DOI: 10.5285/f8058937-5b63-49a1-b445-cf60707b8b65
title: Epi- and mesopelagic mesozooplankton depth-discrete distribution and abundance across Polar Frontal Zone in Southern Ocean Atlantic sector

description: Mesozooplankton were collected with a MOCNESS net system during the oceanographic cruise JR16003 (Dec 2016 to Jan 2017). 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 during the reascent to the surface. All catches were immediately preserved in 4% buffered formaldehyde. Identification of taxa was performed by the Morski Institute (Poland). Specimens were categorised to the lowest possible taxonomic level, which, in some cases, encompassed developmental stages but, in other cases, was limited to higher order taxa. Each taxa was enumerated to determine abundance in units of individuals m-3. The dataset allows examination of the distribution and abundance of these species across Polar Frontal Zone in Southern Ocean Atlantic sector. The survey was funded by The UK Natural Environment Research Council (NERC) and carried out as part of the POETS Wester Core Box and SCOOBIES programmes at British Antarctic Survey. The time of Geraint Tarling and the analysis of the MOCNESS nets was funded by the NERC grant SeaDNA - Assessing marine biodiversity and structure using environmental DNA: from groundtruthing to food web structure and stability NE/N00616X/1 PI: Stefano Mariani.
description: 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.
description: 1. A MOCNESS net system (1m2 mouth diameter, 330 µm meshes) and 1 deployment of a mini Bongo (18 cm diameter 53 µm mesh) 2. Sample splitting apparatus 3. Binocular light microscope
description: 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.