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Regulation of seasonal primary production in eastern boundary upwelling systems. Monique Messié & Francisco Chavez Monterey Bay Aquarium Research Institute. Regulation of seasonal primary production in eastern boundary upwelling systems. Monique Messié & Francisco Chavez - PowerPoint PPT Presentation
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Regulation of seasonal primary productionin eastern boundary upwelling systems
Monique Messié & Francisco ChavezMonterey Bay Aquarium Research Institute
Regulation of seasonal primary productionin eastern boundary upwelling systems
Monique Messié & Francisco ChavezMonterey Bay Aquarium Research Institute
nitrate supply (N flux) ↔ potential new production (C flux)
nitrate supply(NO3
-)
regeneration (NH4
+)primary production
regenerated
new
coast
surface
mixed layer depth
150 km
Average primary production vs. potential new production (nitrate supply)
XNitrate supply = nitrate at depth (60m)
1. The N-ratio concept
satellite-derived primary production (Behrenfeld & Falkowski, 1997)
nitrate supply(NO3
-)
regeneration (NH4
+)primary production
regenerated
new
coast
surface
mixed layer depth
wind
coastal transportEkman pumping
150 km
Comparing
primary production
and nitrate supply from satellite winds and in-situ nitrate (Messié et al., 2009)
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(NO3
-)
regeneration (NH4
+)primary production
regenerated
new
coast
surface
mixed layer depth
wind
Ekman pumpingcoastal 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 production
1. N-ratio concept
PP
Seasonal primary production
time
latit
ude
1. N-ratio concept
PP
Seasonal primary production vs. potential new production
time
latit
ude
NPpot
RP
150 km
nitrate supply(NO3
-)
regeneration (NH4
+)
potential RP
potential NP
coast
surface
mixed layer depth
avai
labl
e Nprimary
productionRP
NPphoto-
synthesis
N-remainnon-used nitrate
accumulation
subduction
offshore export
N-ratio
* PP
f-rati
o * P
P
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 productionNP = new production
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, constant
N-ratio = f-ratio +
f-ratio ~ 0.5, constant1. N-ratio concept
N-ratio
Black contours = surface nitrate
N-ratio = f-ratioall nitrate supplied is consumed
nitrate regulating
N-ratio > f-ratioremaining nitrate
other factors regulatingN-ratio = f-ratio +
f-ratios
N-ratios
N-ratio ≤ 0.5 N-ratio ≥ 0.8
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?
?
2. N-ratio analysis
back to the definition of primary production…
PP, physical export, mortality, sinking, grazing
Temperature, species Light, nutrients
growth rate
max growth rate0 ≤ ≤ 1 limitation term𝑷𝑷=𝑏𝑖𝑜𝑚𝑎𝑠𝑠∗𝜇𝑚𝑎𝑥∗𝛾
coast
surface
mixed layer depth
biomass * growth
TemperatureLight
150 km
Physical export
residence time Tbox
wind-driven downwelling
EKE
shelf width Wshelf
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, species
A few words about physical export…
Needs: Tbox ≤ 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 pumpingcoastal transport
150 km
upwelling
Ekman pumping
Dupwell
(Ekman downwelling)
downwelling
A few words about physical export…
Needs: Tbox ≤ 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)
2. N-ratio analysis
Physical export Light IronTbox EKE Ekneg PAR MLD Imean Wshelf dust
California X X XNW Africa X XPeru X X XBenguela 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 IronTbox EKE Ekneg PAR MLD Imean Wshelf dust
California
NW Africa
Peru
Benguela
3. Correlation analysis and PP regulation
Spatial correlations with PP Seasonal cycles
PPN-supplyWshelf / dustlighttemperatureTbox
Example: California
Winter: 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 export
3. Correlation analysis and PP regulationSpatial correlations with PP
Seasonal cycles
Benguela
From N-ratio analysis: high N-ratios = light / export / iron
NW AfricaFrom N-ratio analysis: high N-ratios = iron
High N-ratio narrow shelf
3. PP regulation
high N-ratios
Nitrate supplyIron supplyPhysical exportLight
• 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 supplyIron supplyPhysical exportLight
California Peru NW Africa Benguela
averaged N-ratio 0.73 0.82 0.52 0.63