Nella Dan: ADBEX II Cruise - Krill and Zooplankton data

Brief description

This dataset contains results from the Antarctic Division BIOMASS Experiment II (ADBEX II) cruise of the Nella Dan. This is the third cruise of six, and follows the ADBEX I cruise made during late 1982. ADBEX II was to have been an international experiment, Second International BIOMASS Experiment I (SIBEX I), in cooperation with Japan, South Africa and France, however due to the delay of a supply program Australia's participation was cancelled. ADBEX II is the result of a reduced sampling program carried out during the resupply of Davis and Mawson stations. Surveys of krill and other zooplankton were taken off Antarctica in the Australian sector (Mawson to Davis region) and Prydz Bay in January 1984. Species identity and abundance data were obtained. The major species investigated were Euphausia superba, Euphausia frigidia, Euphausia crystallorophias and Thysanoessa marcuria. Other pteropods and cephalopods were also studied. Results from hydroacoustic surveys of krill biomass were also obtained, as well as CTD and chlorophyll data. Summary results are listed in the documentation.

Lineage

Progress Code: completed

Statement: The stations provide a fairly complete coverage. This cruise is the third in a series of six cruises, providing a good coverage of the area over different seasons and conditions. This cruise was to have been a more detailed experiment in collaboration with Japan, South Africa and France. Due to resupply problems, sampling had to be reduced.

Data collection: Two methods were used for sample collection. A rectangular midwater trawl net (RMT8) was used for the collection of juvenile and adult krill, Euphausia superba. Horizontal tows were also made were krill swarms were located using a Simrad EK 120 echo-sounder. Oblique tows using bongo nets were used to collect krill larvae.

Ship-board processing: The large and fragile zooplankton were initially separated from the rest of the specimens, and all specimens were preserved in Steedman's solution. Krill catches from swarms were weighed using a clock-faced spring balance, and part of the catches (greater than 200 specimens) were preserved in Steedman's solution.

Post-ship processing: The RMT8 krill samples were sorted into juvenile, male and female, and body length (using a slide caliper) and body wet weight (using a Mettler top-pan balance) were measured. Male and female Krill were further classified into maturation stages according to the system of Makarov and Denys (1981). Non-krill zooplankton in the RMT8 samples were identified to species to the lowest possible taxonomic level. Specimens of juvenile and adult krill were collected using the bongo net. These specimens were used to obtain supplementary body length and maturation stage data, but not for quantitative calculation of biomass or density. Euphausiid larvae were sorted from the bongo net samples, and identification was based on Makarov (1980). The larvae of Euphausia superba and Euphausia crystallorophias raised from eggs in the laboratory were also used as a reference for identification. Logically consistent. 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. Euphausia superba and Euphausia crystallorophias larvae raised from eggs in the laboratory were used as a reference for catch larvae identification, as well as published material. Data was collected during a supply cruise to the Australian stations Davis and Mawson, and hence it is likely that sampling stations were taken fairly opportunistically, and not always at the best locations.