modeling phytoplankton community structure: pigments and scattering properties stephanie dutkiewicz...
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MODELING PHYTOPLANKTON COMMUNITY STRUCTURE:
PIGMENTS AND SCATTERING PROPERTIES
Stephanie Dutkiewicz1
Anna Hickman2, Oliver Jahn1, Watson Gregg3, Mick Follows1
1. Massachusetts Institute of Technology2. University of Essex
3. NASA Goddard Space Flight Center
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
http://darwinproject.mit.edu
modeling the marine ecosystem
nutrients
light
many (100+)phytoplankton
zooplankton
detritus
some sinks out to depthsDarwin Project Model(Follows et al., Science 2007)
PO4NO3
FeSi
randomly assignedgrowth rates
grazing rates
http://darwinproject.mit.edu
modeling the marine ecosystem
nutrients
light
phytoplankton
zooplankton
detritus
some sinks out to depths
PO4NO3
FeSi grazing rates
randomly assignedgrowth rates
Darwin Project Model(Follows et al., Science 2007)
environment 1
http://darwinproject.mit.edu
modeling the marine ecosystem
Darwin Project Model(Follows et al., Science 2007)
nutrients
light
phytoplankton
zooplankton
detritus
some sinks out to depths
PO4NO3
FeSi
grazing rates
environment 2
randomly assignedgrowth rates
http://darwinproject.mit.edu
log10(biomass)
Initial Biomass of 100 phytoplankton types
http://darwinproject.mit.edu
log10(biomass)
Annual Biomass after 10 years simulation
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
EMERGENT COMMUNITY
By putting in appropriate trait trade-offs, environment selects the appropriatecommunity structure:
- K versus r strategies (Dutkiewicz et al, GBC, 2009)
-nitrogen fixing (Monteiro et al, GBC, 2010,2011)
-nitrate assimilation ability (Bragg et al, PlosOne 2010)
-size/grazing pressure (Ward et al. in prep)
-pigments/absorption (Hickman et al, MEPS, 2010)
Phytoplankton Functional Types
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
EMERGENT COMMUNITY
Phytoplankton Functional Types
By putting in appropriate trait trade-offs, environment selects the appropriatecommunity structure:
- K versus r strategies (Dutkiewicz et al, GBC, 2009)
-nitrogen fixing (Monteiro et al, GBC, 2010,2011)
-nitrate assimilation ability (Bragg et al, PlosOne 2010)
-size/grazing pressure (Ward et al. in prep)
-pigments/absorption (Hickman et al, MEPS, 2010)
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
(Data courtesy: M. Zubkov, J. Heywood)
(Hickman et al, MEPS, 2010)
AMT15
Vertical distribution of phytoplankton types
OBSERVATIONS
ONE DIMENSIONAL MODEL
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
Pigments as trait• Different pigment allow absorption of light at different wavebands
wavelength (nm)
Culture date fromL. Moore, D. Suggett
Absorption Spectra: Solid (PS specific); dashed (all pigments)
ONE DIMENSIONAL MODEL
(Hickman et al, MEPS, 2010)
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
(Data courtesy: M. Zubkov, J. Heywood)
(Hickman et al, MEPS, 2010)
AMT15
Vertical distribution of phytoplankton types
OBSERVATIONS MODEL
ONE DIMENSIONAL MODEL
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
more sophisticated treatment of light stream:
- spectral surface input (OASIM – Watson Gregg)
- radiative transfer code: 3 light streams (Iterative solver Oliver Jahn: following Aas, 1987; Ackelson et al 1994, Gregg and Casey, 2009)
- resolve absorption, scattering and backscattering
NEW DEVELOPMENTS
450 475 500 600 625 650 675
a(λ), b(λ), bb(λ)
525 550 575 700400 425
CDOM
water
aw(λ), bw(λ), bbw(λ)
aCDOM(λ)
ap(λ), bp(λ), bbp(λ)
detritus
ad(λ), bd(λ),bbd(λ)
Phytoplankton:diatomscoccolithophoreslarge Eukaryotespico-eukaryotesSynechococcusProchloroccusTrichodesmium
DEVELOPMENTS: RADIATIVE TRANSFER
In collaboration with Anna Hickman, Oliver Jahn, Watson Gregg
Slide modified from Watson Greggexplicit
explicit, under development
function of Chl
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
NEW DEVELOPMENTS
ADDITIONAL FUNCTONAL TYPES
Absorption data fromL. Moore, D. Suggett
In collaboration with Anna Hickman, Oliver Jahn, Watson Gregg
Scattering data fromGregg+Casey, 2009;Morel et al 1993
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
NEW DEVELOPMENTS
Model Output:
• upwelling radiance• water leaving radiance• backscattering (total, detrital, phytoplankton)• absorption (total, CDOM, phytoplankton)• forward scattering• pigments
450nm
500nm
550nm
UPWELLING RADIANCE: July
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
JULY
log10 phytoplankonbiomass (uMP)
log10 backscatterby phytoplankonsum bphym(1/m)
Coccolithophorefraction biomass
NEW DEVELOPMENTS: PRELIMINARY RESULTS
450nm
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
Remote sensing beginning to resolve aspects ofphytoplankton community and functionality:
e.g. PHYSAT (Alvain et al), PHYTODAS (Bracher et al), Aiken et al, Sathyendranath et al, Balch et al, Hirata et al, Uitz et al, Giotti+Bricaud, Mouw+Yoder, Kostadinov et al, etc
Models also resolving community structure:
By resolving optical properties of model ocean can werelate more to the remotely sensed products?
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
SUMMARY
We are currently working to include radiative transfer code (spectral) and explicit absorption and backscattering.
- will provide a closer link with satellite (and other optical) studies- additional remote sensed products could be used
to validate model- potential for data assimilation- model may then help untangle the mechanisms
leading to variability and trend observed in satellite products
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
MODELS HELP WITH OBS DESIGN
Correlation between model variables
Bennington, McKinley, Dutkiewicz, Ullman; GBC, 2009
- pCO2 well correlated with bloom- but year integrated CO2 Flux is not well
correlated with biological variability in subpolar
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
MODELS HELP WITH OBS DESIGN
Number of years for trend to be visible from natural variability
Henson et al, BG, 2010
- 3 models 2000-2100 A2 scenario- average of about 40 years of continuous and consistent measurements needed
stephanie dutkiewiczhttp://ocean.mit.edu/~stephd
O2
air
sea
Ed Es
(1 - ) (1 - )EdEs
Eu
Ed, Es
Lw
OASIM: Ocean-AtmosphereSpectral Irradiance Model
DEVELOPMENTS: RADIATIVE TRANSFER MODEL
Gregg and Casey, 2009
Ed = direct irradianceEs = diffuse downwellingEu = upwelling radianceρ = surface reflectanceLw = water leaving radiance
CO2 W Vaerosols
O3
Three-Stream Ocean Irradiance Modulefollowing Aas(1987), Ackleson et al (1994), Gregg and Casey (2009)
Oliver Jahn
Iterative solver (repeated down/up integration)
Gregg's truncation (downward integration
only)
Downward decaying modes only (à la Aas)
Iterative solver (repeated down/up
integration)
RADTRANS: approximations
Ed
Es
EuEs
Eu
EdEuEs
Ed
Lw
I
I
Oliver Jahn