Methodology:

Data were gathered during an oceanographic cruise aboard the RRS James Clark Ross to the Atlantic Sector of the Southern Ocean (8th Dec 2016 to 6th Jan 2017). Depth discrete mesozooplankton samples to a maximum depth of 1000 m were collected by a MOCNESS net system (1m2 opening area, 330 µm meshes) along a transect across the Polar Frontal Zone between South Georgia and the Falkland Islands. The MOCNESS comprised 9 separate nets which opened in sequence such that the closing of one net opened the next; net 1 was open during the descent of the net to its maximum depth (1000 m) while the remaining 8 depths opened at regular intervals (about every 125 m) during the reascent to the surface (minimum depth 5m). Collected samples were immediately preserved in 4% buffered formaldehyde. Taxa were identified through examination by light microscopy by analysts at the Morski Institute, Poland. The abundance of each taxa within a sample was determined through examining a known fraction of the sample and then making an inverse multiplication of that fraction. Volumetric abundances (individuals m-3) were determined through dividing sample abundance by the volume of water sampled by the respective net. Net volume was mainly derived through a calibrated flow meter or, if that failed, through multiplying the net opening diameter by average speed of the vessel during hauling. This calculation assumes 100% net sampling efficiency and no avoidance.

At one sampling station (Event 143), the MOCNESS net was closed prematurely at 67.5 m, such that the interval 67.5 to 5 m was not sampled. In this instance, a vertical Bongo net (opening mouth diameter 18 cm, mesh size 53 µm) was used to sample this upper most depth interval. Volume sampled was obtained through multiplying the mouth area by the vertical distance sampled (70 m) and the sample processed as described above to determine abundance per taxa in units of individuals m-3.

Data collection:

1. A MOCNESS net system (1m2 mouth diameter, 330 micrometer meshes) and 1 deployment of a mini Bongo (18 cm diameter 53 micrometer mesh)

2. Sample splitting apparatus

3. Binocular light microscope

Data quality:

All species were identified according to the taxonomic guides available at time of analysis and the user must be aware that some species names may have since been updated.

The value 0 represents an instance where the taxon was actively looked for but no specimens were present in the sample.