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Suggestions for getting an A

Suggestions for getting an A. How to deal with equations? Don’t panic! If you understand an equation, you can understand the process it describes Why so many graphs? Teach you how to read (and draw) different kinds of graphs Illustrate principals and processes

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Suggestions for getting an A

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  1. Suggestions for getting an A • How to deal with equations? • Don’t panic! • If you understand an equation, you can understand the process it describes • Why so many graphs? • Teach you how to read (and draw) different kinds of graphs • Illustrate principals and processes • When in doubt, think about what’s happening with the physics.

  2. Suggestions for getting an A • How to deal with equations? • Don’t panic! • If you understand an equation, you can understand the process it describes • Why so many graphs? • Teach you how to read (and draw) different kinds of graphs • Illustrate principals and processes • When in doubt, think about what’s happening with the physics.

  3. Passed with a C or better

  4. Texting, Facebook, video games

  5. Suggestions for getting an A • How to deal with equations? • Don’t freak out • If you understand an equation, you can understand the process it describes • Why so many graphs? • Teach you how to read (and draw) different kinds of graphs • Illustrate principals and processes • When in doubt, think about what’s happening with the physics.

  6. An informal survey…

  7. Biology of mixed layer • Primary production by Phytoplankton - small drifting organisms that photosynthesize • Competition and limits on production • Critical and compensation depths

  8. Photosynthesis (P) Carbon dioxide (C,O) + Water (H,O) + Nutrients (N,P) + Light energy Oxygen (O) + Organic matter (C,H,O,N,P) Requires chloroplasts Plants, algae proteins fats carbohydrates nucleic acids

  9. Respiration (R) Carbon dioxide (C,O) + Water (H,O) + Nutrients (N,P) Oxygen (O) + Organic matter (C,H,O,N,P) Every living thing respires proteins fats carbohydrates nucleic acids

  10. Primary Production - Definitions Gross Primary Production (GPP) = rate of carbon fixation by photosynthesis units = [Mass / Area / Time], e.g. [g C m-2 y-1] Respiration (R) = rate of carbon (CO2) loss through metabolism Net Primary Production (NPP) = GPP - R Need GPP>R for net growth!

  11. Production ≠ Biomass • Production is a rate e.g. [g C m-2 y-1] • Biomass is a concentration e.g. [g C m-2]

  12. “Paradox of the Plankton”There are many species of phytoplankton, despite few limiting resources and lots of mixing. Phytoplankton (single-celled primary producers) have various competitive strategies that enable coexistence.

  13. Four major players • Small (<1 m) or • Large (0.5-4 mm) • Nitrogen fixers • Large (2-200 m) • Have silica frustules • Small (2-25 m) • Have CaCO3 tests • Large (5-2000 m) • Have unique life • cycle & blooms

  14. What limits production? • Nutrients • Light • Intensity • Spectrum • Temperature • Grazing by zooplankton

  15. The environment varies in space and time. Different phytoplankton grow well under different conditions. Light Intensity Low High Narrow Broad Light Spectrum Low High Temperature High Low Nutrients Deep water / Winter Shallow water / Summer

  16. Nutrients • N, P, Si, Fe • Nitrogen is most often limiting in ocean • Bioavailable forms of inorganic N: • Nitrate (NO3-) • Ammonium (NH4+) • Nitrite (NO2-)

  17. At low nutrient concentrations, smaller phytoplankton tend to grow faster r r Assume cell is a sphere. Surface area: Volume: Surface area to volume ratio: Smaller cells have relatively more surface area for taking up nutrients.

  18. Growth rate varies with [nutrient]  = Specific growth rate (d-1) Curve “saturates” N = [Nutrient]

  19. Growth rate varies with [nutrient] max max/2 Ks  = Specific growth rate (d-1) Michaelis-Menten Kinetics “half-saturation constant” N = [Nutrient]

  20. Different strategies of nutrient use • Coccolithophores • Low max • Low Ks • Diatoms • High max • High Ks High or variable nutrients High mixing, upwelling Low average irradiance High turbulence Chronically low nutrients Stratified conditions High average irradiance Low turbulence

  21. Larger plankton (diatoms and dinoflagellates) most adapted to high-nutrient conditions. Light Intensity / Irradiance Low High Narrow Broad Light Spectrum Low High Temperature High Low Nutrients Deep water / Winter Shallow water / Summer

  22. PAR = photosynthetically active radiation (visible light wavelengths)

  23. Light attenuates exponentially with depth Iz Z0 Z Beer-Lambert Law Iz = irradiance at depth z Units of [Watts m-2] or [mol photons m-2 s-1] k = attenuation coefficient

  24. Average Primary Production saturates at high PAR (photosynthetically active radiation) Inside Fe patch Outside Fe patch Hiscock et al. 2008

  25. Adaptation to different light levels 1 0 Irradiance Photo-inhibition at high light levels Ryther 1956

  26. Diatoms most adapted to low-light conditions Light Intensity / Irradiance Low High Narrow Broad Light Spectrum Low High Temperature High Low Nutrients Deep water / Winter Shallow water / Summer

  27. Attenuation varies with wavelength. More wavelengths are available near the surface. Plankton from stratified, low-nutrient regions thrive by using accessory pigments to harvest more light. violet red

  28. Different color pigments absorb different wavelengths of light Pigments (colored molecules) Phytoplankton with different pigments Chlorophyll*

  29. Phytoplankton with multiple pigments capture more wavelengths • All phytoplankton have chlorophyll • Coccolithophores and diatoms have carotenoids • Cyanobacteria have phycoerythrin, phycocyanin

  30. Coccolithophores and Cyanobacteria most adapted to broad spectrum of light found in shallower mixed layer Light Intensity / Irradiance Low High Narrow Broad Light Spectrum Low High Temperature High Low Nutrients Deep water / Winter Shallow water / Summer

  31. Growth-temperature curves vary among species but share upper limit Upper limit (Eppley 1972) Growth rate Temperature oC

  32. Diatoms grow fastest at low temperatures Diatoms Flagellates Divisions per day Temperature oC

  33. Diatoms most adapted to colder temperatures Light Intensity / Irradiance Low High Narrow Broad Light Spectrum Low High Temperature High Low Nutrients Deep water / Winter Shallow water / Summer

  34. Keep in mind the physics & chemistry of the mixed layer Wind Light & Heat Nutrients

  35. Draw the mixed layer here

  36. Compensation & Critical Depth Photosynthesis Respiration Depth Depth + biomass - biomass (Requires light) (Independent of light)

  37. Compensation Depth R P P>R Biomass increases P = R Compensation depth P<R Biomass decreases Depth

  38. Critical Depth R P Gross Primary Production (GPP) Sum of Respiration (R) Depth GPP=R Net Primary Production (NPP) = 0 Critical depth 0

  39. If critical depth > mixed layer depth, GPP>R, NPP >0 R P Gross Primary Production (GPP) Sum of Respiration (R) Depth Bottom of mixed layer Critical depth

  40. If critical depth < mixed layer depth, GPP<R, NPP<0 R P Gross Primary Production (GPP) Sum of Respiration (R) Depth Critical depth Bottom of mixed layer

  41. Critical depth concept is critical! Respiration Photosynthesis • Understand why R is a straight line • Understand why P is an exponential curve • Know the difference between: critical depth and compensation depth Depth

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