1. Marine Botany
Lesson 4 (continued from last week): The physical and chemical environment relevant to marine plant growth in the oceans…

2. Abiotic = Physical / Chemical Conditions affecting Plant Growth
Light – Irradiance
Nutrients
Temperature
Salinity (ions, including CO2 >>> HCO3-) pH

3. Measuring Light (Ft. Candles) (Energy)
Photon Flux (mol photons m-2 s-1); [mol photons = Einstein (E)]
Sunny day: ~ 2000 mmol photons m-2 s-1

4. Quantum Yield
Absorption vs. Quantum Yield….

5. Blue-photon excitation level
Chlorophyll
Heat
Photosynthesis
Fluorescence Ph
Blue-photon excitation level
Red-photon excitation
level
Ground state
red
orange
yellow
green
blue
Electron energy level

6. Measuring Light (Ft. Candles) (Energy)
Quantum E = h*c / λ
Because the quantum yield for photosynthesis is equal for all wavelengths of PAR, we measure light as PHOTON FLUX
(Ft. Candles)
(Energy)
Photon Flux (mol photons m-2 s-1); [mol photons = Einstein (E)]
Sunny day: ~ 2000 mmol photons m-2 s-1

7. As light hits water surface: Reflectance Attenuation: Absorption
Irradiance
Depth
linear scale
log scale
As light hits water surface:
Reflectance
Attenuation: Absorption
Scatter
Absorption of low energy
PAR (high wavelengths),
Scatter of short wavelengths
PAR (low wavelent
Exponential attenuation!!!
Attenuation

8. Light:
Light is Reflected by the water surface, and Attenuated by the water column
Reflection: 5-70% depending on Solar Angle and Roughness
Attenuation: by Absorption and Scatter
Absorption: Exponential, Selective [(Low-energy photons (red) are absorbed more than high-energy photons (blue)]
Scatter: Short wavelengths (blue) are scattered more than long wavelengths (red)

9. Reflection: 5-70% depending on Solar Angle and Roughness
Clear Oceanic Water
Light:
Light is Reflected by the water surface, and Attenuated by the water column
Reflection: 5-70% depending on Solar Angle and Roughness
Attenuation: by Absorption and Scatter
Absorption: Exponential, Selective (Red is absorbed more than Blue)
Scatter: Short wavelengths (blue) are more scattered than Long wavelengths (red)

11. Light:
Light is Reflected by the water surface, and Attenuated by the water column
Reflection: 5-70% depending on Solar Angle and Roughness
Attenuation: by Absorption and Scatter
Absorption: Exponential, Selective (Red is absorbed more than Blue)
Scatter: Short wavelengths (blue) are more scattered than Long wavelengths (red)

13. Coastal Water

15. Red algae and Cyanobacteria
Chlorophyll
Chlorophyll
Phycobilins

16. Red algae: Complementary chromatic adaptation (?)
Phycobilins

17. Zones according to LIGHT: Euphotic Disphotic Aphotic
Fig 2.5

18. 1Compensation Irradiance (Ic) ~ 1% of full surface light/
2Compensation Depth = depth where 1% of surface light remains
– depends on water clarity!
Euphotic Zone
~1% 2 1
Photosynthesis and
- Productivity +

19. Abiotic, Physical / Chemical Conditions
Light – Irradiance
Nutrients
Temperature
Salinity pH

20. C:N = 6.6

22. What determines nutrient uptake into plants?

23. How do we know if a nutrient is limiting?

24. Seawater Nitrogen* 0.05-1.0 mM (NO3-, NH4+) Phosphorous* 0.005-0.1 mM
(PO42-)
Silica (Si) mM
Iron (Fe) ?

26. Is it ethical? Is it leagal?

27. Abiotic, Physical / Chemical Conditions
Light – Irradiance
Nutrients
Temperature
Salinity pH

28. Eurobiotic / Stenobiotic Eurothermic / Stenothermic
Controls rates of reactions
Controls solubility of gasses
Determines density
Temperature
“Isotherms”
Fluctuations: <1o daily, 0-5o yearly in arctics / tropics, more in temp/subtr.

29. Temperature
Usually 4oC at depths
“Thermocline”

30. Abiotic, Physical / Chemical Conditions
Light – Irradiance
Nutrients
Temperature
Salinity pH

31. measured in permill (o/oo, g/l), Usually ~ 35-40 o/oo (=3.5 - 4%)
Salinity
measured in permill (o/oo, g/l), Usually ~ o/oo (= %)
o/oo (or units)
Open ocean
Shallow coastal
Estuary 0 – 30 brackish
Semi-enclosed sea < 25 brackish
Hypersaline sea > 40
Seawater ~0.5 M NaCl
Salts mM
NaCl 500
MgSO4 30
CaCl2 10
KCl 10
HCO3- ~2 mM

32. Salinity: Eurohaline / Stenohaline species6 38 40
Salinity: Eurohaline / Stenohaline species

33. Usually 4oC at depths Temperature
“Halocline” = salinity boundary, can be saline on bottom water (usually) or top water (Med)
“Thermocline”

34. Salinity can be toxic! Seawater ~0.5 M NaCl Salts mM NaCl 500 MgSO4 30
Open ocean
Shallow coastal
Estuary 0 – 30 brackish
Semi-enclosed sea < 25 brackish
Hypersaline sea > 40
Seawater ~0.5 M NaCl
Salts mM
NaCl 500
MgSO4 30
CaCl2 10
KCl 10
HCO3- ~2 mM

35. Na Cl K
Internal Concentration of NaCl: ~ 80 mM (vs. 500 mM in seawater

36. Abiotic, Physical / Chemical Conditions
Light – Irradiance
Nutrients
Temperature
Salinity
pH? Carbon!

37. pH ~8.2 pH Seawater ~0.5 M NaCl Salts mM NaCl 500 MgSO4 30 CaCl2 10
KCl 10
HCO3- 2.2
pH ~8.2

38. 350 ppm CO2 = 15 μM
10 μM CO2
CO2 + H2O > H2CO3 > HCO3- + H+ > CO32- + H+
pH 8.2: 10 μM μM μM
Inorganic Carbon (Ci) ~2.1 mM HCO3-