12 December 2007

Polarstern ANT-XXIV-2

New methods of seafloor sampling for Antarctic marine life

The busy deck of the Polarstern. Photo: V. Wadley

The current voyage Polarstern 24-2 brings together 3 projects on Antarctic ecosystems and their physical environment:

• Census of Antarctic Marine Life (CAML) studies the biodiversity, abundance and distribution of marine species, from microbes to whales
• Antarctic Deep–sea ecosystem (ANDEEP — SYSTCO) studies life on the abyssal seafloor, linking it to productivity in the waters above
• Synoptic Circum-Antarctic Climate and Ecosystem Study (SCACE) connects the oceanography and climate to the ecosystem, for comparison with future changes

Antarctic biodiversity studies have some special challenges — sampling under ice, in remote locations and in habitats with extremely low temperatures. Equipment includes some bizarre contraptions, such as a net that scrapes up the animals under pack ice. This Surface and Under-Ice Trawl (SUIT) is the brainchild of a Netherlands team.

Trawled behind the ship, the SUIT has

• a one-tonne weight on its towing cable, to sink it beneath the ice
• wheels help it move over the uneven ridges under the ice
• an overflow ejects any iceblocks that get into the net

The catch includes krill, amphipods, squid and fish. The productive under-ice habitat, only recently explored, is vulnerable to climate change.

The Alfred Wegener Institute (AWI) for Polar and Marine research coordinates polar research in Germany. They provide infrastructure such as the Polarstern and the Antarctic and Arctic stations. Our mission includes transporting materials for a new building at the Antarctic base, Neumayer. A helicopter will transport the containers from ship to shore. The scientists onboard have been quick to piggyback the test flights for predator surveys. Along with hours of observations from the freezing deck, they measure the changing populations of predators such as birds and seals.

Biodiversity studies in Antarctic waters include up to 7,000 species of invertebrates and mammals. These are the species described already — there are another 4,000 species on the workbench. And we have just started on assessing the diversity of microbes! CAML is coordinating biodiversity studies on 18 research vessels during the International Polar Year (IPY).

Scientists send their geo-referenced species data to the Antarctic dataportal, SCAR-MarBIN so that everyone can share results. The dataportal has facilities for analysis and visualisation of data trends, to encourage the integration of various collections during the IPY. To bring the results to a wide audience, Equipe Cousteau works on Education and Outreach for the projects.

Ophiuroid Photo: C. Brandt

On 3 December at 47° South, wedged between two big storms, the onboard weather guys selected reasonable conditions for our first sampling station on 5 December at about 52° South and 0° West in water depth of 3,000 meters. Daylight hours have increased noticeably — hauling gear on the deck at 4 am enjoyed plenty of natural light. An impressive array of sampling gear was utilised

• the Conductivity Temperature Depth (CTD) recorder
• underway acoustics and measurements of inorganic carbon, total alkalinity, oxygen and nutrients in the seawater
• bottom water sampler
• amphipod trap
• five different types of trawl
• epibenthic sledge; underwater camera
• geochemical sediment profiler; sediment multicorer
• plus a box corer to sample the seafloor

Victoria Wadley on the Polarstern 24-2 voyage. Photo: Feij

We found a variety of animals on the seafloor and in the water — copepods, krill, holothurians, ophiuroids, asteroids, anemones, isopods, amphipods, squid and fish. The seafloor was a fine sediment, sticky with organic ooze. Microscopic inspection of the mud revealed many foraminiferans — the same species found in an earlier bloom of phytoplankton at the water surface. Discoveries like this are the stuff of understanding the coupling of processes on the seafloor and in the ocean above — the rationale for our expedition.

Victoria Wadley
Census of Antarctic Marine Life and Australian Antarctic Division

12 December 2007 [PDF] - full report