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Ecological Stoichiometry
Hao WangMATH 570
University of Alberta
What is STOICHIOMETRY?
Stoichiometry in biology: Focuses on the balance of elements and energy within biological systems. This includes metabolism, growth, etc.
Stoichiometry in ecology: Focuses on the balance of elements and energy within ecological systems. This includes competition, commensalisms, etc.
Stoichiometry in chemistry: Focuses on the balance of elements within chemical equations.
Why need STOICHIOMETRY?Carbon (C), nitrogen (N), and phosphorus (P) are vital constitutes in biomass: C supplies energy to cells, N is essential to build proteins, and P is an essential component of nucleic acids. The scarcity of any of these elements canSeverely restrict organism and population growth.
What would happen to cows if there wasn't so much sunlight?
Expectations from a 9-year old ecologist
James J. Elser’sson
What would happen to secondary production if solar radiation were reduced?
Expectations from single-currency ecological theory
Solar RadiationHighLow
Sec
on
dar
y P
rod
uct
ion
,H
erb
ivo
re B
iom
ass
Solar Radiation
Pri
mar
y P
rod
uct
ion
,A
uto
tro
ph
Bio
mas
s
HighLow
Terrestrial herbivore (Pieris)Freshwater herbivore (Daphnia)
0
10
20
30
40
50
60
10% 90%
0 200 400 600 800 1000
Biomass C:P in Food
mean
Daphnia magna
0
5
10
15
20
25
0 10 20 30 40Biomass C:N in Food
10%
mean90% (59)Pieris rapae
From: Elser, J.J., W.F. Fagan, R.F. Denno, D.R. Dobberfuhl, A. Folarin, A. Huberty, S. Interlandi, S.S. Kilham, E. McCauley, K.L. Schulz, E.H. Siemann, and R.W. Sterner. 2000. Nutritional constraints in terrestrial and freshwater food webs. Nature 408: 578-580.
Stoichiometric Imbalance Impairs HerbivoresIn Freshwater and Terrestrial Ecosystems
Mass of New Biomass ProducedGGE(gross growth efficiency)=
Mass Ingested
Solar RadiationHighLow
Sec
on
dar
y P
rod
uct
ion
,H
erb
ivo
re B
iom
ass
Very High
Starvation Junk food
(CXN
YP
Z)
prey + (C
XN
YP
Z)
predator -> Q (C
XN
YP
Z)
predator + (C
XN
YP
Z)’
waste
From: Elser, J.J., and J. Urabe. 1999. The stoichiometry of consumer-driven nutrient recycling: theory, observations, and consequences. Ecology 80: 735-751.
(CXN
YP
Z)inorganic
+ (CXN
YP
Z)
autotroph + light -> Q (C
XN
YP
Z)'
autotroph + (C
XN
YP
Z)’ inorganic
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
PCC
C CCC
CC
C
C
C C
CCC
CC
C
C
CCC
C CC
C
C CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
P C
C
CC
CCC
C CPC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
CC
C
C
C P
CCC
CC
C
C
PCC
C CC
C
C
CC
C
C C
C
C
C
P
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
P
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCP
C CCC
C
CC
C
C C
CCC
CC
C
C
CPC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CCC
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
CC
C
C
C C
CCC
CC C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C CP
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
100C : 1P
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
CC
C
C
C C
CCC
CC
C
C
CCC
C CC
C
C CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
CC
C
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CCC
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C
CC
C
CC
C
C
C C
C
CC
CCC
C CPC
CC
C
C
C C
CCC
CC C
C
CCC
C CC
C
C
CC
C
C C
C
C
C
C
C CC
C
CC
C
C
C C
C
CC
CCC
C CCC
C
CC
C
C C
CCC
CC
1000C : 1P
C, N, and P are three of the main constitutes in biological structural molecules. HOWEVER, C,N, and P are not particularly abundant on Earth or in the universe as a whole and thus it seems that living things made a very discriminating selection of elements from the environment.
