A Murky Detour.

Modus satellite image of algal bloom.

For some weeks an algal bloom had been observed near the Mawson coast from satellite images. The ship was directed to transit the bloom a number of times and biologists Susan, Julie and Josh on board the ship were rostered to conduct sampling so that the algae could be identified.

Algal bloom and pancake ice

The bloom was estimated to be around 200 km wide and 100 km long, and, while scientists aren’t exactly sure what caused the bloom, one theory is that it was caused by recent summer winds blowing iron off of the Antarctic continent. The iron acts as nutrient for what is thought to be phaeocystis algae. The bloom will benefit most of the food chain attracting predators chasing the smaller species that feed off the algae such as krill and other zoo plankton. The bloom should provide a bounty for penguins, seals and whales that will feed on the fish or the krill itself.

Algal bloom and pancake ice

The surface water colour was brownish when the ship encountered the bloom. A dirty brown scum was evident between the pancake ice on the water surface.

At designated 3 hour intervals over about 36 hours water samples were collected and then through filtering and centrifuge the algal samples were collected and preserved in vials for later analysis. Fluorescence, water temperature and salinity were also monitored.

Filtering

Preparing for centrifuge

Centrifuge

Concentrated algae sample

Monitoring while passing through bloom.

After completion of the algal sampling krill was collected from open water. This involved stopping the ship and using a special net to catch the krill. The resulting catch was kept in darkness in special tanks with fresh seawater constantly circulated through the tanks to ensure adequate oxygen supply. Any dead krill were removed each day to prevent fouling of the tanks.

Krill are about 2cm long and become orange when stressed.

The krill kept in darkness and without food are able to survive the journey back to Australia as they have the ability to be able to consume their own body mass, growing new shell for the smaller body as required.

Krill in tanks on board the AA.

Once the Derwent River estuary was entered the external water intakes to the krill tanks were closed. Estuary water is not suitable for krill as it contains fresh water.  Once fresh seawater is no longer available the krill need to be removed from the ship to the Antarctic Division Kingston facility within 6 hours before oxygen depletion in the water occurs. 

Special arrangements were made for their unloading from the refueling wharf at Selfs Point, Hobart when the ship docked..