TABLE 3.
Rates of major processes occurring in sediments below the cyanobacterial mat for six ponds of the McMurdo Ice Shelf
| Pond | Incubation typea | Mean rate (nmol · cm−3 day−1) ± SD ofb:
|
|
|---|---|---|---|
| Methanogenesis | Sulfate reduction | ||
| Orange | ST | 100.9 ± 18.9 | 351.2 ± 63.7 |
| S1 | 14.2 ± 1.9 | 14.6 ± 1.3 | |
| S2 | 2.4 ± 0.5 | 0.02 ± 0.01 | |
| A | 3.6 ± 0.8 | 6.8 ± 0.4 | |
| Skua | ST | 156.6 ± 32.5 | 314.2 ± 39.6 |
| S1 | 31.6 ± 1.9 | 21.8 ± 1.0 | |
| S2 | 7.7 ± 4.1 | 0.14 ± 0.03 | |
| A | 21.8 ± 0.6 | 15.9 ± 6.7 | |
| P-70 | ST | 108.1 ± 6.2 | 143.3 ± 33.6 |
| S1 | 70.3 ± 18.0 | 22.1 ± 7.1 | |
| S2 | 12.5 ± 7.6 | 0.22 ± 0.01 | |
| A | 8.9 ± 0.5 | 11.2 ± 2.6 | |
| Fresh | ST | 99.9 ± 13.2 | 11.6 ± 1.2 |
| S1 | 1.25 ± 0.3 | 0.3 ± 0.02 | |
| S2 | 0.06 ± 0.02 | 0.006 ± 0.002 | |
| A | 0.02 ± 0.01 | <0.01 | |
| Brack | ST | 3.38 ± 0.06 | 124.1 ± 20.9 |
| S1 | 0.15 ± 0.03 | 42.9 ± 2.9 | |
| S2 | 0.09 ± 0.01 | 0.18 ± 0.018 | |
| A | 0.06 ± 0.01 | 27.7 ± 9.2 | |
| Salt | ST | 1.11 ± 0.03 | 160.8 ± 1.2 |
| S1 | 0.27 ± 0.10 | 9.3 ± 4.6 | |
| S2 | <0.001 | 0.23 ± 0.17 | |
| A | 0.04 ± 0.01 | 12.1 ± 2.3 | |
a
Abbreviations: ST, short-term incubation at 4°C for up to 10 days; S1, seasonal summer incubation (4°C) up to 4 months; S2, seasonal winter incubation (−18°C) up to 8 months; A, 1-year in situ incubation.
b
Values for ST were determined on sediments collected in the field in January 1997 in the linear range for [35S]sulfide and methane production. Values for S1 and S2 were determined for sediments collected in January 1998. Values for A were determined from in situ incubations from January 1997 to January 1998. Values are means of at least triplicate determinations ± 1 SD.