Dataset: Zooplankton Abundance
Deployment: AT21-04

Sampling and Analytical Methodology:
Zooplankton abundance was determined using a 1-m2, 202-micron mesh MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) 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 was performed in surface waters (within top 25 m). Both day and night tows were performed, and occasionally paired day/night tows at the same station. Usually one-quarter of the tow was preserved in 4% buffered formaldehyde and used for determination of major taxa

At our home laboratory, zooplankton were identified using an Olympus SZX-10 dissecting microscope at 3-60x magnification under dark and bright field illumination, and grouped into major taxa using the following categories:
- ostracod
- siphonophore
- chaetognath
- copepod_calanoid
- copepod_harpacticoid
- copepod_cyclopoid
- decapod
- euphausiid
- doliolid
- medusae
- polychaete
- pteropod
- fish larvae
- amphipod
- stomatopod
- leptocephalus
- salp
- lucifer faxoni
- barnacle cyprid
- larvacean
- foraminfera
- lancelet
- cephalopod

The >2mm size fraction was counted in its entirety, the <2mm fraction was subsampled until a minimum of 200 individual animals were identified.