TABLE 1.
Rates of [15N]NO3− reduction to [15N]N2 and [15N]NH4+ from each of the six orange and six white laboratory-incubated FLSB mat pieces
| Mat | Sitea | Treatmentb | Protein content (μg · liter−1) | Production rate (pmol N · [μg protein]−1 · h−1)c |
|||||
|---|---|---|---|---|---|---|---|---|---|
| [15N]N2 |
[15N]NH4+ |
||||||||
| Whole mat | Epibionts | FLSB | Whole mat | Epibionts | FLSB | ||||
| White | UM | SW | 4.4 | 652 ± 94 | 0 ± 0 | 652 ± 94 | 168 ± 9 | 0 ± 0 | 168 ± 9 |
| SW | 2 | 1,140 ± 234 | 106 ± 145 | 1,034 ± 275 | 183 ± 19 | 0 ± 0 | 183 ± 19 | ||
| +HS− | 1.2 | 1,016 ± 157 | 0 ± 0 | 1,016 ± 157 | 611 ± 40 | 347 ± 109 | 264 ± 116 | ||
| CH | SW | 8.2 | 583 ± 39 | 40 ± 29 | 543 ± 49 | 251 ± 22 | 47 ± 10 | 204 ± 24 | |
| +HS− | 23 | 174 ± 4 | 45 ± 8 | 129 ± 9 | 103 ± 9 | 14 ± 1 | 90 ± 9 | ||
| +DOC | 13.9 | 847 ± 55 | 195 ± 31 | 651 ± 63 | 346 ± 32 | 25 ± 10 | 321 ± 33 | ||
| Orange | UM | SW | 19 | 110 ± 15 | 115 ± 59 | 0 ± 61 | 6 ± 23 | 21 ± 10 | 0 ± 25 |
| SW | 15 | 86 ± 12 | 91 ± 35 | 0 ± 37 | 87 ± 12 | 1 ± 0 | 86 ± 12 | ||
| +HS− | 9.7 | 133 ± 15 | 263 ± 101 | 0 ± 102 | 419 ± 37 | 24 ± 8 | 395 ± 38 | ||
| CH | SW | 2.5 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 949 ± 61 | 17 ± 0 | 932 ± 61 | |
| +HS− | 6.9 | 0 ± 0 | 0 ± 0 | 0 ± 0 | 134 ± 18 | 18 ± 3 | 116 ± 18 | ||
| +DOC | 4.4 | 45 ± 12 | 0 ± 0 | 45 ± 12 | 54 ± 4 | 7 ± 4 | 47 ± 6 | ||
Sampling locations were Ultra Mound (UM) and Cathedral Hill (CH); more details can be found in Table S1 and Fig. S1.
Treatments were seawater only (SW), seawater + HS− (+HS−), and seawater + dissolved organic carbon (+DOC) in the form of acetate.
Rates were calculated as the slope of the linear regression of the time points displayed in Fig. 1. Uncertainty in these rates was calculated as the standard error of the slope. The “whole mat” rate is the rate calculated from the first phase of each incubation, when FLSB filaments were intact. The “epibionts” rate is the rate calculated from the second phase of each incubation, after the FLSB filaments were destroyed. The “FLSB” rate is the whole mat rate minus the epibionts rate. This rate represents the activity of only the FLSB filaments. In many cases, the whole mat and FLSB rates are similar, because there was very little activity following filament destruction, demonstrating that the filaments were responsible for most of the total mat activity.