Table 3.
Pseudo-nitzschia standing stocks, daily fluxes of intact cells, and DA flux at VERTIGO K2 to mesopelagic depths
| VERTIGO NBST traps |
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| Measurement | ALOHA D1 | ALOHA D2 | K2 D1 | K2 D2 |
| Euphotic zone depth | 125 m | 125 m | 60 m | 60 m |
| Euphotic zone standing stocks (cells·m−2) | 1.1 × 106 | 2.2 × 107 | 4.2 × 108 | 8.6 × 107 |
| Trap depth, daily cell flux, cells·m−2·d−1 | ||||
| 150 m | 0–3.8 | 9.6 × 103 | 4.0 × 106 | 2.1 × 105 |
| 300 m | b.d.l. | b.d.l. | 1.6 × 106 | 2.3 × 106 |
| 500 m | b.d.l. | b.d.l. | 1.8 × 106 | 1.2 × 106 |
| Cell flux at 150 m as % of Pseudo-nitzschia standing stock | 0.02 | 0.04 | 1 | 0.24 |
| Trap depth, daily DA flux, μg·m−2·d−1 | ||||
| 150 m | m.d. | m.d. | 2.2 | 0.4 |
| 300 m | m.d. | m.d. | 0.9 | 4.4 |
| 500 m | m.d. | m.d. | 1.0 | 2.3 |
Pseudo-nitzschia cell fluxes were obtained from counts made on material collected from neutrally buoyant sediment traps (NBST) deployed for 3–5 d at 150, 300, and 500 m on the VERTIGO cruises. DA fluxes were calculated based on DA cell quotas that were obtained from DA measurements on corresponding phytoplankton net tow samples taken during the deployments. Euphotic zone depths (1% light level) were 125 m for ALOHA and 60 m for K2. Standing stocks of Pseudo-nitzschia were derived from counts on water samples taken near the surface (25 m at ALOHA, 25 m at K2) and near the base of the euphotic zones (125 m at ALOHA, 40 m at K2). The designation b.d.l. indicates “below detection limit”. Missing data are indicated by “m.d.” (Materials and Methods and SI Methods).