TABLE 7.
Calculation of carbon flow via acetate or H2O, CO2 to sulfate reduction and methanogenesis in pond sediments of the McMurdo Ice Shelf incubated at 4°C
| Pond | % Carbon flowa via:
|
|||
|---|---|---|---|---|
| H2 or CO2 to CH4 | Acetate to CH4 | Acetate coupled to sulfate reduction | H2 or CO2 coupled to sulfate reduction | |
| Orange (no freeze-thaw) | 24 | 0.3 | 50 | ND |
| Orange (freeze-thaw) | NDb | 0.3 | 55 | ND |
| Brack | <1 | 0.67 | 67 | >30 |
| Salt | <1 | 0.70 | 69 | >25c |
a
Values were determined using the data in Tables 5 and 6. They were calculated as percent contribution of acetate or H2 to process (sulfate reduction or methanogenesis) × (rate of process)/(rate of methanogenesis + rate of sulfate reduction). For Orange Pond the previous determination of 100% H2 utilization being accounted for by methane (11) was used in the calculation, and for Brack Pond the value of 100% H2 utilization accounting for sulfate reduction (see Table 6 and Fig. 4) was used.
b
ND, not determined.
c
Based on the results for Brack Pond showing 100% H2 utilization by sulfate reduction.