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Biological Production Rates in the Southern California Current System

David MunroUniversity of Washington

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Acknowledgements Paul Quay, Mark Haught, Johnny

Stutsman, and Jackie Leung (UW) Laurie Juranek, Cynthia Peacock

(NOAA), Deirdre Lockwood, Hilary Palevsky

Ralf Goericke, Dave Wolgast, and CalCOFI research associates (SIO)

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Acknowledgements Funding sources

First year graduate fellowship from the Program on Climate Change

Office of Naval Research (NDSEG) fellowship

NASA WA space grant fellowship National Science Foundation support

for sample supplies and analysis

Primary Production and Carbon Export in the

Coastal Ocean Global aquatic PP from satellites ~45-50

Pg C y-1 (Carr et al., 2006) Based on derived Chl a, PAR, SST, and calibrated with

14C PP Estimates vary by a factor of 2 (Campbell et al., 2002;

Carr et al. 2006) ~20% of ocean PP occurs in continental

margins (50-2000 m depth) (Carr et al., 2002; Muller-Karger et al., 2005)

40 to 50% of global C export flux occurs in continental margins (Muller-Karger et al., 2005; Dunne et al. 2007)

Eastern Boundary Currents (EBC’s) <1% of ocean surface area but ~20% of global fish catch

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Sea surface chlorophyll

From Sarmiento and Gruber

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Net Primary Production

From Sarmiento and Gruber

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Air-Sea C Flux in the Coastal Ocean

Globally, coastal seas may be a small net sink, high variability -0.22±0.16 Pg

C y-1 (Cai et al. 2006)

Global ocean ~ -2.0 Pg C y-1

High variability, many poorly characterized systems

Table 1 and Fig. from Cai et al. 2006

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Productivity terms GOP – Gross O2 production; photosynthetic O2

production via water-splitting reactions in PSII NCP – Net community production; net production

of O2 or C in surface ocean after demands of autotrophic and heterotrophic communities have been met

NPP – Net primary production (Gross C production minus respiration by phytoplankton) Estimated using 14C-PP and VGPM

NCP/GOP ratio – An estimate of the fraction of gross production available for export in terms of O2.

NCP/NPP – equivalent to e-ratio or ef-ratio; fraction of NPP in C terms available for export

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Study Goals I: Spatial and seasonal variability

of PP rates Determine variability of PP and NCP and its impact on coastal C system using in situ methods Gross oxygen production (GOP)

using 17Δ of dissolved O2 Net community production (NCP)

NOP = GOP – (Community Resp) using (O2/Ar)measured

Export efficiency (NOP/GOP) Comparison to incubation-based 14C-PP Validation of satellite-based PP in the

coastal ocean

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Study Goals II: Variability in C export over the last

three decades Estimate NCP using four different

approaches Mixed layer O2 budget Mixed layer nitrate budget 15N uptake f-ratios combined with 14C-

PP Satellite-based (VGPM) x export

algorithms Dunne et al. (2007); Laws et al. (2000)

O2-NCP from biological O2 saturation based on O2/Ar measurements

Evaluate interannual and decadal variability in NCP

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Study Site: CalCOFI

Annual Mean Surface Chl a in mg m-3 from Photobiology Group (SIO)

CalCOFI grid coded by region

17D O2/Ar Samples collected during 6 cruises

14C PP: why another method?

In vitro effects are a big unknown (Marra, 2002)

Uncertainty in what it actually measures (Marra, 2002) Something between GCP and NCP,

closest to net primary production (NPP) Recycling of labeled C Some labeled C is dissolved

(depending on methodology either included/excluded)

Snapshot estimate (6 to 24 hours) Logistical constraints

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17Δ in situ GOP Method Uses a mixed layer O2 and O2-isotope

budget to estimate GOP in the mixed layer Luz and Barkan (2000)

GOP = Kgas* [O2]sat * 17D not sensitive to respiration More terms in the coastal ocean (i.e.

coastal upwelling, curl-driven upwelling, horizontal transports)

Must convert from O2 to C Not based on an incubation

(17Δdiss – 16)

(249 – 17Δdiss)

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Ocean Range of 17Δ Values

Purely Photosynthetic O2 249±15 per meg

Purely Gas Exchange O216±2 per meg

Half Photo + Half Gas Exchange O2 132 per meg

Measuring 17Δ yields a direct estimate of the proportion of O2 from air and photosynthesis.

