ocean productivity: a personal perspective

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)

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What’s happened over the last 44 years?


And now I live in Brooklyn…

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A Review

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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


Plankton Rate Processes in Oligotrophic OceanS (PRPOOS)

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Spring, 1983


But through it all, there has been one theme, one

goal:

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“…determination of time-varying plankton productivity in the world

ocean…”

-Barber and Hilting (2002) (emphasis mine)


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


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


AUTOTROPHIC BACTERIAL, HETEROTROPHIC

RESPIRATION

DISSOLVED ORGANIC MATTER

EUPHOTIC DEPTH


The Productive Layer of the Ocean Horizontal extent of is OK

Vertical extent is unknown


The Compensation Depth (where P=R) defines the

Euphotic Zone…

…but it is never measured.


Compensation Depthand the Critical Depth


Y Models for Water Column Productivity

and the Compensation Depth

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Falkowski, 1981

Y = aB/4.6

Requires an accurate definition of the euphotic zone (or productive layer)!

Platt, 1986


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


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


The Compensation Depth (where P=R)

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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?)


…but in the North Pacific…

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Ed(z) = Ed(0)e(-Kdz)

The compensation depth is probably determined by biology, not light depth



RESPIRATION


EUPHOTIC DEPTH


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?



RESPIRATION


EUPHOTIC DEPTH

…in a dynamic water column


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)


Changes in thermal structure & phytoplankton from shipboard

Phaeocystis3-4 mg Chl l-1

Diatoms.2-.3 mg Chl l-1


The kind of ‘container’Physically very dynamic in situ volume Very non-dynamic volume



RESPIRATION


EUPHOTIC DEPTH

Primary Production in the Ocean: From the Synoptic to the Global Scale


You can´t know

without theProductionLove

RespirationLoss

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Remembering Two Greats

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1933-20121927-2012


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 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)


Global Ocean Productivity Through the ‘Ages’


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


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


Y modeling: Northern Gulf of Mexico


“…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)


Primary Productivity“Let me count the ways…”

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Comparing Fluxes: In Situ and in Containers


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


Synthesis of Energy from Light


Productivity Measurements

• Two choices: – Fluxes from in situ dynamics– Fluxes occurring in bottles

• Each has advantages and disadvantages

ocean productivity: a personal perspective

Documents

liege colloquium41970seppleys

liege colloquiumsummary

liege colloquium10

liege colloquium714carbonbasis

liege colloquium3

liege colloquium8

liege colloquium17 edz

liege colloquium13 falkowski