Dataset: Zooplankton Biomass
Deployment: AT21-04

Sampling and Analytical Methodology:

Biomass was determined using a 1-m2, 202-micron mesh MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) (net_id = 3) towed through the upper 150 m or occasionally the upper 500 m of the water column. The following discrete depth intervals were sampled on the upcast for 150m tows: 0-25 (or 0-10 and 10-25), 25-50, 50-75, 75-100 (or 50-100), and 100-150 m. The following discrete depth intervals were sampled on the upcast for 500m tows: 0-25 (or 0-10 and 10-25), 25-50, 50-75, 75-100 (or 50-100), 100-150, 150-200, 200-300, 300-400, and 400-500 m. Occasionally at shallow depth stations, a double oblique tow using a rectangular frame (0.8 x 1.2 m) single net with 202-micron mesh (net_id = 1) or a circular frame (1-m diameter) single net with 202-micron mesh (net_id = 2) was performed in surface waters. Both day and night tows were performed, and occasionally paired day/night tows at the same station. Each sample was split, with one-half of each sample used for the determination of biomass. Each sample was size-fractionated by wet sieving through nested sieves of 0.20 mm, 0.5 mm, 1 mm, 2 mm, and 5 mm mesh. Zooplankton in each size class were transferred onto pre-weighed disks of 0.2-mm nitex mesh, rinsed with deionized water, and frozen at sea (-20˚C or -80˚C). At our home laboratory samples were thawed and weighed (=wet weight), and then dried for at least 24 h at 60 oC and weighed (=dry weight).

Net Types:
Description of net_id values.  All nets used a 202-micron mesh.

1 = rectangular frame (0.8 x 1.2 m) single net
2 = circular frame (1-m diameter) single net
3 = MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) 1-m2