1. Prof. Heidi Fuchs

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. 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?
Illustrate principals and processes
Teach you how to read (and draw) different kinds of graphs
When in doubt, think about what’s happening with the physics.

4. 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?
Illustrate principals and processes
Teach you how to read (and draw) different kinds of graphs
When in doubt, think about what’s happening with the physics. Ask questions!

5. An informal survey…

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

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

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

9. 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 - ΣR
Need GPP>ΣR for net growth!

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

11. “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.

12. Four major players Cyanobacteria Diatoms Coccolithophores
Dinoflagellates
Small (<1 μm) or
Large (0.5-4 mm)
Nitrogen fixers
Large (2-200 μm)
Have silica frustules
Small (2-25 μm)
Have CaCO3 tests
Large ( μm)
Have unique life
cycle & blooms

13. What limits production?
Nutrients
Light
Intensity
Spectrum
Temperature
Grazing by zooplankton
Write the general equation on the board here

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

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

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

17. Growth rate varies with [nutrient]
μ = Specific growth rate (d-1)
Curve “saturates”
Specific growth rate is defined as the increase in cell mass per unit cell mass per unit time
N = [Nutrient]

18. Growth rate varies with [nutrient]
μ = Specific growth rate (d-1) Ks
μmax/2
μmax
Michaelis-Menten Kinetics
Specific growth rate is defined as the increase in cell mass per unit cell mass per unit time
“half-saturation
constant”
N = [Nutrient]

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

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

21. PAR = photosynthetically active radiation (visible light wavelengths)
Irradiance = power of electromagnetic radiation per unit area of ocean’s surface (e.g. W m-2) - or -
energy per area per time (e.g. mol photons m-2 s-2).

22. Light (PAR) attenuates with depthIz Z0
Iz = irradiance at depth z
Units of [Watts m-2] or
[mol photons m-2 s-1]
Light attenuates as it is absorbed and scattered by particles in the water. Z

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

24. Species adapt to different light levels
Irradiance 1
Photo-inhibition
at high light levels
Ryther 1956
Too much light damages cells and reduces photosynthesis (photo-inhibition)

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

26. Attenuation varies with wavelength.
More wavelengths are available near the surface.
Plankton use colored pigments to harvest light at different wavelengths.
violet red

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

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

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

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

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

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

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

34. Primary production varies with depth
Photosynthesis
Respiration
Depth
Depth +
biomass -
biomass
(Requires
light)
(Independent of
light)

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

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

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

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

39. 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