IMIS

Sampling was conducted with BIONESS and WP2 net in 94 different sampling stations, mainly distributed in the Terra Nova Bay area, at the depth of 0-1000 meters. In terms of spatial coverage, this dataset covers 6027 distributional records that are also reported in terms of original abundance data (ind/m3) to allow a possible modelization of species distributions thanks to the availability of environmental variables that were collected together with the biological samples. The total of distributional records here reported has two different origins: 5306 are represented by bibliographic records obtained by digitizing the original data reports, whereas 721 correspond to physical museum vouchers, now curated by the Italian National Antarctic Museum (MNA, Section of Genoa). This group of museum samples comprises 8225 individual specimens, that were identified to the lowest possible taxonomic level. They belong to 4 orders, 25 families, 52 genera and 82 species, out of which 17 could be only determined at the genus level.
The study area covers a high portion of the northwestern Ross Sea, spanning from the Drygalski Ice Tongue in Terra Nova Bay to the continental slope surrounding the Central Basin. Some sampling stations exceed the Antarctic circle to reach the Balleny Islands and the northwestern stretch of sea.
Most samples composing this dataset were collected using a BIONESS, a zooplankton sampler consisting of multiple (usually ten) nets, stacked horizontally, that opened and closed, by an on-board operator, at desired depths while the instrument was towed by a vessel (ICES 2000). Due to the exceptional filtration to mouth area ratio (10:1), a 90% filtration efficiency can be reached for a clean net towed at 1.5 m s-1. Zooplankton samples are collected in dedicated cod-end numbered buckets for the subsequent handling and processing. During the PNRA expeditions environmental data were acquired by a multiparametric probe fixed on the BIONESS that recorded: temperature, salinity, depth, speed, in- and out-flow through the net, filtration efficiency and net number. Another sampling device employed during these PNRA activities was the WP2 (Working Party II) standardized net. This net had a 57 cm (0,25 m2) opening and length of 2,6 m which, combined with a 200/250 µm mesh width, offers high efficiency while performing vertical samplings of mesozooplankton (Fraser 1966, ICES 2000).