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

2. 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

3. Global Nitrogen Cycle Annual Fluxes (Units are Mt N y-1)
N-Fixation:
Current estimates:
Recent estimates (1990’s): 10-20
Oceans 75000
Combustion 22
Rivers 43
Burial 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
(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

4. Klausmeier et al., Nature, 2004
The Redfield Ratio

5. 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.

6. 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?

7. 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?

8. 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

9. 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

10. 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

11. 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

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

13. 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