C-MORE Schofield Lecture 3
Transcript of C-MORE Schofield Lecture 3
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C-MORE 2012: Measuring phytoplankton productivity &biomass
Oscar Schofield
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Photosynthesis = PAR * * f
aph =
a(l )*Eo(l )dl400nm
700nm
Eo(l)d
l400nm
700nm
Spectrally averaged absorption
Energy that is into the cellVaries with cell pigmentation,
light history, and size
~ 1%
)()()(
dd
d EKdz
dE
0.00 0.20 0.40 0.60 0.80 1.00
Irradiance
0.00
20.00
40.00
60.00
80.00
100.00
Dep
th
(m
)
Scalar visible irradiance
Energy into the oceanVaries with depth according to the IOPsIOPs with radiative transfer eqns describe the AOPS
Efficiency of converting energy intoEnd product (electrons, oxygen, carVaries with end product and physiolo
Quantum efficiency of ..
High
Low
Absorption
Fluorescenceor chargeseparation
oxygen
carbonfixation
growth
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Enough energy make something new(rearrange a molecule)
Enough energy to excite(vibrate a molecule) Enough energy move electrons
Phytoplankton growth and nutrient assimilation is tied to ambient light levels.
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Every day, the ocean changes colour or rather, it passes though a varietyof hues between the morning, noon
and night of a single day. The subtleshapes of clouds, the glittering light
of the sun, and the shifts in
atmospheric pressure tint the seawith deep tones, cheerful tomes,
plaintive tones that would cause anypainter to pause in wonder.
from The Samurai by Shusaku Endo(1980)
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Eyeball Optics
The Secchi Disk:
First systematic usage reported in 1866, but
observed and remarked upon much earlier.
Early experiments carried out by Commander
Cialdi, head of the Papal Navy, and Professor
Secchi onboard the SS LImmacolata
Concezione (Cialdi, 1866).
Used operationally for establishing aids to
navigation over shallow water.Thanks to Marlon Lewis
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Eyeballs Watch Harmful Algal Blooms
HABs
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The underwater light field is not a collimated beam.
So we define another term(s), the diffuse attenuationcoefficient(s), K, to describe the penetration of light in
the sea. It is closely related to absorption.
~ 1%
Optical Properties of the Sea
)()()(
dd
d EKdz
dE
0.00 0.20 0.40 0.60 0.80 1.00
Irradiance
0.00
20.00
40.00
60.00
80.00
100.00
Dep
th(m
)
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From John T. O. Kirks billabongs
Measuring the light into the system
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Reflectance() = G* bb()/{bb() +a()}
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primary productivity
or export productivity
(Behrenfeld and Falkowski, 1997)
(Muller-Karger et al., 2005)
Wh t f th l i l DIMS?
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What are some of the classical DIMS?
laustre et al.
Diatoms Y 0.114 + 0.051Cryptophytes Y 0.053 + 0.011
Y* = P/(Qpar(0+))
Localweather
seasonal
Morel and Platt show Y* variabilityOf 50% around a value of at specific
chl values
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Penetration of light is determined by the material in the waterwhich is determined by the overall inherent optical properties (IOPs)
Absorption (a) color
Photos by S. Etheridge
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Scattering (b) clarity
a + b = c
c = attenuation
From Collin Roesler
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detector detector
Absorption (a)Attenuation (b)
WetLabs
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Scattering Case I waterscp(660) bp(660)
Loisel and Morel 1998Bp ChlAc )660(
Positively correlated Non-linear, B 0.7 High unexplainedvariance
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Particle backscattering
Cannizzaro et al. 2002
West Florida Shelf
Karenia brevisbloom
POC S i (C I )
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POC Scattering (Case I waters)
Loisel and Morel 1998
Bp POCAc )660(
B 1
Subtropical Pacific, North Atlantic
Contrast with non-linear
dependence on Chl
POC-Chl variationsare important
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E.m. radiation propagating as plane waves;g
geometric cross
section (its shadow )
EFFICIENCY FACTORS
Energy absorbed withinEnergy scattered out by..
Divided by
Energy impinging on g
Qa and Qb, respectively
From beautiful work of Morel, Bricaud, and Kirk
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(Finkel 2001)
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Durand et al. 2002
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Positivelycorrelated
Chl: 0.02 25mg m-3
(eutrophic,mesotrophic, and
oligotrophic
waters) Bricaud et al. 1995 Non-linear dependence
Thanks to Heidi Sosik
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Chl-specific phytoplankton
absorption Second-ordervariability in aph()
)(* )()( Bph ChlAa
Chl
aa
ph
ph
)()(*
A() and B()
statistically determined
This reflects effects of changing growth conditions andcommunity structure with trophic status
Note: unexplained variability
Negatively correlated
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Low light
High light
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Low light
High light
Photosyntheticpigments
Photo-protectivepigments
chlorophyte alga Haematococcus pluvialis
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0
5
10
15
20
400 450 500 550 600 650 700
Wavelength (nm)
SpectralIrr
adiance(
mW
cm-2nm-1)
chl a chl achl b
chl c
chl bcarotenoids
phycobilins
0
0.25
0.50
0.75
1.0
1.25
RelativeAbsorption
chl a-chl c-carotenoidschl a-chl b-carotenoids
chl a-phycobilins
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2 0 22 0 42 0 62 0 82 1 02 1 22 1 4
0
2
4
6
8
0
2
e
p
t
h
(
m
2 0 22 0 42 0 62 0 82 1 02 1 22 1 4
0
2
4
6
8
0
2
e
p
t
h
(
m
mo
lpho
tons
(m-2
s-1)
Dep
th(m)
Calendar DayB
mol photons m-2 s-1
C
Calendar Day
D
(m-1)pha
Dep
th(m)
0 22 0 42 0 62 0 82 1 02 1 22 1 4
500
1000
1500
2000
0400 450 500 550 600 650 700
0
0.3
0.6
0.9
1.2
surface
1m
2m
5m13m
Wavelength (nm)Calendar Day
A
. . . .
