1. Chemistry = Physics + Biology Regions where nutrients are found in surface waters are also areas of upwelling and/or deep mixing. (Aha!) But what prevents circulation from homogenizing nutrients everywhere? (Hmm…) But why doesn’t the biosphere remove all the nutrients everywhere? (Hmm…) It must be biological removal. (Aha!)

2. Lecture 10 Primary Productivity What factors influence the formation of organic matter in the surface ocean and its removal to depth?

3. CO 2 C org Phytopl. Zoopl. Bacteria Respiration (Heterotrophic) Photosynthesis “Net Primary Production (NPP)” RhRh NPP Export Production  Categorizing Plankton: 1) Trophic Status Some of the organic matter produced by autotrophs gets consumed by heterotrophs before it is removed from surface waters by sinking (or circulation).

4. Autotrophs: Phytoplankton Over 20,000 species in 8 phyla

5. Heterotrophs: Zooplankton

6. Bacteria Nitrosomonas Extremely abundant (10 28 )Oxidize NH 4 + to NO 3 -

7. Categorizing Plankton: 2) Chemical Function Some build shells: Some produce toxins: Some add nutrients: Some make (anti)greenhouse gases: The elemental ratios of “average” ocean plankton are very useful: But they don’t tell the whole story: Calcification Red Tides (HABs) Nitrogen fixation N 2 O, (DMS)

8. Coccolithophores Emiliani Huxleyi Produce CaCO 3 shells Can tolerate low light levels Size 1-40 microns (Prymnesiophyceae)

9. Dinoflagellates Specialized conditions, mostly coastal Can form a “Harmful Algal Bloom”, introducing toxins into water Relatively large: 100-2000 microns Capable of movement using flagella Trophic diversity (autotrophs, heterotrophs, mixotrophs) (Dinophyceae)

10. Diazotrophs Add nitrogen nutrients to the ecosystem Prokaryotes (no cell nucleus) Common in warm tropical waters Some endosymbiotic species (Cyanophyceae) Trichodesmium

11. Phaeocystis (Prymnesiophyceae) Implicated in the production of dimethyl sulfide (DMS) Form large muscillagenous blooms

12. Categorizing Plankton: 3) Size Why do we care about size? v a) Speed of a slowly falling sphere is proportional to its diameter squared (Stokes’ Law). b) Rate at which stuff can diffuse into particle per unit of volume is proportional to 1/diameter.

13. Prochlorococcus Synechococcus Most abundant autotroph on earth Discovered in 1988 Picoplankton Extremely small (~1  m) and difficult to observe Includes both Prokaryotes and Eukaryotes Ubiquitous but poorly characterized

14. Diatoms Relatively large (50-500 microns, but can be 2-2000 microns) Fast growing - Often the most numerous plankton in areas of high nutrient supply Require Silicon (Si(OH) 4 ) to build shell (“frustule”) Centric (pill-shaped) and Pennate (elongated) body shapes (Bacillariophyceae)