Ocean Productivity: A Personal Perspective
Post on 22-Mar-2016
38 Views
Preview:
DESCRIPTION
Transcript
45th Liege Colloquium 113-17 May 2013
Ocean Productivity: A Personal Perspective
John MarraBrooklyn College,
City University of New York
45th Liege Colloquium 2
I missed the 1st Liege Colloquium (1969)
13-17 May 2013
What’s happened over the last 44 years?
45th Liege Colloquium 3
And now I live in Brooklyn…
13-17 May 2013
45th Liege Colloquium 4
A Review
13-17 May 2013
1970s• Eppley’s
Temp. vs Growth
• Nutrient kinetics
• ‘Patchiness’• Information
theory
1980s• Method
issues?• Emergence of
bio-optics• Microbial loop
1990s• Biogeochemist
ry (JGOFS)• Ocean Color!• Picoplankton• Iron
hypothesis2000s
• Global scales• -omics• Pumps:
biological and microbial
45th Liege Colloquium 5
Plankton Rate Processes in Oligotrophic OceanS (PRPOOS)
13-17 May 2013
Spring, 1983
45th Liege Colloquium 6
But through it all, there has been one theme, one
goal:
13-17 May 2013
“…determination of time-varying plankton productivity in the world
ocean…”
-Barber and Hilting (2002) (emphasis mine)
45th Liege Colloquium 713-17 May 2013
14Carbon
• 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
14CO2 + H2O -> 14CH2O + O2
45th Liege Colloquium 813-17 May 2013
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
45th Liege Colloquium 913-17 May 2013
AUTOTROPHIC BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED ORGANIC MATTER
EUPHOTIC DEPTH
45th Liege Colloquium 1013-17 May 2013
The Productive Layer of the Ocean Horizontal extent of is OK
Vertical extent is unknown
45th Liege Colloquium 1113-17 May 2013
The Compensation Depth (where P=R) defines the
Euphotic Zone…
…but it is never measured.
45th Liege Colloquium 1213-17 May 2013
Compensation Depthand the Critical Depth
45th Liege Colloquium 13
Y Models for Water Column Productivity
and the Compensation Depth
13-17 May 2013
Falkowski, 1981
Y = aB/4.6
Requires an accurate definition of the euphotic zone (or productive layer)!
Platt, 1986
45th Liege Colloquium 1413-17 May 2013
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
45th Liege Colloquium 1513-17 May 2013
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
45th Liege Colloquium 16
The Compensation Depth (where P=R)
13-17 May 2013
ONDEQUE program, NW Atlantic, 2008Marra et al., submitted
1%Eo
P=R
P=R is at a depth that• Encompasses auto. Biomass,• Equals 1% Ed(490)(satellite connection?)
45th Liege Colloquium 17
…but in the North Pacific…
13-17 May 2013
Ed(z) = Ed(0)e(-Kdz)
The compensation depth is probably determined by biology, not light depth
45th Liege Colloquium 1813-17 May 2013
AUTOTROPHIC BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED ORGANIC MATTER
EUPHOTIC DEPTH
45th Liege Colloquium 1913-17 May 2013
Phytoplankton Primary Production
DOM
CO2
Bacterial remineralization
extracellular release, grazing, lysis, solubilization
inorganic compounds
CO2
Bacterial Remineralization
Advection
Lateral transport
bioavailability
• 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
Export to deeper waters & sediments through aggregate and particulate sinking
Source FateCommunication?
45th Liege Colloquium 2013-17 May 2013
AUTOTROPHIC BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED ORGANIC MATTER
EUPHOTIC DEPTH
…in a dynamic water column
45th Liege Colloquium 2113-17 May 2013
Plueddemann et al., 1995, JGR
The view of the seasonal re-stratification from a mooring at 60N/20W in the North Atlantic (south of Iceland)
45th Liege Colloquium 2213-17 May 2013
Changes in thermal structure & phytoplankton from shipboard
Phaeocystis3-4 mg Chl l-1
Diatoms.2-.3 mg Chl l-1
45th Liege Colloquium 2313-17 May 2013
The kind of ‘container’Physically very dynamic in situ volume Very non-dynamic volume
45th Liege Colloquium 2413-17 May 2013
AUTOTROPHIC BACTERIAL, HETEROTROPHIC
RESPIRATION
DISSOLVED ORGANIC MATTER
EUPHOTIC DEPTH
Primary Production in the Ocean: From the Synoptic to the Global Scale
45th Liege Colloquium 25
You can´t know
without theProductionLove
RespirationLoss
13-17 May 2013
45th Liege Colloquium 26
Remembering Two Greats
13-17 May 2013
1933-20121927-2012
45th Liege Colloquium 27
Merci!
13-17 May 2013
45th Liege Colloquium 28
Extras
13-17 May 2013
45th Liege Colloquium 29
ONDEQUE, PP and Rp for
stations in the NW Atlantic
13-17 May 2013
45th Liege Colloquium 3013-17 May 2013
Productivity has known limits1. Growth rate as a function of temperature (Eppley,1972) 2. The
maximum rate of photo-synthesis normalized to chlorophyll-a and per hour, Pb
max, will be ≤ 25(Falkowski, 1981)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)
45th Liege Colloquium 3113-17 May 2013
45th Liege Colloquium 3213-17 May 2013
Global Ocean Productivity Through the ‘Ages’
45th Liege Colloquium 3313-17 May 2013
Biomass: Changes in POC• Good for estimating
particle production• Doesn’t measure
DOC production• There are many
more optically-based measurements of production in development
45th Liege Colloquium 3413-17 May 2013
CarbonCO2 + 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
45th Liege Colloquium 3513-17 May 2013
Y modeling: Northern Gulf of Mexico
45th Liege Colloquium 3613-17 May 2013
“…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)
45th Liege Colloquium 37
Primary Productivity“Let me count the ways…”
13-17 May 2013
45th Liege Colloquium 3813-17 May 2013
Comparing Fluxes: In Situ and in Containers
45th Liege Colloquium 3913-17 May 2013
The JGOFS North Atlantic Bloom Experiment, Spring 1989
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.)
m
45th Liege Colloquium 4013-17 May 2013
Synthesis of Energy from Light
45th Liege Colloquium 4113-17 May 2013
Productivity Measurements
• Two choices: – Fluxes from in situ dynamics– Fluxes occurring in bottles
• Each has advantages and disadvantages
top related