12.755 L06 Part IPreviously: Metal speciation theory and biological cellular uptake theory

Today: Connecting speciation and cellular uptake in the marine water column,

and several generations of iron modeling

Return to theme of introduction lecture:

What are the processes controlling the distribution of hybrid type metals?

How should they be parameterized in models?

Do we have enough data yet?

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Iron as a limiting nutrient in HNLC regions (Review of Iron Fertilization Experiments Boyd et al., 2007, Science)

Purposeful (white crosses) and natural (red crosses) Fe enrichment studies have shown Fe limitation of phytoplankton growth.

Studies integrating iron modeling

• 1D – vertical profiles, no horizontal processes (Johnson 1997; Weber et al., 2007)

• 2D – GEOTRACES sections, horizontal processes

• 3D – GCM with iron (Fung, 2000; Archer and Johnson, Moore et al, 2002, 2004; Oschilles, Moore and Braucher 2008)

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4

5

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Fe:C determined using AOU: 2-13 mol Fe mol-1 C, constant value of 5 not correct7

Available iron database in 1999

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10

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Based on the Martin Carbon Power Law:Modified for production of dissolved iron, where Q is cellular quota (Fe:C ratio),

with first order Fe scavenging with a “ligand protection term” (Fesoly)

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“Ligand Protection” from scavenging is standard in models now

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0 0.5 1 1.5-4000

-3000

-2000

-1000

0Dissolved Iron

-0.4 -0.2 0 0.2 0.4-4000

-3000

-2000

-1000

0Diffusion term

0 0.1 0.2 0.3 0.4-4000

-3000

-2000

-1000

0Production term

-6 -4 -2 0

x 10-3

-4000

-3000

-2000

-1000

0Scavenging term

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0 0.05 0.1 0.15 0.2-4000

-3000

-2000

-1000

0Dissolved Co

nM

Dep

th (

m)

-0.03 -0.02 -0.01 0 0.01-4000

-3000

-2000

-1000

0Diffusion term

nM

Dep

th (

m)

0 0.01 0.02 0.03-4000

-3000

-2000

-1000

0Production term

nM

Dep

th (

m)

-8 -6 -4 -2 0

x 10-4

-4000

-3000

-2000

-1000

0Scavenging term

nM

Dep

th (

m)

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1D vs 2D

Noble and Saito, preliminary data

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Vertical fluxes require a source of metal Another clue in relative importance of vertical versus horizontal processes is

M:P ratios

• If 1D processes dominate, Hybrid Metal:P correlations can be supported (metal and P are both subject to remineralization advection etc)

• If 2D processes dominate, unclear how Hybrid Metal:P are maintained. Point sources of metal likely do not have stoichiometric additions of P as well.

Cobalt - Phosphate Relationship in the Central North Pacific

Total Dissolved Cobalt (pM)

0 20 40 60 80 100 120 140

Pho

spha

te ( M

)

0.0

0.5

1.0

1.5

2.0

2.5

Stn 1Stn 2Stn 3Stn 4Stn 5Stn 6Stn 8

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Atm

osph

eric

and

ot

her

abio

tic in

puts

Remine

raliz

ation

Biolog

ical U

ptak

e

Phosphate

Hyb

rid-t

ype

met

al

Biotic and abioticS

cavenging

Uptake by biota

entrainment

Phosphate

Cob

alt

Higher QCo

Co:P~248

Lower QCo

Co:P~36

Upwelling

b.

a.

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Generations of iron modeling

Fung et al,. 2000 19

From Parekh, Fellows, Boyle Box-model study, sensitivity testing of ligand parameters

• Parekh, Boyle, Fellows GBC20

From Moore and Braucher 2008 BG

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From Moore and Braucher 2008 BG

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Colloidal = “dissolved” – solubleFeL is in all fractionsWu Boyle and Sunda, 2001 25

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Further reading: Iron modeling studies

• Johnson 1997• Inez Y. Fung,1 Stephanie K. Meyn,2 Ina Tegen,3 Scott C. Doney,4 Jasmin G. John,1 and James K. B. Bishop5

GBC 1999• Archer and Johnson GBC 2000• Moore et al.., 2002, 2004• Parakh, Fellows, Boyle, GBC 2004• Weber, Volker Oschilies Burchard, BG 2007• Moore and Braucher Biogeosciences, 2008 Sedimentary and mineral dust sources of iron to the world oceans.

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Societal Implications and Applications?

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