1. Lecture 13 Export Production Lecture 12 summary: Primary Productivity is limited mostly by nutrients. In low latitudes (< 45 o ), the limiting nutrient is most often NO 3. In high latitudes, iron (Fe) plays an important role.

2. Net Primary Production How much of this organic matter production sinks to the deep ocean?

3. CO 2 C org Phytopl. Zoopl. Bacteria Respiration (Heterotrophic) Photosynthesis “Net Primary Production (NPP)” RhRh NPP Export Production  From NPP to Export Production Define the f-ratio. What happens to export (  ) if primary productivity (NPP) goes up?

4. Export and sinking v Low nutrient areas favor small plankton due to surface area/volume consideration. High nutrient areas favor large plankton, rapid sinking rates, due to force balance (gravity=friction). The influences of plankton size lead to the following conclusion: Areas of high nutrients can support larger plankton, and a faster sinking of organic matter to the deep ocean.

5. Diatoms Large cells Fast growing Require high nutrients Require Silicate Surface Nitrate Region of high relative abundance

6. Prochlorococcus Synechococcus Picoplankton Extremely small Autotrophic Regions of high relative abundance.

7. Respiration and Temperature Like phytoplankton, heterotrophs (zooplankton and bacteria) are also sensitive to temperature. In warm waters, their rates of respiration (Rh) go way up (this is why we put food in the fridge!). As a result, warmer waters should be more efficient at recycling resources, rather than exporting them. Nitrosomonas

8. Nutrient Recycling Fast sinkingSlow Heterotrophs Large phytoplankton High nutrients High NPP 1) High export/low recycling regime and/or ZooplanktonBacteria Cool Temperatures Heterotrophs very sensitive to temperature Drag vs. Size Area/Volume Nutrient limitation

9. Nutrient Recycling Slow sinkingFast Heterotrophs Small phytoplankton Low nutrients Low NPP 2) High recycling/low export regime and/or ZooplanktonBacteria Warm Temperatures Heterotrophs very sensitive to temperature Drag vs. Size Area/Volume Nutrient limitation

10. Particle Export Ratio (“f-ratio”) Empirically derived effect of temperature and Net Primary Productivity on the f-ratio (the fraction of productivity that gets exported), and approximate values for some large ocean regions. 0.1 1.0 10 100 Subtropical Gyres Equatorial North Atlantic Southern Ocean Coastal

11. The Particle Export Ratio Identify regions for each bubble in previous plot.

12. Export Production The figure is the product of which two previous maps?

13. Coccolithophores Emiliani Huxleyi Produce CaCO 3 shells Can tolerate low light levels Size 1-40 μ m (microplankton) Region of high abundance

14. Diazotrophs Can fix nitrogen Trichodesmium Region of high abundance. Why?