in eastern boundary upwelling systems Monique Messié amp Francisco Chavez Monterey Bay Aquarium Research Institute Regulation of seasonal primary production in eastern boundary upwelling systems ID: 384509
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Slide1
Regulation of seasonal primary productionin eastern boundary upwelling systems
Monique Messié & Francisco ChavezMonterey Bay Aquarium Research InstituteSlide2
Regulation of seasonal primary productionin eastern boundary upwelling systems
Monique Messié & Francisco ChavezMonterey Bay Aquarium Research
Institute
n
itrate
supply
(N flux) ↔ potential new production (C flux)
nitrate
supply
(NO
3
-
)
regeneration
(NH4+)
primary production
regenerated
new
coast
surface
mixed layer depth
150 kmSlide3
Average
primary production
vs.
potential new production
(nitrate supply)Slide4
X
Nitrate
supply
=
nitrate
at
depth
(60m)1. The N-ratio concept
satellite-derived primary production (Behrenfeld & Falkowski, 1997)
nitrate
supply
(NO
3
-
)
regeneration
(NH
4
+
)
p
rimary
production
regenerated
new
coast
surface
mixed layer
depth
wind
coastal
transport
Ekman
pumping
150 km
Comparing
primary production
and
nitrate suppl
y
from satellite winds and in-situ nitrate
(Messié et al., 2009)Slide5
1.
The N-ratio concept
carbon-equivalent of nitrate supply assuming C:N = 106:16
(Messié et al., 2006)
satellite-derived primary production
(
Behrenfeld & Falkowski, 1997)
nitrate
supply
(NO
3
-
)
regeneration
(NH4+
)primary production
regenerated
new
coast
surface
mixed layer depth
wind
Ekman
pumping
coastal
transport
nitrate
at
depth
(60m)
X
150 km
Nitrate
supply
=
Potential new production
= new production that would be achieved if all nitrate supplied was consumed
Comparing
primary
production
and
potential
new
productionSlide6
1.
N-ratio concept
PP
Seasonal
primary production
time
latitudeSlide7
1.
N-ratio concept
PP
Seasonal
primary production
vs.
potential new production
time
latitude
NP
potSlide8
RP
150 km
nitrate
supply
(NO
3
-
)
regeneration
(NH
4
+
)
potential
RPpotential NPcoastsurface
mixed layer depth
available
N
p
rimary
production
RP
NP
photo-
synthesis
N-
remain
non-
used
nitrate
accumulation
subduction
offshore export
N-ratio
* PP
f-ratio
* PP
N-ratio =
1.
N-ratio concept
N-ratio = f-ratio
if
all nitrate
supplied
is
consumed
f-ratio =
(
Eppley
& Peterson, 1979)
N-ratio =
f-ratio
+
RP =
regenerated
production
NP = new productionSlide9
N-ratio =
1.
N-ratio concept
f-ratios
(
Laws
et al. 2000;
Dunne et al., 2005)N-ratios(Eppley & Peterson, 1979)
f-ratio =
(Eppley & Peterson, 1979) f-ratio ~ 0.5
, constantN-ratio = f-ratio +
Slide10
f-ratio ~
0.5, constant
1.
N-ratio concept
N-ratio
Black contours = surface nitrate
N-ratio = f-ratio
all nitrate supplied is consumed
nitrate regulatingN-ratio > f-ratioremaining nitrateother factors regulating
N-ratio = f-ratio +
f-ratiosN-ratios
N-ratio ≤ 0.5 N-ratio ≥ 0.8Slide11
Nitrate regulation
N-ratio ≤ 0.5
nitrate regulates PP (N-remain ~ 0)
N-ratio
2.
The N-ratio analysis:
nitrate vs. other factors
N-ratio ≤ 0.5
nitrate regulates PP (N-remain ~ 0) N-ratio ≥ 0.8 other factors regulate PP (N-remain > 0)
??
