Today:

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Today -Review light (Quick) -Productivity -Nut
rient limitation -Trophic levels -Ocean
Ecosystem Productivity
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0
B)
Chl a
Chl b
20
PSC
Chl c
40
Depth (m)
60
80
Decreasing efficiency
Increasing efficiency
100
0
1
2
3
Relative pigment-specific spectrally weighted
absorption
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surface
µmol photons (m-2 s-1)
E (?) normalized to 570 nm
1m
2m
5m
13m
A
C
Wavelength (nm)
Calendar Day
Depth (m)
Depth (m)
B
D
Calendar Day
Calendar Day
µmol photons m-2 s-1
(m-1)
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0.08
chl a
chl b
0.06
chl c
PSC
PPC
0.04
absorption coefficient (m2 mg-1)
0.02
0.0
400
450
500
550
600
650
700
wavelength (nm)
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Phytoplankton absorption

• Positively correlated
• Chl 0.02 25 mg m-3
• (eutrophic, mesotrophic, and oligotrophic waters)

Bricaud et al. 1995
? Non-linear dependence
Thanks to Heidi Sosik
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Chlorophyll a - Fate of photons absorbed by an
isolated molecule
Diagram of energy states in chlorophyll and
possible transitions
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CO2
QA
Fd
CH2O
Fluorescence
QB
2H
e -
PQH2
RC II
RC I
P680
2H
z
Light harvesting Pigments
O2 4H
2H2O
Light
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NUCLEUS
LHC gene
Repressor proteins
CYTOSOL
CHLOROPLAST
1/2CH2O 3/2ADP 3/2Pi
H 1/2CO2
Days to Weeks
6H
NADPH
H NADP
3/2ATP 3/2Pi
3/2ADP 3/2Pi
Fd
2H
2H
STROMA
Qb
Fa/ Fb
CF1
PQ
2 x e-
PQ
Qb
PQ
Qb
Fx
PQ
PQ
D1
e-
THYLAKOID MEMBRANE
D2
ATP synthase complex
A0
Cytochrome b6-f-Fenn
Pheo
Photosystem II
Photosystem I
e-
CF0
P700
P680
PC/ cyt c6
PH
E
E
Minutes to Hours
e-
4Mn
Yz
fluorescence
2H
2H
1/2 O2 2H
H2O
THYLAKOID LUMEN
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Light Reactions produce ATP, NADPH2
Transmission light absorption
ATP NADPH
Light
Light Reactions
Dark Reactions
Nitrogen, Phosphorus, Metals
CO2
sugars carbos
Biomass Increase
Cellular Growth
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NUTRIENTS!!!!
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Chlorophyll a emits red light when excited with
blue or red light !
Thanks to Marcel Babin
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Why Chlorophyll Fluorescence?
1) Fundamental property to all photosynthetic
organisms 2) Simple to measure (especially
compared to other traditional photosynthetic
measurements, 14C-uptake or O2 evolution) 3)
Represents a technology which can be converted
for remote sensing and/or field instruments
(submersible units, moorings, LIDAR) 4)
Can assess many important biological
properties -photosynthetic state of plants
(light-limited?) -photoadaptive state (acclimated
to environment?) -community composition -assess
environmental stress on a plant bright light
stress, temperature stress, pollution effects,
ultraviolet radiation
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Production Pmax . tanh(PAR/Ik)
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Pmax
3
a
oxygen evolution
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Ik Pmax/a
1
0
0
50
100
150
200
250
300
PAR (mmol photons m-2 s-1)
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  Phytoplankton organic matter is made up of a
large number of organic compounds (e.g. proteins,
lipids, carbohydrates), but on average it has
atomic ratios of C to N to P of 106 to 16 to
1.   Thus, the process of photosynthesis can be
represented as
hv 106CO2 122H2O
16HNO3 H3PO4
(CH2O)106(NH3)16H3PO4 138O2   This reaction
illustrates the need for the nutrients nitrate
and phosphate. It also shows that for every 106
CO2 molecules taken up, approximately 138 O2
molecules are liberated.  
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Surface distribution of chlorophyll a using
SeaWiFS data sets Note physical forcing effects
Coastal, Equator, North Atlantic
SeaWiFS Team/GSFC/NASA
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Nutrient Limitation
Many elements are necessary for life, but only
those in short supply are limiting to
photosynthesis. Oceanographers consider nitrate,
phosphate, silica, iron and several other trace
metals to be the most biolimiting elements.
Silicon is important for the growth of diatoms.
Iron is required for photosynthetic electron
transport and the synthesis of chlorophyll.   Nutr
ient profiles generally increase with depth.
Concentrations may be below detection in surface
waters, especially in the open ocean.  
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Light Reactions produce ATP, NADPH2
Transmission light absorption
ATP NADPH
Light
Dark Reactions
Light Reactions
Nitrogen, Phosphorus, Metals
CO2
sugars carbos
Biomass Increase
Cellular Growth
FOOD WEB
Regenerated Production
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Gephyrocapsa oceanica
Pyramimonas parkeae
Dunaliella tertiolecta
Thoracosphaera heimii
Diatom sp.
Ditylum brightwellii
Ceratium sp.
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VVmaxS/(KsS)
Austin Powers Fat Bastard System
Miss Manner System
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Different Strategies of Nutrient Utilization

• Coccolithophores
• Low Vm
• Low Ks

• Diatoms
• High Vm
• High Ks

High or fluctuating nutrients High mixing,
upwelling Low average irradiance, light
fluctuations High turbulence
Chronically oligotrophic Stratified
conditions High average irradiance Low turbulence
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Thanks to Elena Litchman
Nutrient Uptake Varies with Phytoplankton Species
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Nutrient sources to surface waters are rivers
and land runoff upwelling atmosphere   The most
productive regions of the oceans are the coastal
regions because this is where upwelling is
strongest and where river and land runoff meet
the sea. Here nutrients result in high
productivity rates, which in turn result large
fisheries.  
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New Jersey Coastal Upwelling
Barnegat
Cape May
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So Plants Need Light and Nutrients

• Light Limitation in the Oceans

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net photosynthesis
net primary production
phytoplankton respiration
community respiration
Z (meters)
euphotic zone
Critical depth NPP Rc Note these are
integrated over the water column.