mmi meeting, march 2013 mick follows how do ocean ecosystem models work? applications and links to...
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MMI meeting, March 2013Mick Follows
How do ocean ecosystem models work?
Applications and links to ‘omics-based observations
Physiological sub-models
Observed seasonal variation of phytoplankton at Georges Bank
G. Riley, J. Marine Res. 6, 54-73 (1946)
Phyto
pla
nkt
on,
B
J F M A M J J A S O N D month
Riley’s mechanistic model
Rate of growth respiration grazingchange
B = phytoplankton biomass (mol C m-3)Z = zooplankton biomass (mol C m-3)μ= growth rate (s-1)K = respiration rate (s-1)g = grazing rate (s-1 (mol C m-3)-1)
Riley’s mechanistic model
growth respiration grazing
J F M A M J J A S O N D
Phyto
pla
nkt
on,
B
theoretical curve observed
Extending Riley’s model
Monod and Droop kinetics
NPZ-type modelse.g. Steele (1958)
N
P
Z
μ
Kr
gPhytoplankton
Nutrient Zooplankton
Multiple resources, diverse populations
P
N
P
Z
D
N1 N2
Functional group models – multiple phytoplankton types
e.g. Chai et al (2002), Moore et al (2002)
Remotely sensed chlorophyll NASA MODIS
Ocean model
MOVIE – removed for compactness
Comparison of remotely sensed and simluated surface ocean chlorophyll
Genomic mapping of ecotypes with known physiologies
Prochloroccocus
Data Johnson et al (2006); model Follows et al (2007)
Mapping of abundance of specific functional types
Data Church et al (2008), model Monteiro et al (2010)
Trade-offs define biogeography
Trade-offs for diazotrophynot dependent on fixed nitrogen
high iron quota
slow maximum growth rate
Ocean model Fanny Monteiro
InterpretationResource ratio perspective (Tilman, 1982)
Relative rates of delivery of N, P, Fe define range of diazotrophs (Ward et al, 2013; submitted)
Physiological models
For biogeochemical modeling purposes we would like:
Flexible and prognostic elemental ratios
Mechanistic understanding/parameterizations of population growth rates
Relatively few state variables for computational tractability
1940s 1960s 1970s 2000sMonod/ Droop/Caperon Shuter, McCarty MetabolicRedfield Internal stores Macro-molecular reconstruction, FBA
Flexible elemental ratiosFew state variablesGeneralized framework for heterotrophs/phototrophs
fixed elementalRatios, 1 state variable
Prognostic elemental ratios (Ecological Stoichiometry)
Must be backwards compatible
Model of Azotobacter Vinelandii• Nitrogen fixing soil bacteria• Conserve internal fluxes of
mass, electrons and energy• McCarty (1965), Vallino
et al (1996) …• Biophysical model of
substrate and O2 uptake• Pasciak and Gavis
(1974), Staal et al (2003), …
• Demand intra-cellular O2 ~ 0
Keisuke Inomura
pyruvate
“biomass”
sucroseNH4+
O2
CO2
O2
CO2
N2
C5H7O2N
Moleculardiffusion
Laboratory data: continuous cultureKuhle and Oetze (1988) Model (Keisuke Inomura)
[O2]
Low yields in oxygenated medium Slow growth rates if substrate limited
Genome-scale metabolic reconstructions and Flux Balance
Analysis
e.g. Palsson, Systems Biology, (2006)