Lecture 15 Respiration

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Lecture 15 Respiration
New Production O2 Mass Balance Stokes
Law Sediment Traps 234Th Method Aerobic
Respiration Apparent Oxygen Utilization
(AOU) Regenerated and Preformed Nutrients Revised
RKR Ratios
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Global Carbon Fluxes
Export Flux
f 11/50 22
Sarmiento and Gruber
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Food Web Cartoon
Follow the N! Follow the C! Follow the O2!
Fe plays a role!
DON
Euphotic Zone (100m)
At steady state New NO3 O2 flux to atm
PON (and DON) export
PON
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Total Global New Production from NO3 upwelling
(from Chavez and Toggweiler)
estimated upward velocity, NO3 concentration
advected up and then
new production
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O2 Flux Method
Gas exchange
Write a mass balance
P ? O2
R
Mixing
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O2 Flux Method
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Marine Particles- basic facts Methods
classically define suspended vs. sinking
particles ? filtration ? sediment
traps Methods matter!
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Marine Particles- basic facts
Settling velocity proportional to (radius)2
density difference ? size matters ? and so
does density (ballast sinking speed) ? and so
does chemistry (degradation surface properties)
Sources biogenic material dominates surface
open ocean vs. inorganic/detrital
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What are the characteristics of the particles
that sink?
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The Fabulous Faecal Photo from Debbie Steinberg
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Mesozooplankton A copepod
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Marine snow aggregates
Inanimate particles greater than 0.5 mm
diameter The principal vehicles for downward
particle flux
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Diatoms rule! (the upper ocean POC flux) ?
large ? rapidly sinking ? bSi ballast ?
bioprotection ? mass aggregation
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• Settling Rate - You can calculate the flux!
• Estimated from Stokes Law of Settling.
• This equation was derived assuming smooth,
  spherical particles
• sinking rate Us a B r2 (cm sec-1)
• where
• r is a linear dimension, the equivalent spherical
  radius of the particle
• is a shape factor
• The density difference, or excess density, is
  written as Dr.
• B is a parameter that depends on the nature of
  the fluid and the particulate material
• but not on size.
• B 2 g (rp - rw) / 9? (cm-1 sec-1)
• rp is the density of particles and rw is the
  density of seawater
• For water (at 20?C) the density of seawater is rw
  1.025 g cm-3
• and viscosity ? 0.01 g cm-1 sec-1. The value
  of g is 980 cm sec-1.

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DDensity (rp rw) versus particle size for marine
snow particles
Is ballast required? Calc Us for 1mm and ??10-3
Aldredge and Gotschalk, 1988
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Sediment trap techniques
Large Diameter cylinder/cone type sediment traps
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Particle Interceptor Traps (PITs) Knauer and
Martin (Moss Landing)
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Marine Particles- Tough to Catch
Horizontal flow
Sinking particles do not sink vertically ?
sinking velocity 10s - gt500 m/day ?
horizontal velocity few - 10s cm/sec (avg.
sinking particle- 2 m drop 270m trajectory
during 30 min talk)
Problems w/traps swimmers surfers gliders solubili
zation turbulence
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Martin et al (1987) VERTEX - Classic Sediment
Trap Data
Martin Curve FPOC FPOC(100m) (Z/100m)-b where Z
depth b 0.86 F100m 1.53 molCm-2y-1
Open Ocean Composite
mol C m-2 y-1
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Primary Production by Ocean Provinces from POC
Export (from Martin
et al., 1987)
Compare with 7.2 Gty-1 in earlier table for
upwelled NO3 new production!
f 7.4 / 51 14
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Scavenging Tracers in U-Th Series
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The isotopes of Th, Pa, Pb and Po react rapidly
with particles and are useful as particle
tracers 234Th (24.1d) 230Th (7.5 x 104
y) 210Pb (22.3y) 210Po (138d) 231Pa (3.2 x
104 y)
Secular equilibrium provides reference t1/2
parent gtgt t1/2 daughter ?ND / ?t lP NP -
lD ND at steady state 0 AP
- AD or AP AD
see EH p. 193
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For particle reactive tracers, There is an
additional loss term for dissolved species
P parent D daughter N concentration
0
?ND / ?t lP NP - lD ND - ls ND
First Order Scavenging Term
at steady state
lP NP lD ND ls ND
AD lD ND ND AD / lD
AP AD ls / lD AD
AP lD AD lD ls AD
Scavenging removal rate constant lS (AP AD)
/ AD x lD
Scavenging Residence Time tS 1 / ls
see Emerson and Hedges Eqn VI-27 and VI-28
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Thorium-234 approach for estimating particle
export
234Th



depth (m)


238U

At Steady State (A238U - A234Th) ?234Th Z
234Th Export (dpm m-2 d-1) Measure C/234Th on
sinking particles --gt Carbon Export
see Emerson and Hedges Eqn VI-31 Eqn VI-32
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Particle and 234Th Export
Coale Bruland 1987
Vertical zonation of 234Th removal
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EqPac 234Th Data - 1992
12ºN to 12ºS at 140ºW
mild El Nino
cold tongue
Murray et al 1996
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234Thdef meridional Section from EqPac
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Org Carbon/234Th ratio from sediment traps
from base of euphotic zone
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Export Flux
Survey II gt Survey I (El Nino) (Cold Tongue)
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Comparison of new and export production
Not too bad!
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Aerobic respiration Oxygen is consumed and
nutrients are released. (CH2O)106(NH3)16(H3PO4)
138 O2 Algal Protoplasm
? bacteria 106 CO2 16 HNO3
H3PO4 122 H2O trace elements The
oxidation of the NH3 in organic matter to NO3
is referred to as nitrification
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Apparent Oxygen Utilization (AOU) Apparent
Oxygen Utilization or AOU. AOU is defined
as AOU O2' - O2 where O2' value of O2
the water would have if it was in equilibrium
with the atmosphere at the temperature and
salinity of the water. This is called
saturation. This implies that all waters are in
equilibrium with the atmosphere (100 saturated)
when they sink to become the deep ocean water.
O2 is the dissolved oxygen actually measured in
the same water sample.
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Nutrients versus AOU
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Oxidative and Preformed Nutrients versus Depth
1 mol O2 106/138 mol CO2 16/138 mol
HNO3 1/138 mol H3PO4 consumed 0.77 CO2
0.12 HNO3 0.0072
H3PO4
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DP PO4 - PO4? RPO4/O2 x AOU DN NO3
- NO3? RNO3/O2 x AOU
on s? 27.0 to 27.2
Takahashi et al, 1985
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Remineralization Ratios versus Depth
average for 400m to 4000m P N C
O2 1 161 11714 17010
Anderson and Sarmiento, 1994)
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It is clear that more O2 (170 moles) is
actually required to respire sinking organic
matter than was originally calculated from the
RKR equation (138 moles). The RKR type organic
matter has an oxidation state as for carbohydrate
(CH2O). Real plankton have 65 protein, 19
lipid and 16 carbohydrate (from NMR
studies) The higher O2 demand suggests that
sinking organic matter has more of a lipid-like
nature. Instead of CH2O O2 CO2
H2O More like CH2 3/2 O2 CO2 H2O
Real plankton biomass is more like
C106H177O37N17S0.4 instead of
C106H260O106N16 Complete oxidation requires 154
moles of O2 instead of 138
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