thinner shells than oceanic species, the effect on the pelagic food web and on carbon to silicon ratios in the water column, including material subsequently deposited on the sea floor, will differ accordingly. The results will be of great significance for interpretation of

3 sediment proxies used to ascertain productivity regimes of the Southern Ocean during past glacial-interglacial climate cycles. Brief description of the experiment Because we intend investigating the fate of the fertilized bloom over its entire duration over a month and a half we will need to fertilize a larger patch than in previous, shorter experiments. A circle of 10 km radius (300 km 2 ) will be fertilized twice with 20 tonnes of dissolved ferrous sulphate (Fe SO 4 ) acidified with HCl to yield a concentration of about 2 nmol Fe L -1 which is still well below iron concentrations commonly measured in coastal waters. The Fe SO 4 we will use is sold in gardening shops to improve lawns and employed by sewage treatment plants to remove phosphate, so is free of toxic contaminants. We expect that fertilization will result in growth of a diatom bloom comprising species of very different shape, behaviour and hence impact on the ecosystem and the depth to which carbon fixed by it sinks. The bloom will stimulate grazing by zooplankton and bacterial activity. After about 3-4 weeks, some species of phytoplankton will stop growth whereas others will continue. At this stage, some algae will form aggregates and commence sinking out of the surface layer. We will follow these sinking particles through the deep water column during the demise phase of the bloom. The composition of the particles and the effect of zooplankton grazing and bacterial activity on their formation and fate will also be investigated. The effect of the bloom on concentrations of oxygen and various climaterelevant trace gases will be monitored in the surface and the deep water column. The effect on the biota of the underlying sediments will also be addressed. The data will subsequently be used to parameterise mathematical models on growth and fate of phytoplankton blooms, their environmental impact and their potential role in sequestering carbon in the deep ocean. The team of 48 physical, chemical, geochemical and biological oceanographers on board will study the following processes: 1) patch dynamics in the surface layer and its effect on the underlying deep water column and sediments 2) uptake of dissolved biogenic elements (C, N, P, Si, Fe) and incorporation into particulate pools 3) production of trace gases including CH 4, N 2 O, DMS and halogenated hydrocarbons 4) primary production by phytoplankton, bacterial production and grazing by protozoo- and metazooplankton 5) species composition and changes in the assemblages of phytoplankton, bacteria, protozooplankton and metazooplankton 6) vertical flux of particles from the surface with neutrally buoyant sediment traps, profiling camera systems and 234 Thorium 7) composition of fluff on the sediment surface. The effects of increasing productivity on selective grazing and breeding of zooplankton will also be studied. The shrimp-like krill, which is the main food of Antarctic penguins, seals and whales, is likely to be present in the experimental region. Stocks of krill have declined by over 80% during the past decades and their response to the iron-fertilized bloom will indicate whether the decline is due to declining productivity of the region for which there is evidence. Thus, iron fertilization of the krill habitat could well help in halting this alarming decline and possibly even boosting their stocks to their former high densities which will facilitate recovery of the decimated great whale populations. Details on the scientific rationale, investigations to be carried out and the names of the participating scientists are available on the web site of the NIO, Goa.

4 Institutions participating in LOHAFEX: Germany Alfred-Wegener-Institut für Polar- und Meeresforschung in der Helmholtz-Gemeinschaft Postfach Bremerhaven Max Planck Institute for Marine Microbiology Celsiusstrasse 1 D Bremen India National Institute of Oceanography Dona Paula , Goa Centre for Cellular and Molecular Biology Uppal Road, Hyderabad National Engineering Research Institute Nehru Marg, Nagpur Physical Research Laboratory, Navrangpura, Ahmedabad Italy Stazione Zoologica Anton Dohrn Villa Comunale Napoli Spain Mediterranean Institute for Advanced Studies (IMEDEA) C/ Miquel Marquès, Esporles, Mallorca Illes Balears Chile Universidad Austral de Chile Independencia 641 Valdivia UK National Oceanography Centre, Southampton (NOCS) University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH France Laboratoire d'oceanologie de Villefranche Université Pierre et Marie Curie, Paris

5 Station Zoologique, Chemin du Lazaret, Villefranche sur mer Documents accompanying this package: 1) Paper by Smetacek & Naqvi (2008, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences /rsta ) providing the scientific background for OIF 2) Scientist Statement in Science (Buesseler et al 2008)