Oliver et al. 2004
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0.0
0.02
0.04
0.06
0.08
400 450 500 550 600 650 700
chl achl b
chl c
PSC
PPC
wavelength (nm)
absorptioncoefficient(m2m
g-1)
From Bidigare
Individual pigments can be measured on discrete samples biochemically
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0
20
40
60
80
1000 1 2 3
D
epth(m)
Relative pigment-specific
spectrally weighted absorption
B)
Decreasing efficiency Increasing efficiency
Chl a
Chl bPSCChl c
Wavelength (nm)
0.00001
0.0001
0.001
0.01
0.1
1
10
400 500 600 700Spectralirradiance(mWcm-2s-1)
1
25
90
Sun stimulated
fluorescence
A)
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Absorbed photon Charge stabilization &
photosynthesis
Heat
Fluorescence
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Chlorophyll a -Fate of photonsabsorbed by an isolated molecule
Diagram of energy states in chlorophyll and possible
transitions
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Alexander Graham Belldeveloped spectrophone,
essentially an ordinaryspectroscope equipped with
a hearing tube instead of aneyepiece listening to lightinduced changes in the
thermal sound.
Light Absorption
Heating
Thermal Expansion
PressureWave
Photoacousticsignal
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Weak light flash
Strong light flash
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Absorbed photon Charge stabilization &
photosynthesis
Heat
Fluorescence
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Fluorescence
Use of sun-induced chlorophyll
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Use of sun induced chlorophyllfluorescence to estimate the rate of
carbon fixation -Example
Stegmann et al. (1992)
JGR
Pacific
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Chloroph
yll
fluorescence
Chlorophyll concentration
Stress(light, nutrients)
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8:00 12:00 18:00 22:00
5
10
15
20
Local DaylightTime
0
Depth(m)
CDOM
8:00 12:00 18:00 22:00
5
10
15
20
0
D
epth(m)
Chl a
mixed
chromophyte
community
m
onospecific
G.breve
c
ommunity
Local DaylightTime
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0.00
0.25
0.50
0.75
5:00 9:00 13:00 17:00 21:00
0
400
800
1200
1600
PAR
molm-2
s-1)
Fv/Fm
EPS
Local Daylight Time
0
0.2
0.4
0.6
6:00 10:00 18:0014:00
Local Daylight Time
Fv/F
m
0
200
400
600
800Visible light downregulation
UVB
damage
PAR(
molm-2
s-1)
UVB + UVA + PAR
UVA + PAR
PAR
Ik>PARIk>PAR
Physiological response Environmental Stress
Falkowski et al. (1991) Nature
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Falkowski et al. (1991) Nature
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Fluorescence: The Basics
F0 = aph PARkf
kp +kf+kd
Fm = aph PARkf
kf+kd
Fv = aph PARkf
kp(Q)+kf+kd
Fm - F0
Fm=
kp
kp +kf+kd= f IIeo
time
Fluorescence
intens
ity
F0
Fm
Ft
Saturating flash
Fm
Other useful indices
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Time
Fluorescencerise
Integrated area isreflection of the absorption
cross-section
Flash is on RC2
Highlightcells
Lowlightcells
Photo-acclimation
Photons
Ot e use u d cesFLUORESCENCE INDUCTION
O
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0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800
Fluorescence
decaycons
tan
ts
Local time of day
Time
Other useful indicesFLOURESCENCE DECAY CONSTANTS
LightFlash
TurnedOff
Fluorescenc
e
RC
Pheo
Qa
Qb
PQ
D1
D2
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Absorbed photon Charge stabilization &
photosynthesis
Heat
Fluorescence
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Light Reactions produce ATP, NADPH2
Light
Transmission& light absorption
Light Reactions Dark Reactions
ATP& NADPH
CO2 sugars& carbos
Cellular Growth
Nitrogen,
Phosphorus,Metals
BiomassIncrease
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0
2
4
6
8
10
0.1 1 10 100 1000
0.4
0.5
0.6
0.7
0.8
Irradiance (mmol photons m-2 s-1)Prod
uctivity(mg
CmgChla-2h
-1)
0
0.02
0.04
0.06
0.08
0.1
CarbonQ
uantumYield
(molCmolphotonsabsorbed-1)
Fv/Fm
a
Pmax
Ik
fmax
Environmentalstress
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Production = Pmax. tanh(PAR/Ik)
Pmax
a
Ik = Pmax/a
PAR (mmol photons m-2 s-1)
oxygen
evo
lution
0
1
2
3
4
0 50 100 150 200 250 300
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fluorescence-based predictions of oxygen evolution
measuredoxyge
nevolution
0
1
2
3
4
5
6
0 1 2 3 4 5 6
R2=0.92, P
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From Jassby and Platt 1976
Is a cell a puddle or lake?
