Table S1. Organic carbon fluxes in the ocean (Pg C y-1)
Near-shore
Shelf Slope Open Total
Area (1013 m2)1
0.71
0.95
2.24
31.07 34.97
Net Primary Production Phototrophs1
Organic Carbon Export1
Euphotic Zone Respiration1
Dark Ocean Respiration1
Sediment Respiration1
Organic Carbon Burial1
3.61
1.14
2.47
0.04
0.53
0.48
2.87
0.86
2.01
0.34
0.29
0.19
4.06
1.00
3.06
0.64
0.22
0.1
43.1
6.55
36.0
6.24
0.19
0.01
Euphotic Zone Chemoautotrophy2
Dark Ocean Chemoautotrophy3
Sediment Chemoautotrophy4
0.016 0.013 0.020 0.237 0.286
0.002 0.006 0.010 0.096 0.114
0.175 0.116 0.077 0.004 0.372
53.6
9.55
44.0
7.26
1.23
0.78
1: Oceanic depth regimes, their surface area (m2) and estimates for net primary
production, organic carbon export, respiration in the euphotic zone, the dark
ocean and sediment, and organic carbon burial are from Dunne et al. [2007]
2: Euphotic zone chemoautotrophy is calculated by dividing the euphotic zone
respiration with the Redfield C:N ratio (6.6) and assuming one mole of carbon
dioxide is fixed per 10 mole of ammonium oxidized [Tijhuis et al., 1983; Wuchter
et al., 2006]. Only a fraction of the ammonium regenerated in the euphotic zone
is available for nitrification (0.43), the remaining is consumed by phytoplankton.
This fraction is calculated from data by Yool et al. [2007] for their median
specific nitrification rate of 0.2 (d-1). The mean of their dataset was 0.55 d-1. If
the lower specific nitrification rate of their sensitivity studies is used (0.02 d-1),
only 16% of the ammonium regenerated is nitrified and euphotic zone carbon
fixation by nitrifiers will then total 0.11 Pg C y-1.
As an example the open-ocean calculation: 36.5 Pg C is first converted to 3.04
Pmol C. This relates to 3.04/6.6 (=0.46 Pmol N) ammonium regeneration, which
in turn yields 0.46/10*0.43 (=19.8 Tmol C) inorganic carbon fixation and thus
19.8*12= 237 Tg C y-1.
3: Dark ocean carbon fixation is calculated similarly as for the euphotic zone but
all ammonium regenerated is made available for nitrifiers.
4: Chemoautotrophy in sediment is mainly supported by re-oxidation of reduced
compounds generated during anaerobic processes, with a small contribution by
sediment nitrification (0.9 to 1.4 % of sediment respiration, [Middelburg et al.,
2007]). Re-oxidation efficiencies vary from 80% in coastal and shelf sediments to
19% in deep-sea sediments. Sediment respiration estimates of Dunne et al.
[2007] are combined with global water-depth resolved nitrification and
anaerobic respiration numbers of Middelburg et al. [1996] and an ammonium
used to carbon fixed ratio of 10 and a sulfide oxidized to carbon fixed ratio of 2 to
arrive at overall efficiencies between 31 and 41% in coastal and ocean margin
sediments and 1.5 to 1.7 % in deep-sea sediments. For instance, near-shore
sediment support a chemolithoautotrophy of 0.175 Pg C y-1 based on a global
respiration rate of 0.53 Pg C y-1 and an overall efficiency of 33%. Assuming a
sulfide oxidized to carbon fixed ratio of 5 would lower the overall efficiencies in
coastal and ocean margins sediments to 10-16% and sediment
chemolithoautotrophy would then total 0.15 Pg C y-1.