Nella Dan: ADBEX I Cruise - Zooplankton data

Brief description

This dataset contains results from the Antarctic Division Biomass Experiment (ADBEX I) cruise of the Nella Dan. This cruise is the second in a series of six cruises, and follows the First International BIOMASS Experiment (FIBEX) in early 1981, documentation of which can be found in ANARE Research Notes 7, or by searching the metadata records for FIBEX. ADBEX I operated between November and December 1982, and studied the distribution and abundance of krill (Euphausia superba). Surveys of krill and other zooplankton were taken off Antarctica in the Australian sector (Mawson to Davis region) and Prydz Bay. The major species investigated were Euphausia superba, Euphausia frigidia, Euphausia crystallorophias and Thysanoessa marcuria. Other pteropods and cephalopods were also studied. Physical and chemical oceanography data were also obtained at some stations, as well as phytoplankton samples. Summary results are listed in the documentation.

Lineage

Progress Code: completed

Statement: The cruise track was followed as closely as weather and ice conditions would allow. The stations provide a fairly complete coverage. This cruise is the second in a series of six cruises, providing a good coverage of the area over different seasons and conditions. Data collection: Three types of nets were used for taking zooplankton samples. A standard Rectangular midwater Trawl net (RMT 8) was used to complete fifty stations, with a mouth area of 8 square metres and a mesh size of 4.5mm. At stations 2 to 10 and 42 to 50, oblique tows with bongo nets were made. The two bongo nets used had a square mouth of 500mm each side and a mesh size of 1mm. At three stations, an International Young Gadoid Pelagic Trawl net (IYGPT) was used to take hauls to establish whether the RMT nets were sampling the full size range of Euphausia superba. Station 41 was occupied for 27 hours to determine the vertical distribution of Euphasia superba over a daily cycle. Stations were taken during the morning, afternoon and as close as possible to midnight.

Ship-board processing: The entire catch was weighed as accurately as possible immediately it was brought onboard, and large zooplankton (eg. medusae) were also weighed individually. Euphausia superba was sorted from the catch and the remainder sorted into major groups, eg. pteropods, copepods, fish, etc. and preserved. A random sample of at least 200 Euphausia superba were measured and sorted for sex and maturity stage and preserved. The remainder of the Euphausia superba was then frozen or preserved.

Post-ship processing: The catches were sorted into individual species, weighed and counted. Different nets were used to establish consistency and eliminate bias to a particular size or type of specimen. Physical and chemical oceanography was also recorded at a number of stations, providing consistency between the oceanography and biology data. Stations were taken during the morning, afternoon and as close as possible to midnight. Some stations near the beginning of the season were not able to be taken due to difficulties with pack ice. The cruise track was established at the beginning of the expedition to eliminate any bias.