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Chl-specific alpha
0
20
40
60
80
100
0.02 0.03 0.04 0.05 0.06 0.07 0.08
aw a
light-limited
(mg C mg chl a-1 h-1[ mol photons m-2 s-1]-1)
depth(m
)
light-saturated
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Photosynthesis a chain of cascading reactions:
Each step sets the upper limit efficiency for each following step down the line
Fmpsii (0.65) > fm02 (on the order 0.125)>fmco2 (on the order 0.07)
For each use of energy go to one process, it is the expense of
another reaction, this impacts the overall efficiency
Nutrient source fmco2Ammonium 0.09Nitrate 0.07
Simplest expression for photosynthesis is
P = f * aph * PAR
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From Behrenfeld et al.
The conversion efficiency can varies between end products
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0
2
4
6
8
10
12
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Absorbed Quanta by phytoplankton
Light-saturated photosynthesis
Light-limitedphotosynthesis
Ra
tioo
fOxygen
toCar
bon
Quan
tum
Y
ields
The conversion efficiency can varies between end products
While chlorophyll specific absorption varies 3-4 foldt i ld b d f it d
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From Babin et al.
quantum yields vary by an order of magnitude
Even in 1980s was treated as a constant
NUTRIENT LIMITATIONS
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U O S
Iron-Ex
)Roug
h seas
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50 100 150 200 250 300 3500.005
0.025
0.045
0.065
0.085
0.105
0.125
1
2
3
45
6
7
8 9
10
11
12
13
14
1516
171819
20
21
22
23
New Jersey Coastal Region22 Southern California Bight21
NW Atlantic Continental Shelf (Spring)
20 Gulf Stream (Spring)19 NW Atlantic Subtropical Gyre (Spring)18 NE Atlantic Subtropical Gyre (Spring)17 Canary Islands (Spring)16 NW Atlantic Continental Shelf (Fall)15 Gulf Stream (Fall)14 NW Atlantic Subtropical Gyre (Fall)13 NE Atlantic Subtropical Gyre (Fall)12 Canary Islands (Fall)11 Antarctic (Palmer Station)10 Antarctic (Transitional Weddell Water)9 Antarctic (Bellingshausen Warm water)
8 Antarctic (Bellingshausen Cold water)7
Arabian Sea (NE Monsoon)
6
Arabian Sea (Inter Monsoon)
5
Arabian Sea (SW Monsoon)
4321
Antarctic (Bransfield-Bellingshausen water)Antarctic (Bransfield-Weddell water)Antarctic (Ice-Edge water)Antarctic (Weddell-Scotia Confluence waters)
23
Ek(PAR) (mol photons m-2 s-1)
max
(molCm
olphotonsabsorbed-1)
Oligotrohicseas
Types of satellite models
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Empirical: Purely a statistical fit. Earliest ones were simple regressionmodels of measured primary production against satellite derivedchlorophyll concentration. These models can explain a lot of the observed
variance; however assume that the fraction of productivity perphytoplankton cell is essentially fixed.
Early models were derived by Smith et al. (1982) and Eppley (1985) atScripps Visibility Labs and Food Chain Working Group
Types of satellite models
Ck = surface chlorophyll concentration, II or Pt = depth-integrated production
Smith & Baker 1978
Eppley et al. 1978
Types of satellite models
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Empirical: It works because, the amount of chlorophyll in a volume ofwater is proportional to the number of phytoplankton cells and the numberof photosynthetic reaction centers. In many ways it provides a goodOckams razor for the sophisticated productivity models.
Problems:
l These relationships assume that the conversion of light energy is constant (nottrue), that the light harvested for within and between phytoplankton is constant (nottrue).
l Chlorophyll is a concentration, productivity is a rate which has a time dependentvariable.
l Scales in which to apply the model?
Applying the razor: Back in early 1990s, many sophisticated bio-opticalproductivity were being developed. A global comparison of the models at thetime indicated that simple correlation models did as well or even sometimesbetter than more sophisticated and biologically realistic models. This did notsit well with some in the community.
Complexity can add uncertainty
The overcome the errors associated with the depth-dependent variabilityY t li t l i d id li d fil
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Platt and Sathyendranath, Science
You generate climatalogies and idealized profiles.
Ignoring the vertical behaviorcan lead to a 30% error
Remember the majority of
phytoplankton biomass is likelylight limited, so the importance
of the upper water column wherelight levels are high dominate
the integrated productivityestimates.
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Relative cloud cover Biogeographic provinces
Monthly weighted chl productivity