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

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

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

Quantum Yield Absorption vs. Quantum Yield….

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

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

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

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)

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)

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)

Coastal Water

Red algae and Cyanobacteria Chlorophyll Chlorophyll Phycobilins

Red algae: Complementary chromatic adaptation (?) Phycobilins

Zones according to LIGHT: Euphotic Disphotic Aphotic Fig 2.5

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 +

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

C:N = 6.6

What determines nutrient uptake into plants?

How do we know if a nutrient is limiting?

Seawater Nitrogen* 0.05-1.0 mM (NO3-, NH4+) Phosphorous* 0.005-0.1 mM (PO42-) Silica (Si) 0.5-5 mM Iron (Fe) ?

Is it ethical? Is it leagal?

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

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.

Temperature Usually 4oC at depths “Thermocline”

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

measured in permill (o/oo, g/l), Usually ~ 35-40 o/oo (=3.5 - 4%) Salinity measured in permill (o/oo, g/l), Usually ~ 35-40 o/oo (=3.5 - 4%) o/oo (or units) Open ocean 32 - 38 Shallow coastal 27 - 30 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

Salinity: Eurohaline / Stenohaline species 6 38 40 Salinity: Eurohaline / Stenohaline species

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

Salinity can be toxic! Seawater ~0.5 M NaCl Salts mM NaCl 500 MgSO4 30 Open ocean 32 - 38 Shallow coastal 27 - 30 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

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

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

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

350 ppm CO2 = 15 μM 10 μM CO2 CO2 + H2O > H2CO3 > HCO3- + H+ > CO32- + H+ pH 8.2: 10 μM 2000 μM 300 μM Inorganic Carbon (Ci) ~2.1 mM HCO3-