Ship based sampling

Water samples containing microbes are collected either using instruments deployed over the side of the ship or from a seawater supply line with an intake at seven metres depth in the ship’s hull.

Samples for depth profiles are obtained using a rosette sampler. The rosette has 24 x 10 litre Niskin bottles that can be closed at required depths by electronic signal from the ship. The attached CTD (Conductivity, Temperature, and Depth) system collects continuous data, profiling the water column’s temperature, salinity and density. Water masses, oceanographic features and currents are identified from these data.

Samples for phytoplankton pigment analysis (0.5 — 2 L) are filtered onto glass fibre filters and stored in liquid nitrogen (-196°C) for analysis on return to Australia.

Duplicate samples are preserved for cell identification by light microscopy or electron microscopy, and cell counting by a process of sedimentation and inverted microscopy. Living cells are also examined and counted whilst on board the ship, with shock-mounted microscopes to avoid vibrations from the ship’s engines.

Bacteria and viruses are filtered onto black polycarbonate membrane filters, stained with dyes that bind to their DNA and RNA, and counted by fluorescence microscopy.

Large phytoplankton are collected using 20 micrometer mesh plankton nets. This method of sampling is selective but it allows comparisons of current phytoplankton communities with historic samples.

Sea ice sampling

It is difficult to sample the microbial community living within sea-ice. The protists live in brine channels that are formed between relatively fresh water ice crystals. To protect the delicate organisms, sampling and laboratory techniques must avoid large changes in salinity that occur during melting.

Ice communities are sampled using an ice corer or Jiffy drill. The ice corer provides a cylindrical section of the sea-ice from which samples are cut, melted in filtered seawater and examined for microbes.

Alternatively, a partial core hole is drilled and the microbe-containing brine is allowed to drain into it.

Land-based sampling

Over-snow vehicles or small boats are used to get to collecting sites from our Antarctic stations. Sea ice and water samples are brought back to the laboratory where there are low-temperature incubation tanks, culturing facilities and analytical equipment.

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