Lecture Note - Atmospheric and Oceanic Sciences

Report
Biological Production Rates in the
Southern California Current System
David Munro
University of Washington
1
Acknowledgements


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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)
2
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
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Primary Production and Carbon
Export in the Coastal Ocean
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Global aquatic PP from satellites ~45-50 Pg C y-1 (Carr
et al., 2006)
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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 (502000 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
Sea surface chlorophyll
From Sarmiento and Gruber
5
Net Primary Production
From Sarmiento and Gruber
6
Air-Sea C Flux in the Coastal Ocean
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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
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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)
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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
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Gross oxygen production (GOP)
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Net community production (NCP)
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using 17Δ of dissolved O2
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
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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
 CalCOFI grid coded by region

17D
O2/Ar Samples collected
during 6 cruises
Annual Mean Surface
Chl a in mg m-3 from
Photobiology Group
(SIO)
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14C

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In vitro effects are a big unknown (Marra, 2002)
Uncertainty in what it actually measures (Marra,
2002)
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PP: why another method?
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
17Δ
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Uses a mixed layer O2 and O2-isotope budget to
estimate GOP in the mixed layer
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in situ GOP Method
Luz and Barkan (2000)
(17Δdiss – 16)
(249 – 17Δdiss)
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
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Ocean Range of 17Δ Values
Purely Photosynthetic O2
Half Photo + Half Gas Exchange O2
Purely Gas Exchange O2
249±15 per meg
132 per meg
16±2 per meg
Measuring 17Δ yields a direct estimate of the
proportion of O2 from air and photosynthesis.
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Locations of 17D measurements to date, from Juranek and Quay (2013)
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O2/Ar in situ NCP method
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NCP estimates (in O2 terms) are based on mixed layer
budgets for [O2] and [Ar]
NCP = Kgas * [O2]sat * ( (O2/Ar)meas
– 1)
(O2/Ar)sat
NCP/GOP a measure of export efficiency from one
measurement

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Does NOT depend on gas exchange (Kgas)
NCP/GOP is comparable to f-ratio
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2x N/G ~ f-ratio (new production/net primary production)
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Spatial maps of 17Ddiss and biological
O2 saturation (from O2/Ar)
August
August
• Samples collected at up to 50 of 66 standard CalCOFI
stations compared to 16 productivity (14C-PP) stations
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Variability of 17D-GOP and O2:Ar-NCP
350
300
250
200
NCP
GOP
150
100
50
0
N. Inshore S. Inshore Cal. Curr.
Offshore
CC grid
Annual NCP and GOP in mmol O2 m-2 d-1
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17D-GOP
: 14C-PP
MBARI (Munro and Quay,
unpublished data)
From Juranek and Quay (2013)
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Comparison of NCP/GOP
NCP/GOP
O2 terms
NCP/NPP NCP/NPP
C terms
Laws et al (2000)
Study Location
Authors
CalCOFI – Entire Grid
CalCOFI – N. Inshore
CalCOFI – Offshore
Munro et al. 2012
0.16±.06
0.20±.06
0.15±.06
0.31±.12
0.39±.12
0.29±.12
0.26
0.38
0.18
HOT
BATS
Subarctic N. Pacific
Equatorial Pacific
Quay et al. 2010
Barkan et al. 2009
Juranek et al. 2012
Hendricks et al. 2005
Stanley et al. 2010
Reuer et al. 2007
Hamme et al. 2010
Quay et al. 2012
0.19±.08
0.13±.05
0.08 - 0.13
0.06±.05
0.38±.15
0.25±.10
0.15 - 0.25
0.12±.10
0.15
0.14
0.35
0.12
0.08 - 0.13
0.15 - 0.25
0.70
0.35±.13
0.07±.06
0.68±.25
0.14±.12
0.50
0.50
Southern Ocean
North Atlantic – bloom
– annual
 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
 17D-GOP

shows seasonality nearshore
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
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Trends in O2 in the S. Cal. Current
O2 trends at ~250 m depth
From McClatchie et al. 2010
Bograd et al. 2008
%change in O2 1984-2006
Methods: Estimating Biological
O2 saturation using O2 saturation
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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
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long-term mean for month of cruise
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
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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?
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