S0.11
S0.14
C0.18
C20.2
Ca3.22
Ca2.5
Fe4.18
Fe0.01
Si25.80
O50.02
O63.0
Al7.30
Na2.36
Na0.10
K2.28
K0.11
H0.25
H9.9
P0.11
P1.14
N0.03
N2.5
Composition of Earth’s Crust
Composition of Human Body
Laws and Hypotheses
• Conservation Law of Matter
• Homeostasis
• Liebig’s Minimum Law
• Growth Rate Hypothesis
• Light:Nutrient Hypothesis
Conservation Law of Matter
In an ordinary chemical reaction, matter
and component elements are neither
created nor destroyed.
Homeostasis
Consumers have fixed elemental composition in biomass. This is often called “strict homeostasis”. However, plants have highly variable nutrient contents because of physiological plasticity in relation to environmental conditions such as light, nutrient supply, CO2, etc.
(examined via bifurcations in Hao Wang, Robert W. Sterner, and James J. Elser. On the "strict homeostasis" assumption in ecological stoichiometry, Ecological Modelling, Vol. 243: 81-88, 2012).
[Strict] Homeostasis (animals, heterotrophic bacteria, etc.)
Nonhomeostasis (plants, etc.)
Producer C:nutrient
Her
bivo
re C
:nut
rient
0
Substrate C:nutrient
Pro
duce
r C
:nut
rient
0
Droop Equation
Plant growth rate as
a function of cell
quota (P:C or N:C
ratio) is modeled and
experimentally
verified by Michael
Droop in 1973-1974.max min/ (1 / ) ,
where A is the plant biomass,
is the cell quota.
dA dt Q Q A
Q
Liebig’s Minimum Law
The growth of an organism is controlled
by the most limiting element.
min, min, min,
The specific biomass growth rate
min(1 ,1 ,1 )P N C
P N C
Q Q Q
Q Q Q
From: C.A. Klausmeier et al. 2004. Optimal nitrogen-to-phosphorus stoichiometry of phytoplankton. Nature.
Growth Rate Hypothesis
Rapid growth requires
increased allocation to
P-rich ribosomal RNA
to meet the protein
synthesis demands of
rapid growth.
Based on: Elser, J.J., D.R. Dobberfuhl, N.A. MacKay, and J.H. Schampel. Organism size, life history, and N:P stoichiometry: toward a unified view of cellular and ecosystem processes. BioScience 46: 674-684.
Body C:N:P
food quality constraints on growth /
reproduction
resource competition
trophic efficiency
nutrient recycling
natural selection on growth rate
cellular investment (ribosome content)
biochemical investment (RNA:protein)
Autotroph C : Nutrient Ratio Increases(Nutrient Content Declines)
With Increasing Light Intensity
From: Sterner, R.W. and J.J. Elser . 2002. Ecological Stoichiometry: The Biology of Elements from Molecules to the Biosphere. Princeton University Press, Princeton, NJ.
N:C
(µ
g :
mg
)P
:C
(µg
: m
g)
N:P
(µ
g :
µg
)
(no relationships)
300
200
100
030
20
12840
0 0.4 0.8 1.2
Specific Growth Rate (d )-1
N-limited GrowthC
ellu
lar
Ra
tio
s (
by
ma
ss
)
P:C
(µ
g :
mg
)N
:C
(µg
: m
g)
N:P
(µ
g :
µg
)15
10
5
300
200
10050
30
increasing light
P-limited Growth
Specific Growth Rate (d )-1
0 0.4 0.8 1.2
0.0
0.1
0.2
0.3
0.4
High LowLight
% P a
ba
ab
a aa
a
% N a
abb b
aba
bb
0.0
1.0
2.0
3.0
4.0
High LowLight
HN / HP
LN / LP
HN / LPLN / HP
Nutrient-limitedCyanobacterium(Synechococcus linearis)
From Healey (1985)
Nutrient-limitedRed pine(Pinus resinosa)
From Elliot and White (1994)
Light:Nutrient Hypothesis
Aquatic ecosystems with low
light:nutrient ratios should have several
trophic levels simultaneously carbon
(or energy) limited, while ecosystems
with high light:nutrient ratios should
have several trophic levels
simultaneously limited by nutrients.
