Sophie Fielding 

British Antarctic Survey

South Georgia

Polar Ocean Ecosystem Time Series – Western Core Box

Cruise DY098 is the 23rd occupation of the Polar Ocean Ecosystem Time Series Western Core Box (POETS-WCB). The main deliverable of the POETS-WCB is a consistent unique time series of mesoscale distribution and abundance of Antarctic krill and an understanding of their physical environment within the region of South Georgia, South Atlantic (1996 – current). These data are required to understand the long-term variability in krill biomass at South Georgia and the influences from climatic variability, fishing pressure and predation.

South Georgia is an area of high regional biodiversity, supporting large numbers of endemic and range-edge species. The pelagic ecosystem in this region is extremely productive with intense phytoplankton blooms supporting a rich food web that includes zooplankton, in particular large densities of Antarctic krill, and vertebrate predators (penguins, seals and whales).

The British Antarctic Survey (BAS) have undertaken cruises to monitor krill biomass as part of the ongoing assessment of the status of the marine ecosystem in the south-west Atlantic sector of the Southern Ocean. In addition to an annual acoustic assessment of krill in an area to the north-west of South Georgia called the Western Core Box (WCB), BAS maintains moorings both on the South Georgia shelf and in the open ocean region of the Scotia Sea. The open ocean sustained observations in the area are carried out as part of the SCOOBIES (SCotia sea Open-Ocean BIological laboratoriES) programme, a NERC National Capability Science (Single) funding (NC-SS) project with a primary purpose to consider the flux of carbon to deep ocean layers as well as monitoring ocean chemistry parameters, particular in relation to ocean acidification. This moored instrumentation complements the WCB surveys by providing year round temporal sampling of environmental conditions and acoustic backscatter. 

The cruise consists of the following:

POETS - WCB survey

1. Acoustic survey during daylight hours using multi-frequency (38, 70, 120 & 200 kHz) Simrad EK60 echosounder. Two transects to be run each day during a four day period.

2. Regular deployments of XBTs (Expendable bathythermographs) along transects during day.

3. Deployment of the CTD at minimum of two stations per night during survey.

4. Continuous operation of underway data logging system (bathymetry, location, sea surface temperature, sea currents, etc.).

5. Net sampling (RMT8 and other zooplankton/micronekton nets) at night-time stations plus target fishing during both night and day to ground-truth acoustic data.

6. Acoustic calibration using standard sphere techniques will be undertaken in one of the deep-water harbours on the North coast of South Georgia (Stromness Harbour is the preferred location).

7. Recover WCB mooring. Download data, refurbish and replace batteries. Redeploy mooring.

POETS – SCOOBIES (SCotia sea Open-Ocean BIological laboratoriES)

Mooring recovery, refurbishment and redeployment

1. Recover two deep-water moorings (SW and NW of South Georgia). Download data, refurbish and replace batteries. Redeploy moorings during cruise.

2. Net sampling (RMT8, MOCNESS and other zooplankton nets) over 24 hour periods at mooring stations.

There are berths available for collaborative projects that can be undertaken within the existing sampling schedule. Funding for these can be sought from the Collaborative Antarctic Science Scheme.