Nella Dan: AAMBER Cruise - Zooplankton and Krill data

Brief description

This data were collected on the sixth Nella Dan voyage of a long term field survey project being conducted by the Australian Antarctic Division, to collect distribution, abundance and population structure data for the krill Euphausia superba in the Prydz Bay region, Antarctica.

This voyage, the Australian Antarctic Marine Biological Ecosystem Research 1986/1987 (AAMBER 86/87) cruise, operated between February and April 1987. During March, a survey of the krill population and zooplankton community was conducted, to determine the late summer distribution and abundance of krill, especially the larvae. This was done as a follow up to SIBEX II in mid-summer (Janurary) 1985. The major species investigated were Euphausia superba, Euphausia frigidia, Euphausia crystallorophias and Thysanoessa marcuria. Phytoplankton pigment analysis was also conducted at each CTD station site.

Lineage

Progress Code: completed

Statement: This voyage is one of six which studied the abundance and disribution of Euphausia superba. This provided a good coverage of the area at varying season times and conditions. There are some differences in sampling sites due to logistical constraints and weather conditions.

Data collection: A Rectangular Midwater Trawl (RMT 1+8) was used for the collection of larval and post larval (juvenile and adult) krill Euphausia superba, and other zooplankton. Three haul methods were used. At each station a shallow downward oblique haul was taken from the surface to 200m. At selected stations a deep downward oblique haul from 200m to 1000m was taken to collect early developmental stages of Euphausia superba. When krill swarms were located at particular depths (by a Simrad EK 120 echosounder), specific aimed horizontal tows were made.

On-ship processing: This included removing specimens of Euphausia superba and other large and fragile zooplankton from the catch. All specimens were preserved in Steedman's solution until examination at the Antarctic Division laboratories. Krill swarm catches were weighed using a spring balance, and part of the catch (greater than 200 specimens) were preserved in Steedman's solution.

Post-ship processing:
This included classification of the RMT 8 post-larval krill into juvenile, male and female maturation stages, using the Makarov and Denys (1981) system. The body length (using a slide caliper) and body wet weight (using an electronic top-pan balance) were measured for each RMT 8 specimen. Non-krill zooplankton in the RMT 8 samples were identified, weighed and counted. The RMT 1 catches were sorted to separate the Euphausia superba larvae and other euphausiid species larvae from the remaining zooplankton. The euphausiid larvae were classified into developmental stages and counted under a dissecting microscope. Data are logically consistent, as oceanographic data (CTD measurements) and water collections for phytoplankton pigment analysis were also obtained at the same sampling sites as the krill and zooplankton hauls. A cruise track showing the sampling sites in available in: Hosie G. et al. (1991) AAMBER 86/87 cruise krill/zooplankton sampling data. Australian National Antarctic Research Expedition Research Notes 79.