Evaluating The Light:Nutrient Hypothesis:A Mix of Strategies
SimpleControlledReplicatedShortSmallArtificial
ComplexUncontrolledUnreplicated
LongLarge
Natural
Analytical model
Simulationmodel
Labflask
Small indoormicrocosms
Fieldmicrocosms
Whole-ecosystemmanipulation
Fieldsampling
Big indoormicrocosms
Theoretical Test of Light:Nutrient Effects
Model of Loladze, Kuang and Elser (modified from model of T. Andersen)
Producer
Grazer
x' (t) = bx (1 - min[K, (P - y)/ q]
x ) - f (x)y
y' (t) = min (1,
(P - y) / x ) f (x)y - dy
From: Loladze, I, Y. Kuang, and J.J. Elser. 2000. Stoichiometry in producer-grazer systems: linking energy flow and element cycling. Bull. Math. Biol. 62: 1137-1162.
(carbon biomass)
'( ) (1 ) ( )min[ , ( ) / ]
( ) /'( ) min(1, ) ( )
'( ) min(1 ,1 ) ( )( ) /
( ) /'( ) min(1, ) ( )
'( ) min(1 ,1 ) ( )( ) /
( ) /'( ) min(1, ) ( )
xx t bx f x y
K P y q
P y xy t f x y dy
x xx t bx f x y
K P y q
P y xy t f x y dy
x qx t bx f x y
K P y x
P y xy t f x y dy
Logistic growth (light-dependent)
Droop equation (nutrient-dependent)
Plant P:C ratio
Herbivore P:C ratio
Assumption 1Fixed total mass of phosphorus, P, in the entire system.
Assumption 2Plant P:C varies with a minimum q; herbivore P:C is a constant, θ.
Assumption 3All phosphorus of the system is either in plants or in herbivores.
Liebig’s Law
light
light
light
Model of Loladze, Kuang and Elser (modified from model of T. Andersen)
From: Loladze, I, Y. Kuang, and J.J. Elser. 2000. Stoichiometry in producer-grazer systems: linking energy flow and element cycling. Bull. Math. Biol. 62: 1137-1162.
Theoretical Test of Light:Nutrient Effects
Model of Loladze, Kuang and Elser (modified from model of T. Andersen)
light
Theoretical Test of Light:Nutrient Effects
Grazer
From: Loladze, I, Y. Kuang, and J.J. Elser. 2000. Stoichiometry in producer-grazer systems: linking energy flow and element cycling. Bull. Math. Biol. 62: 1137-1162.
Experimental Test of the Light:Nutrient Hypothesis
"Aquatron" Experiment (summer 2000) by Urabe and Elser
Aquatron Dynamics
0
0.5
1
1.5
Co
nsu
me
r b
iom
ass
(m
gC
l-1)
0 30 60 90
A
0
2
4
6
Fo
od
bio
ma
ss (
mg
C l-1
) P:C
ratio
of fo
od
(x 10 -3)
0 30 60 90
B
0 30 60 90
C
Days
1
10
50
5
Low Light(40 µE / sq m / s)
High Light (310 µE / sq m / s)
(Extra)High Light
(380 µE / sq m / s)
AlgalP:C
Algal C
Daphnia
C transferefficiency:
~30%
C transferefficiency:
~7%
Urabe, J., J.J. Elser, M. Kyle, T. Sekino and Z. Kawabata. 2002. Herbivorous animals can mitigate unfavorable ratios of energy and material supplies by enhancing nutrient recycling. Ecology Letters: in press.
Daphnia
Algal C
Algal C
Daphnia
Extinction?
100 % treatment 25 % treatment
The Light : Nutrient Project
Field Test of the Light:Nutrient Hypothesis
The Light:Nutrient Hypothesis:Consequences
low high
I : nutrient supplym
low high
Particulate C:P
lowhigh
"Ecological efficiency" (2°/1°)
weak strong
Phytoplankton-bacteria competition
strong weak
Strength of trophic cascade
high low
Efficiency of P recycling
Based on: Sterner, R.W., J.J. Elser, E.J. Fee, S.J. Guildford, and T.H. Chrzanowski. 1997. The light:nutrient balance in lakes: the balance of energy and materials affects ecosystem structure and process. Am. Nat. 150: 663-684.
Under future climate scenarios in the continental boreal regions (Schindler 1998), runoff to lakes will likely decrease. Effects of such shifts on lakes remain unclear.
However, such climate changes will likely lower external nutrient supply while simultaneously raising light intensity (due to lower DOC inputs). Light:nutrient supply may become increasingly unbalanced.