15Locations of 17D measurements to date, from Juranek and Quay (2013)

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O2/Ar in situ NCP method NCP estimates (in O2 terms) are based on

mixed layer budgets for [O2] and [Ar] NCP = Kgas * [O2]sat * ( – 1) NCP/GOP a measure of export efficiency

from one measurement Does NOT depend on gas exchange (Kgas)

NCP/GOP is comparable to f-ratio 2x N/G ~ f-ratio (new production/net primary

production)

(O2/Ar)meas

(O2/Ar)sat

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Spatial maps of 17Ddiss and biological O2 saturation (from O2/Ar)

• Samples collected at up to 50 of 66 standard CalCOFI stations compared to 16 productivity (14C-PP) stations

August August

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Variability of 17D-GOP and O2:Ar-NCP

Annual NCP and GOP in mmol O2 m-2 d-1

0

50

100

150

200

250

300

350

N. Inshore S. Inshore Cal. Curr. Offshore CC grid

NCPGOP

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17D-GOP : 14C-PP

From Juranek and Quay (2013)

MBARI (Munro and Quay, unpublished data)

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Comparison of NCP/GOPStudy Location Authors

NCP/GOPO2 terms

NCP/NPPC terms

NCP/NPPLaws et al (2000)

CalCOFI – Entire GridCalCOFI – N. InshoreCalCOFI – Offshore

Munro et al. 2012

0.16±.060.20±.06 0.15±.06

0.31±.120.39±.12 0.29±.12

0.260.380.18

HOTBATSSubarctic N. PacificEquatorial Pacific

Southern Ocean

North Atlantic – bloom – annual

Quay et al. 2010Barkan et al. 2009Juranek et al. 2012Hendricks et al. 2005Stanley et al. 2010Reuer et al. 2007Hamme et al. 2010Quay et al. 2012

0.19±.080.13±.050.08 - 0.130.06±.05

0.08 - 0.13

0.35±.130.07±.06

0.38±.150.25±.100.15 - 0.250.12±.10

0.15 - 0.25

0.68±.25 0.14±.12

0.150.140.350.12

0.70

0.500.50 Coastal Ocean NCP/GOP ratio similar to open ocean

(unexpected)

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Particle Export Ratio

As predicted by the Dunne et al. 2007 algorithm which is a function of chl a and SST From Sarmiento and Gruber

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POC Export Production

From Sarmiento and Gruber

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Conclusions I 17D-GOP shows seasonality nearshore 17D-GOP consistently 5-7x 14C-PP and 4x

VGPM 17D-GOP/14C-PP = 2-3x at MBARI Suggests that CalCOFI 14C-PP

underestimates NPP due to methodological effects in 14C-PP

Cannot rule out variability in O2/C NCP:GOP ratios close to ratios observed

in the open ocean (0.1 to 0.2) Higher ratios than predicted by export

models offshore

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Variability in NCP at CalCOFI over the last

three decades

Trends in O2 in the S. Cal. Current

%change in O2 1984-2006

O2 trends at ~250 m depthFrom McClatchie et al. 2010

Bograd et al. 2008

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Methods: Estimating Biological O2 saturation

using O2 saturation Consistent

relationship between biological O2 saturation and O2 saturation

Estimated for each region/season

O2 and nitrate budgets constructed: upwelling terms; horizontal advection; time rate of change; NCP

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NCP anomaly calculated by differencing quarterly NCP with long-term mean for month of cruise

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Longterm NCP trends in the South CCS

MEI: Multivariate ENSO Index (Wolter and Timlin 1998)PDO: Pacific Decadal Oscillation (Mantua et al. 1997)NPGO: North Pacific Gyre Oscillation (Di Lorenzo et al. 2008)

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Conclusions II Negative NCP anomalies in response to strong El

Niño events (e.g., 1987, 1991-92, 1998) Less signficant NCP response to weak El Niño and La

Niña events. Since 2007, positive NCP anomalies based on all NCP

estimates (i.e., O2:Ar, nitrate budget, 15N incubations and satellite NPP)

NCP trends over the past three decades suggest that export of organic material to depth within the CalCOFI grid not responsible for lower O2 concentrations at depth observed by Bograd et al. (2008) and McClatchie et al. (2010)

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Questions?