1. The influence of dust on ocean biogeochemistry; chasing Saharan dust storms Eric Achterberg, Micha Rijkenberg, Polly Hill, Matt Patey, Maria Nielsdottir, Mark Stinchcombe, Jane Heywood, Duncan Purdie, Mike Zubkov, Peter Statham National Oceanography Centre Southampton Claire Powell, Tim Jickells and Alex Baker University of East Anglia Manuel Dall’osto and Roy Harrison University of Birmingham Ellie Highwood University of Reading

2. Overview Atmospheric inputs into the ocean Poseidon 332 cruise Jan-Feb 2006 Discovery 3xx cruise Jan-Feb 2008

3. Dust Inputs to the Oceans Tg (10 12 ) yr -1 Global Dust Production1700 Dust Inputs To The Oceans442 Iron Inputs To The Oceans 15.5 Soluble Iron Inputs To The Oceans0.15 (1% solubility)

4. N. Atlantic receives largest global dust load Proximity to Sahara Modelled dust deposition, Tegen et al. 2005 The North Atlantic: high dust inputs

5. AMT 15 Transect Southampton, UK - Capetown, S. Africa, September October 2004 (Upwelling Data Excluded)

6. Sarthou, Achterberg et al., Deep Sea Res. 2003 Polarstern Anreise cruise 2000

7. (ii) Hydrocast section data Dissolved iron (AMT 15) Ussher, Achterberg, Worsfold, in prep.

8. Surface water (1000 m) dissolved iron and aluminium (nmol/kg) in the Atlantic along CLIVAR A16 (2003; Chris Measures and Bill Landing)

9. Main hypothesis of our UK SOLAS project: Atmospheric inputs control rates of primary production and microbial diversity in oceanic waters where nutrients are limiting

10. Poseidon Cruise POS 332 January 28 – February 23 2006 Objectives of cruise: 1. Provide improved estimate of dust inputs to tropical N Atlantic 2. Determine influence of dust on species diversity, nutrient cycling and N 2 fixation FS Poseidon

11. MODIS tau-869 Aerosol opt. depth

12. Surface water dissolved aluminium nM

13. Surface water dissolved Fe

14. Surface water dissolved free organic Fe binding ligands nM Rijkenberg et al., 2007 Submitted to Marine Chemistry

15. Conditional stability constants of Fe binding ligands in surface water Open circles: south of Cape Verde Closed circles: north and east of Cape Verde

16. CTD FRRF profile for Cape Verde region (typical for cruise)

17. Nitrogen fixation in the Cape Verde region

18. MODIS tau-869 Aerosol opt. depth 3 Feb. 14:25 (supplied by Steve Groom et al. PML)

19. MODIS tau-869 Aerosol opt. depth 4 Feb. 15:10

20. High volume aerosol filter for February 4, 2006 Claire Powell, UEA

21. Saharan dust Cape Verde dust Dust particles detected during cruise using ATOFMS

22. Cruise track 1 2 3

23. Surface water dissolved Fe n = 16n = 17 nM

24. Surface water dissolved free organic Fe binding ligands n = 4n = 3 nM Rijkenberg et al., 2007 Submitted to Marine Chemistry

25. Surface water microbial community Prochlorococcus Transect dates Feb 3-4Feb 10Feb 11 Cells/ml 0.0 5.0e+4 1.0e+5 1.5e+5 2.0e+5 2.5e+5 n = 14n = 7 n = 8 Synechococcus Feb 3-4Feb 10Feb 11 Cells/ml 0 20000 40000 60000 80000 n = 14n = 7n = 8 Picoeukaryotes Feb 3-4Feb 10Feb 11 Cells/ml 0 1000 2000 3000 4000 5000 6000 n = 14n = 7n = 8 Transect dates

26. Discovery 314 Cruise 2007 Cancelled due to problems with vessel

27. Discovery 326 Cruise 2008 Study spatial-temporal variability in atmospheric dust inputs and phytoplankton- bacterial responses Cruise Plan Region: transect west of the N Africa into oligotrophic waters  looking for dust storms Cruise track will be guided by satellite observations of dust Period: 32 days-January 5-February 5

28. Discovery 326 Cruise 2008 Measurements and experiments: -Dissolved and particulate Fe, Al, Mn analyses -Nanomolar and micromolar nutrients analysis -Microbiology (flow cytometry; FISH; labelled amino acid uptake) -Nitrogen fixation measurements, with NIFH gene determination -DMS measurements and UV exposure studies -Water column light measurements -Rain and high volume dust collection for subsequent land-based analysis -Real-time ATOFMS measurements of aerosol particles -Low volume dust collection with ship-board dissolution experiments (Bill Landing CLIVAR approach) -Bottle dust dissolution experiments with subsequent dissolved Fe/Al, nutrient measurements -Studies of effect of leached dust solutions on microbial communities -Nutrient addition bioassay experiments (incl. dust additions)

29. Acknowledgements Captain and crew of FS Poseidon NERC-UK-SOLAS for funding the research Post-doctoral position available at NOCS on Fe biogeochemistry in Iceland-Irminger Basins