These effects are analogous to effects of elevated pCO2 in terrestrial systems and appear to be driven by similar mechanisms.
Light:Nutrient Balance and Global Change
Daphnia-Algae Experiment
Study organisms
Daphnia pulex: a widespread and important planktonic herbivore in N. America
Daphnia lumholtzi: a daphnia native to Africa but now invasive in N. America.
Scenedesmus obliquus: a Chlorophyte (green algae) found in many lakes and easily grown in the laboratory.
Pictures courtesy of: Paul Hebert; aslo.org; and www.biol.tsukuba.ac.jp/
Methods
Population sizes and species composition were measured twice weekly, while algal carbon and phosphorus data and Daphnia body sizes and egg numbers were measured once weekly.
Experimental Design High Light Low Light
Daphnia pulex alone
Daphnia lumholtzi alone
No Daphnia
D. pulex and D. lumholtzi together
n = 3
n = 3n = 3
n = 3n = 3
n = 3n = 3
n = 3
3-L Jars 218 uE/m2/s21.8 uE/m2/s
Hi gh Li ght - Compet i t i on
0%
20%
40%
60%
80%
100%
1 2 3 4 5 6 7 8 9 10 11 12 13
Ti me (hal f week)
Percentage
Lumhol tziPul ex
Low Li ght - Competi ti on
0%
20%
40%
60%
80%
100%
1 2 3 4 5 6 7 8 9 10 11 12 13
Ti me (hal f week)
Percentage
Lumhol tziPul ex
Main Experimental Results
Competitive Exclusion in both high light or low light!
Competition Model
1 1 2 2
11 1 1 1 1
1
22 2 2 2 2
2
1 1 2 2 1 1
1 ( ) ( )min{ , / }
/ ˆˆ min 1, ( ) (D. pulex)
/ ˆˆ min 1, ( ) (D. lumholtzi)
( ) ( )
dx xrx f x y f x y
dt K p q
dy p xe f x y d y
dt
dy p xe f x y d y
dt
dp pg T p y y x f x y
dt x
2 2( )p
f x y dpx
Algal C
Algal P
Pulex C
Lumholtzi C
High Light Low Lightmeasured in carbon biomass
HypothesisD. lumholtzi has higher requirements for C (energy)
while D. pulex has higher requirements for P (nutrient).
Rich Dynamics
Low light intensityin the experiment
High light intensityin the experiment
A chaotic attractor
The Light:Nutrient Hypothesis:Consequences
low high
I : nutrient supplym
low high
Particulate C:P
lowhigh
"Ecological efficiency" (2°/1°)
weak strong
Phytoplankton-bacteria competition
strong weak
Strength of trophic cascade
high low
Efficiency of P recycling
Based on: Sterner, R.W., J.J. Elser, E.J. Fee, S.J. Guildford, and T.H. Chrzanowski. 1997. The light:nutrient balance in lakes: the balance of energy and materials affects ecosystem structure and process. Am. Nat. 150: 663-684.
Dynamics of Stoichiometric Bacteria-Algae Interactions in the Epilimnion
Question 1
What is the relationship between cyanobacteria and algae?
How do light and nutrient availability regulate relative abundances of bacteria and algae in the Epilimnion?
A Lake System
mz quickly well mixed
input
water exchange
Epilimnion
Hypolimnion
quiescent
brookriver
input input
Scenario The Epilimnion is quickly well mixed in the sense that it is well mixed over night.
Assumption The Epilimnion is well mixed all the time.
Algae Competitive System
0
0
0
1 ( , )1
( , )
1 ( , )( , ) 1 (3.1)
( , )
( ) ( , )
where
( , ) exp[ ( ) ]
( , ) 1
( , )
m
m
m
zm
A mm m
zm
Am
inm
in bg
z
QdA I s A DA ds l A A
dt Q z I s A H z
QdQ I s AQ P Q ds
dt Q z I s A H
dP DP P Q P A
dt z
I s A I kA K s
I s Ads
I s A H kA K
max
ln( , )
( , )
in
bg m
M
M m
H I
H I z A
Q Q PQ P
Q Q M P
This system is modeled for Epilimnion following‘quickly well mixed’.