??PP lower than expected from N-supply WHY??Slide12
2
. N-ratio analysis
back to the definition of primary
production
…
PP, physical export,
mortality, sinking, grazingTemperature,
speciesLight, nutrients
growth ratemax growth rate0 ≤ ≤ 1 limitation term
coast
surface
mixed layer
depth
biomass
*
growth
Temperature
Light
150 km
Physical
export
residence time
T
box
wind-driven
downwelling
EKE
shelf width
W
shelf
Iron
supply
dust deposition, river runoff
(Johnson et al., 1999)
(Chase et al., 2007)
Data sources:
QuikSCAT
winds, ETOPO2 bathymetry
, modeled dust from
Mahowald
et al. (2003
), SST Reynolds,
SeaWiFS
PAR, AVISO sea level anomalies
Nitrate
supply
(Messié et al., 2006)
PP,
physical export
,
mortality, sinking, grazing
Light
, nutrients
(
nitrate
,
iron
)
(
nitrate
)
Temperature
,
speciesSlide13
A few words about physical export
…Needs:
T
box
≤ 8 days (Zimmerman et al., 1987; Wilkerson et al., 2006) a mechanism to subduct within the box: EKE
(increases offshore & vertical export of biomass & nutrients, Lathuilière et al., 2010; Gruber et al., 2011) and/or Ekman downwelling
only observed when computing
Tbox up to Dupwell
coast
surface
mixed layer
depth
wind
Ekman
pumping
coastal
transport
150 km
upwelling
Ekman
pumping
D
upwell
(Ekman
downwelling
)
downwellingSlide14
A few words about physical export
…
Needs:
T
box
≤ 8 days (Zimmerman et al., 1987; Wilkerson et al., 2006) a mechanism to subduct within the box: EKE
and/or Ekman downwelling
only observed when computing Tbox up to Dupwell
+ isopycnal advection, mixing & frontal convergence possible (Washburn et al., 1991; Bograd & Mantyla, 2005)Slide15
2
. N-ratio analysis
Physical export
Light
Iron
T
box
EKE
Ek
neg
PARMLDImean
WshelfdustCaliforniaX
XX
NW Africa
XXPeruX
XX
Benguela
X
X
X
X
X
What explains the high N-ratios?
Based on correlations w/ N-ratio, mean value in high N-ratios situations, difference in high vs. low N-ratio situations
Iron regulation off NW Africa?
No iron regulation off Peru?
What about
Benguela
?
Physical export
Light
Iron
T
box
EKE
Ek
neg
PAR
MLD
I
mean
W
shelf
dust
California
NW
Africa
Peru
BenguelaSlide16
3. Correlation analysis and PP regulation
Spatial correlations with PP
Seasonal cycles
PP
N-supply
W
shelf
/ dust
lighttemperatureTbox
Example: CaliforniaWinter: nitrate, light, temperature (Kudela and Dugdale, 2000)Spring: upwelling resumes, physical export
(Bograd and Mantyla, 2005; Gruber et al., 2011)Late summer: iron regulation (Johnson et al., 2001; Elrod et al., 2008)
From N-ratio analysis: high N-ratios =
physical exportSlide17
3. Correlation analysis and PP regulation
Spatial correlations with PP
Seasonal cycles
Benguela
From N-ratio analysis:
high N-ratios =
light
/
export / iron
NW Africa
From N-ratio analysis: high N-ratios = iron
High N-ratio narrow shelfSlide18
3. PP regulation
high N-ratios
Nitrate supply
Iron supply
Physical export
LightSlide19
N-ratio as a tool to monitor nitrate regulation but also ecosystem efficiency
PP regulation highly variable in space and time, concept of co-limitations
Need for validation of iron limitation (NW Africa /
Benguela
)
Conclusions
Nitrate supply
Iron supply
Physical export
LightCalifornia
PeruNW AfricaBenguelaaveraged N-ratio0.730.820.520.63