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• Phytoplankton bloom– there is no officially recognized threshold level– range from 10,000s – 1,000,000s of cells per ml
Primary Production: Definitions and P vs. I
OutlineReview LightBeer’s LawPigments
PhotoadaptationPhotosynthesis
Primary ProductivityP vs. I Curves
More Aquatic Habitats (Vertical)
Continental Shelf
Continental S
lope
Abyss … Trench
1% Light Depth
Neritic OceanicCoastal
Euphotic zone
Permanent Thermocline
Bathypelagic
mesopelagic
EPIpelagic25m
100m
1000m
200m
Abyssopelagic
Not shown:
Seasonal Thermocline (varies, 10 – 400 m, depending on season and location)
What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light
Absorbed PAR
What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light
Absorbed PAR
• Scattered back out into the atmosphere
Can be detected by sensors in air or orbit
What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light
Absorbed PAR
• Scattered back out into the atmosphere
Can be detected by sensors in air or orbit
• Absorbed by waterHeats it up
What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light
Absorbed PAR
• Scattered back out into the atmosphere
Can be detected by sensors in air or orbit
• Absorbed by waterHeats it up
• Absorbed by plant pigmentsPhotosynthesis
What happens to absorbed light?Photosynthetically active radiation (PAR) 400 – 700 nm or visible light
Absorbed PAR
• Scattered back out into the atmosphere Can be detected by sensors in air or orbit
• Absorbed by waterHeats it up
• Absorbed by plant pigmentsPhotosynthesis
• Absorbed by dissolved materialsPhotochemistry
• Attenuation = a decrease in the energy of light due to absorption and scattering in the water column
• Attenuation coefficient (K) = describes the exponential decay of light with depth within the water column
Irradiance in the OceanIrradiance in the Ocean
Iz = irradiance at depth z
I0 = irradiance at surface
k = attenuation coefficient (m-1) (k also called absorption or extinction coefficient)
Iz = I0 e-kz
Beers LawI
z
Phytoplankton Pigments
• Pigments
Organic compounds (or organometals) that absorb light.
• Pigment – protein (complexes)
Include chromophores (pigment molecules) bound covalently to protein structures.
Roles of Pigments
• Absorb light energy for photosynthesis(Light Harvesting)
• Intercept or dissipate harmful light energy(Photoprotection)
• Convert light energy into chemical energy(Photochemistry)
Pigment analysisPigment analysisFluorometer
Shine blue light Fluoresces red
Chromatography
HPLC machine
Classes of Pigments in Marine Plants • Chlorophylls - Porphoryn rings, magnesium in
center (light harvesting and photochemistry)– Chl a– Chl b – Chl c
Classes of Pigments in Marine Plants • Chlorophylls - Porphoryn rings, magnesium in center
(light harvesting and photochemistry)– Chl a– Chl b – Chl c
• Carotenoids – carotenes simple chains of carbon and hydrogen (photoprotection)– Xanthophylls 400-500 nm gives brown color to marine plants– Beta-carotene does not feed energy in but absorbs light for
plants (sunscreen) protects phototrap from receiving too many electrons
– Fucoxanthin 510-525 nm give diatoms brown, olive-green color
Classes of Pigments in Marine Plants • Chlorophylls - Porphoryn rings, magnesium in center (light harvesting and
photochemistry)– Chl a– Chl b – Chl c
• Carotenoids – carotenes simple chains of carbon and hydrogen (photoprotection)– Xanthophylls 400-500 nm gives brown color to marine plants– Beta-carotene does not feed energy in but absorbs light for plants
(sunscreen) protects phototrap from receiving too many electrons– Fucoxanthin 510-525 nm give diatoms brown, olive-green color
• Biliproteins water soluble accessory pigments (reds, blues, purples) (photosynthetic light harvesting only)– Phycoerythrin 500-570 nm, Phycocyanin 550-650 nm
(red orange)
Absorption of light by Phytoplankton Absorption of light by Phytoplankton PigmentsPigments
400
500
600
700
Visible(PAR)
Photoadaptation
• phytoplankton manufacture more chlorophyll – Increase umbrella to catch more of the sun's rays
• phytoplankton manufacture accessory pigments– expand the color range over which light can be
captured
• phytoplankton manufacture a set of pigments called protective pigments (carotenoids)– prevent intense sunlight from damaging the
photosynthetic apparatus, wide absorption bands that capture light energy and turn it into heat = photoinhibition
Antenna
• Complicated array of accessory pigments
(carotenes, xanthophylls, phycobilins)
Why do we care about pigments?