Algae
Cell Quota
DIP Flexible stoichiometry of algae using Droop’s
form as a nutrient limitng factor
Average sunlight uptake efficiency
of algae in the mixing layer
Respiration loss
Algal sinking and water exchangePhosphorus input
and water exchange
Phosphorus consumption
by algae
The replenishment rate of cell quota is the per unit consumption rate
The cell quota depletion rate is proportional to
algal growth rate
Hao Wang, Hal L. Smith, Yang Kuang, and James J. Elser. 2007. Dynamics of Stoichiometric Bacteria-Algae Interactions in the Epilimnion. SIAM J. Appl. Math, Vol. 68, pp. 503-522.
. , whenever (0) .
. ( ), ( ) 0, whenever (0), (0) 0 .
. Let , which is the total phosphorus of the
system (3.1), then limsup ( ) .
In conclusion,
m M m M
int
Q Q Q Q Q Q
A t P t A P
S AQ P
S t P
Result 1
Result 2
Result 3
we show the boundedness of the system.
Rationality of Model
Exercise 30: Prove these results mathematically to obtain a forward invariant set
0
0
0
. The basic reproductive number for algae is
(0)(1 / )
1 ( , )where ( ) .
( , )
ˆThen the algae extinction steady state E (0, , ) is
(1) locally asymptotical
m
m
A m
Dm z
z
m
in
h Q QR
l
I s Ah A ds
z I s A H
Q P
Local Stability
0
0
ly stable when 1;
(2) unstable when 1.
R
R
0 0
0
*
. 1 implies E is globally asymptotically
stable. 1 implies there exists a unique positive steady
state E and algae uniformly persist: there exists 0 such
that liminf ( )t
R
R
A t
Global Stability
for all solutions with (0) 0.
Proof: Apply theory of monotone dynamical systems
to prove the global stability.
A
P
A Q
+
+
_
competitive system
System Types of Two Species
• Predator-prey
• Cooperative
• Competitive
The latter two are called monotonedynamical systems.How about the three species case? Hal Smith’s TMDS book
+
-Species 2Species 1
+Species 2Species 1
+
-Species 2Species 1
-
Algae love shallower epilimnions, becausesunlight is more sufficient on average.
A-B story
DIP
DOC
Competition
Stimulation
Sunlight
P input
Scenario Algae have flexible stoichiometry whereas bacteria have relatively fixed stoichiometry.
Assumption (P:C) in bacterial cells is fixed.W. Makino, J. B. Cotner, R. W. Sterner and J. J. Elser, Are bacteria more like plants or animals? Growth rate and resource dependence of bacterial C:N:P stoichiometry, Functional Ecology, 17 (2003), pp. 121-130.
Homeostasis
DOC Exudation by Algae
total OCproduced
OC used foralgal growth
extra OCexuded from algae
Energy
0
The exudation rate of DOC by algae is the difference
between the potential growth rate attained when
growth is not mineral nutrient limited,
1 ( , ) , and actual growth rate,
( , )
1
mz
Am
mA
I s AA ds
z I s A H
QA
Q
0
0
1 ( , ) .
( , )
Therefore, the exudation rate is
1 ( , ) .
( , )
m
m
z
m
zm
Am
I s Ads
z I s A H
Q I s AA ds
Q z I s A H
Algae-Bacteria System
0
0
1 ( , )1
( , )
1 ( , )( , ) 1
( , )
( ) ( , ) ( ) ( ) (2.2)
( ) ( ) ( )
m
m
zm
A mm m
zm
Am
in Bm
B r gm
mA
QdA I s A DA ds l A A
dt Q z I s A H z
QdQ I s AQ P Q ds
dt Q z I s A H
dP DP P Q P A Bf P g C
dt z
dB DBf P g C B B
dt z
QdCA
dt Q
0
1 ( , )( ) ( )
( , )
mzB
m m
I s A Dds Bf P g C C
z I s A H r z
Consumptionsby bacteria
Bacterial growthRespiration and grazing
Water exchange
Exudationby Algae
*1
The basic reproductive number for bacteria is
( ) ( ), where , are components of E
in the system (3.1). This is calculated from the linear
approximation (Jacobian matrix).
m
B
Dr g z
f P g CR P C
Result 1.
R
A
Positivity and Dissipativity (or boundedness).
When (0) , both algae and bacteria go extinct.m
Dh
z
esult 2.
Result 3.
