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Lecture 13 Export Production

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. Net Primary Production.

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Lecture 13 Export Production

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  1. Lecture 13 Export Production Lecture 12 summary: Primary Productivity is limited mostly by nutrients. In low latitudes (< 45o), the limiting nutrient is most often NO3. 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. From NPP to Export Production Photosynthesis “Net Primary Production (NPP)” Corg CO2 NPP Phytopl. Bacteria Zoopl. Rh Respiration (Heterotrophic) Define the f-ratio. What happens to export (p) if primary productivity (NPP) goes up? Export Production p

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

  7. Respiration and Temperature Nitrosomonas 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.

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

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

  10. Particle Export Ratio (“f-ratio”) 100 North Atlantic 10 Coastal Equatorial Southern Ocean 1.0 Subtropical Gyres 0.1 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.

  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 Produce CaCO3 shells Can tolerate low light levels Size 1-40 μm (microplankton) Emiliani Huxleyi Region of high abundance

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

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