Some planktonic algae have large amounts of accessory pigments as well as Chl. What would the benefit be to that cost?
Biogeochemical Perspective on Biological Oceanography
• Rate Processes: Chemical transformations in the environment
Primary productivity (Photosynthesis and Respiration)
Remineralization
• Concept: Control of rate processes
• Concept: Limitation of rate processes
Primary Production (PP)
• The amount of autotrophic biomass produced per unit area (or vol) per unit time.
PP P – R
PP rate is independent of biomass eaten by grazers, lost to sinking, etc.
range from 1-5 g C/ m-2/ year-1 (central gyres)
to 200-400 g C/ m-2/ year-1 (upwelling areas)
Photosynthesis
• Photosynthesis
6CO2 + 6H2 O → C6H12O6 + 6 O2
LIGHT & pigmentsLIGHT & pigments
• Respiration
6CO2 + 6H2 O ← C6H12O6 + 6 O2
Photosynthesis• Photosynthesis
6CO2 + 6H2 O → C6H12O6 + 6 O2
• Respiration
6CO2 + 6H2 O ← C6H12O6 + 6 O2
• Expressed as the RATE per VOLUME of the BIOMASS produced (mg C m-3 h-1)
the BIOMASS-SPECIFIC rate: (mg C mg Chl a-1 h-1) <- Assimilation Number
Photosynthesis can be expressed as:• Amount of carbon fixed OR • Amount of oxygen released
IMPORTANT NOTE: Photosynthesis is not equal to Primary Production
Example: Organisms also do RESPIRATION (R)
CH2O + O2 → CO2 + H2O + Energy
• Gross Primary Productivity (Pg)
– Total PP
• Net Primary Productivity (Pn)
– Gross PP – plant respiration
• Primary Productivity (PP) rate
• Respiration (R) rate
• Photosynthesis (P) rate
= mass/area or volume/time
mg O2/l/t
Estimating Primary Productivity
In a bottle of known volume, incubate for a whole day.
P and R →
← R
1) Measure the increase in oxygen over a given period of time2) Measure the uptake of labeled carbon (14C) by the phytoplankton.
GROSS Primary Production Rate
NET Primary Production Rate
Pg – R = Pn
PhotosynthesisIs a function of VISIBLE LIGHT
Photosynthetically Available Radiation (PAR)Quantity of light that stimulates photosynthesis
The relationship between Photosynthesis and Irradiance (PAR) is called the P-I CURVE
Photosynthesis – Irradiance Curve
• P is the photosynthesis rate (matter / volume*time)• I is the irradiance, light intensity (cal cm-2 min-1)
1 cal cm-2 min-1 (PAR) =3.15x10-4 μmol m-2 s-1
P
Irradiance (I or E)
Photosynthesis – Irradiance Curve
• Pmax is the maximal rate of photosynthesis• Ik is the irradiance saturation parameter (varies for
different plants)• is the initial slope of the P vs. I curve
P
Irradiance (I or E)
Pmax
Ik
Photosynthesis – Irradiance Curve
• Ib is the irradiance at which photoinhibition occurs
• is the decrease in P with increasing irradiance under photoinhibition.
P
Irradiance (I or E)
Pm
IkIb
Photosynthesis – Irradiance Curve
• Changes in reflect changes in the light harvesting capacity and efficiency of the light reactions of photosynthesis (cellular properties)
• Changes in Pm reflect changes in the enzymatic capacity (e.g. the dark reactions of photosynthesis).
P
Irradiance (I or E)
Pm
IkIb