Pick one idea out of all this? The Domain of SOLAS Research Pick one idea out of all this?

SOLAS Mid-Term Strategic Planning (underway) Coordinated, Cross-Cutting Issues suited to Coordinated International Research Surface ocean nutrient limitation / cycling Atmospheric deposition / dust effects on marine ecosystems Air-sea gas fluxes at Eastern boundary upwelling systems Sea ice as a habitat, reaction surface and barrier Marine aerosol formation Ship plumes Large scale experiments for hypothesis testing

Global Nitrogen Cycle Annual Fluxes (Units are Mt N y-1) N-Fixation: Current estimates: 100-200 Recent estimates (1990’s): 10-20 Oceans 75000 Combustion 22 Rivers 43 Burial 10 - 40 95 140 <250 Denitrification N2-Fixation Lightning 3 Biomass 1200 Fixation 151 160 Haber-Bosch Process 93 Atmosphere 4.0 x 109 Sedimentary Rocks 1 x 109 Combustion 50-80 Atmospheric N deposition 60-70 (Duce et al., Science, 2007) NH3 emission 60-120 Oceans 8 x 105 Wenn Titel zweizeilig: Vertikal 1,4cm Annual Fluxes (Units are Mt N y-1) Reservoirs in Mt N

Klausmeier et al., Nature, 2004 The Redfield Ratio

Arrigo, Nature, 2005: The key conclusion….. is that the canonical Redfield N:P ratio of 16 for phytoplankton is not a universally optimal value but instead represents an average for a diverse oceanic phytoplankton assemblage growing under a variety of different conditions and employing a range of growth strategies…. Consequently, the deep-sea NO3:PO4 ratio of ~16:1 simply reflects the stoichiometry of the current global phytoplankton community. …..the old notion of a single nutrient (or other resource such as light) limiting the growth of marine phytoplankton must give way to a more complex view that allows for limitation by multiple nutrients, both at the level of the individual cell and at the level of the entire community.

Nitrogen-fixation as an example: Currently open questions: Where does N-fixation occur in the ocean? How much? Who does it? When / how do they do it? What controls / limits it? Feedbacks? Biogeochemical questions: Where? How much? What is the control? How tight are the feedbacks?

A remote-sensing perspective… Westberry and Siegel, 2006 ARE THE REMOTE SENSING ALGORITHMS RELIABLE? Excess NO3- highest in North Atlantic….indicator of N-fixation? A classical preformed nutrient perspective… OR IS THIS A REFLECTION OF FIXED-N REMOVAL ELSEWHERE?

N-fixation tightly coupled to excess P Where does N-fixation occur? And what controls it? (a modelling perspective….) N-fixation tightly coupled to excess P Calculations based on model-based convergence of excess P, or P*.. Likely dependent on model-based representation of circulation, upwelling and production Deutsch et al., Nature, 2007

nmol N l-1 h-1 Mills et al., Nature, 2004 An experimental perspective… ADD NUTRIENTS TO SURFACE SEAWATER INCUBATE ON-DECK FOR 48 HOURS nmol N l-1 h-1 At least 10 treatments per experiments. The concentrations of nutrients added were very small. N was given as ammonium nitrate because of the pico that doesn’t take up NO3 Saharan dust was characterized chemically we know the percentage of P,Fe and there is very little nitrogen Also know the dissolution of both Fe and P Mills et al., Nature, 2004

A geographical survey perspective… Surface N2 fixation Integrated N2 fixation (fractionated) Trichodesmium counts Dissolved Al: tracer for dust input Dissolved Fe Moore et al., submitted

N-fixation NOT coupled to excess P Surface N2 fixation DIN and DIP N-fixation NOT coupled to excess P P*, DOP*, TDP* Slide of girls in swimming pool N* in the nutricline -40 40

Data from Langlois et al. 2008 A molecular perspective: Latitudinal distribution (and diversity) of diazotrophs Data from Langlois et al. 2008

Surface Ocean Nutrient Limitation and Cycling Strategy to address: Surface Ocean Nutrient Limitation and Cycling Coordinate and combine the different perspectives (modelling, molecular, survey, experiments, remote sensing). scientific progress is being made; new approaches are available major breakthroughs are possible SOLAS needs to accelerate and enable progress Some specific activities: Surface ocean surveys. Make better use of long research vessel transits… Explore use of Volunteer Observing Ships. (Cooperate with shipping industry) Sustain and make use of Time-series Sites Design appropriate large-scale experiments for hypothesis testing