Data fitting
(c)(f) are from 1999 ponds experiment, Roberts and Howarth, Limnol. Oceanogr., 2006
Balance of light and nutrient availability
Bacterial Strains
• LNA: bacterial strain with low nucleic acid contents.
• HNA: bacterial strain with high nucleic acid contents.
• VHNA: bacterial strain with very high nucleic acid contents.
Body C:N:P
food quality constraints on growth /
reproduction
resource competition
trophic efficiency
nutrient recycling
natural selection on growth rate
cellular investment (ribosome content)
biochemical investment (RNA:protein)
(Nishimura et al 2005)
thermocline
Epilimnion
Hypolimnion
(Nishimura et al 2005, Applied and Environmental Microbiology)
VHNA + HNA vs LNA
Previous claim LNA is less active, or dormant.
Observation In late August of Lake Biwa, LNA grows faster than VHNA and HNA.
Hypothesis Probably P-limitation is severe at that time and LNA has higher nutrient uptake efficiency or lower requirements for P.
Question 2
Why do LNA bacteria dominate other two strainsin late August of Lake Biwa?
Competing Bacterial Strains
0
0
1 1 1 1 2 2 2 2
11 1 1 1 1
22 2
1 ( , )1
( , )
1 ( , )( , ) 1
( , )
( ) ( , ) [ ( ) ( )] ( )
( ) ( ) ( )
m
m
zm
A mm m
zm
Am
inm
r gm
QdA I s A DA ds l A A
dt Q z I s A H z
QdQ I s AQ P Q ds
dt Q z I s A H
dP DP P Q P A B f P B f P g C
dt z
dB DB f P g C B B
dt z
dBB
dt
2 2 2
1 1 1 2 2 20
( ) ( ) ( )
1 ( , ) 1[ ( ) ( )] ( )
( , )
m
r gm
zm
Am m
Df P g C B B
z
QdC I s A DA ds B f P B f P g C C
dt Q z I s A H r z
HNA
LNA
(Nishimura et al 2005, Applied and Environmental Microbiology)
VHNA + HNA vs LNA
Previous claim LNA is less active, or dormant.
Observation In late August of Lake Biwa, LNA grows faster than VHNA and HNA.
Hypothesis Probably P-limitation is severe at that time and LNA has higher nutrient uptake efficiency or lower requirements for P.
Hypothesis 1“higher nutrient uptake efficiency” “lower half-saturation constant for P”
Hypothesis 2“lower requirements for P” “smaller cell quota”
Hypothesis 2Hypothesis 2 Hypothesis 1Hypothesis 1
Lower P requirement higher uptake efficiency
Both of those seemingly conflict views can be true under different nutrient status.
Stoichiometry Discussion
Mathematics inside ES
…
…
Xiong Li, Hao Wang, Yang Kuang,J. Math. Biol. (2011) DOI 10.1007/s00285-010-0392-2
C, N, and P are three of the main constitutes in biological structural molecules. HOWEVER, C,N, and P are not particularly abundant on Earth or in the universe as a whole and thus it seems that living things made a very discriminating selection of elements from the environment.
S0.11
S0.14
C0.18
C20.2
Ca3.22
Ca2.5
Fe4.18
Fe0.01
Si25.80
O50.02
O63.0
Al7.30
Na2.36
Na0.10
K2.28
K0.11
H0.25
H9.9
P0.11
P1.14
N0.03
N2.5
Composition of Earth’s Crust
Composition of Human Body
Significant concentrations of C and N in Earth’s atmosphere?
What features of C, N, and P are so important for biological functionthat these elements have been so intensively distilled from the nonliving world?
C and Si are in the same column of the periodic table, and are almostequally abundant in the solar system, and Si is even more abundantthan C in the Earth’s crust. Why C, not Si to form living things?(Possible answers: C has very high binding energy store energy; high degree of bonding flexibility of C considerable architecturalflexibility)
Why N, P as main nutrient elements, not other elements?
A chemostat-type stoichiometric model
organism
Rin D
R
Q
min
min
( )
( ) (1 )
(1 )
in
dRR DR f R A
dtQdQ
f R rQdt Q
QdArA DA
dt Q
Exercise 31:Interpret this model term byterm and performstability analysis,and discuss viasimulations howRin and D affectthe dynamics