Ocean Productivity - Mediterranean Oceanic Data Base (MODB)

Report
Ocean Productivity:
A Personal Perspective
John Marra
Brooklyn College,
City University of New York
13-17 May 2013
45th Liege Colloquium
1
st
1
I missed the
Liege
Colloquium (1969)
What’s happened over the last 44 years?
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And now I live in Brooklyn…
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A Review
1980s
•
•
•
•
1990s
• Method issues? • Biogeochemistry
(JGOFS)
• Emergence of
• Ocean Color!
bio-optics
• Picoplankton
1970s • Microbial loop
• Iron hypothesis
Eppley’s Temp.
•
vs Growth
•
Nutrient kinetics
•
‘Patchiness’
Information
theory
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2000s
Global scales
-omics
Pumps:
biological and
microbial
4
Plankton Rate Processes in Oligotrophic
OceanS (PRPOOS)
Spring, 1983
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But through it all, there has
been one theme, one goal:
“…determination of time-varying plankton
productivity in the world ocean…”
-Barber and Hilting (2002) (emphasis mine)
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14Carbon
14CO
2
+ H2O ->
14CH O
2
+ O2
• Basis of virtually all satellite algorithms for productivity
• Incubation from dawn-dusk very close to Net Primary
Production
• Characteristics invite methodological abuse and carelessness
– Easy
– Extremely Sensitive
– Always gives a ‘positive’ answer
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What We Don’t Know:
Lingering Problems
•
•
•
•
The depth of the Euphotic Zone, or Productive
Layer
Respiration and its components
Production and dynamics of dissolved organic
matter (DOM)
How do we determine primary production in
dynamic water columns
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AUTOTROPHIC
BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED
ORGANIC MATTER
EUPHOTIC DEPTH
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The Productive Layer of the Ocean
Horizontal extent of is OK
Vertical extent is unknown
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The Compensation Depth
(where P=R) defines the Euphotic
Zone…
…but it is never measured.
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Compensation
Depth
and the
Critical Depth
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Y Models for Water Column Productivity
and the Compensation Depth
Y = aB/4.6
Falkowski, 1981
Platt, 1986
Requires an accurate definition of the euphotic zone
(or productive layer)!
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Phytoplankton Respiration
from 14C Assimilation
• If 14C uptake measures net primary production (dawn
to dusk);
• If 14C is at intracellular isotopic equilibrium by the
end of the day; and
• If daytime R = nighttime R,
Then,
Phytoplankton R = f x the Dark Loss of C
(where f is a multiplier based on day:night hours, typically, 2 for 12:12)
Marra and Barber, 2004, GRL 31, L09314
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Summary of
14C-based
•
•
•
•
•
•
Rp Estimates
Grazing effects?
Diel changes in release of
DOC?
Observational error?
R in the light?
Day-night differences in R?
Mehler reaction?
Marra, 2009, AME
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The Compensation Depth (where P=R)
1%Eo
P=R is at a depth that
•Encompasses auto. Biomass,
•Equals 1% Ed(490)
(satellite connection?)
13-17 May 2013
ONDEQUE program,
NW Atlantic, 2008
Marra et al., submitted
P=R
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…but in the North Pacific…
Ed(z) = Ed(0)e(-Kdz)
The compensation depth is probably determined by biology, not light depth
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AUTOTROPHIC
BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED
ORGANIC MATTER
EUPHOTIC DEPTH
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CO2
Communication?
CO2
Source
Phytoplankton
Primary Production
Fate
inorganic compounds
extracellular release, grazing,
lysis, solubilization
DOM
Export to deeper waters & sediments through
aggregate and particulate sinking
•
•
•
•
Bacterial
Bacterial
Remineralization
remineralization
bioavailability
Lateral
transport
Advection
Estimated that 50% of primary production routed through dissolved fraction
DOM production cannot be captured by satellite sensors
Utilization of labile DOC will be as rapid as photosynthetic production
Not typically measured in productivity experiments
– O2 evolution/CO2 consumption will include it,
– 14C uptake may not
– Won’t be measured in particle production methods
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AUTOTROPHIC
BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED
ORGANIC MATTER
EUPHOTIC DEPTH
…in a dynamic water column
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The view of the
seasonal re-stratification
from a mooring at
60N/20W in the North
Atlantic (south of
Iceland)
Plueddemann et al., 1995, JGR
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Changes in thermal structure & phytoplankton from shipboard
Diatoms
.2-.3 mg Chl l-1
Phaeocystis
3-4 mg Chl l-1
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The kind of ‘container’
Physically very dynamic in situ volume
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Very non-dynamic volume
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Primary Production in the Ocean:
From the Synoptic to the Global Scale
AUTOTROPHIC
BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED
ORGANIC MATTER
EUPHOTIC DEPTH
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You can´t know
Love
Production
without the
Loss
Respiration
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Remembering Two Greats
1927-2012
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1933-2012
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Merci!
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Extras
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ONDEQUE, PP
and Rp for
stations in the
NW Atlantic
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Productivity has known limits
1. Growth rate as a
function of temperature
(Eppley,1972)
2. The maximum
rate of photosynthesis
normalized to
chlorophyll-a and
per hour, Pbmax,
will be ≤ 25
(Falkowski, 1981)
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3. The quantum yield. 8
quanta of light are required to
evolve 1 mol O2, thus, the
quantum yield will be < 0.1
(in practice)
(e.g., Bannister and
Weidemann, 1983)
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Global Ocean Productivity Through the ‘Ages’
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Biomass: Changes in POC
•
•
•
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Good for estimating
particle production
Doesn’t measure DOC
production
There are many more
optically-based
measurements of
production in
development
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Carbon
CO2 + H2O -> CH2O + O2
• It’s carbon! (no worries about value of the the
photosynthetic quotient), but…
• Precision is too low for most open ocean work
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Y modeling:
Northern Gulf of Mexico
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“…the results of the 14C method fall somewhere between the net
phytoplankton production and total photosynthesis, but exact
evaluation of the meaning of the experiments will require an
extensive experimental programme”
G. A. Riley (ca. 1954)
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Primary Productivity
“Let me count the ways…”
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Comparing Fluxes: In Situ and in
Containers
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Over 13 days (mixed layer):
• Production = 970
mmols C m-2
• Total increase in POC =
520 mmols C m-2
• Trap flux = 507 mmols
C m-2
• (234Th estimates are
about half the trap
flux.)
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m
The JGOFS North Atlantic Bloom
Experiment, Spring 1989
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Synthesis of Energy from Light
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Productivity Measurements
• Two choices:
– Fluxes from in situ dynamics
– Fluxes occurring in bottles
• Each has advantages and disadvantages
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