23 January 2008Back to sciencePolarstern ANT–XXIV–2 — weekly report 7
We are heading north on the Greenwich meridian, happy to be back to scientific work after completing our logistic tasks. At the productive zone on the ice edge we enjoyed the sight of whales, blowing and breaching. They came so close to the ship that we could hear them breathing. We are reviewing our biodiversity results in the context of the physical data and the energy flux from surface to seafloor. Our final station will revisit the 52° S site that we sampled on 6 December, to see if the benthos has changed after the phytoplankton bloom.
The samples collected are rich in species and in diversity within faunal groups. For example, in the molluscs we found 66 species (5 new to science) in over 1,000 individuals; most were bivalves from Maud Rise, in high densities of over 300 per m². Nils Brenke deployed a video camera at 2,150 m in the area, revealing a fish above the fine sediment of the seafloor.
SYSTCO leader Angelika Brandt reported that peracarid (brooding) crustaceans made up about 20% by numbers of specimens from most of the epibenthic sledge samples; over half were isopods, representing at least 15 families. Subsequent results of fatty acids and stomach analysis will tell us about their trophic position.
While sorting the samples, we made some important discoveries. Among the molluscs Michael Schrödl found the rare monoplacophoran Laevipilina antarctica. The live specimen, 1 mm long, will hopefully yield undamaged genetic material. A genomic analysis could hold a clue to the unfolding story of the phylogenetic origin of this 'living fossil' representing one of the last animal classes with minimal information to date. Tiny molluscs were found in some astonishing places — as parasites on sea cucumbers and as commensals on ascidians.
The search for foraminifera yielded a rich fauna: 99 species representing all four classes; in total over 3,000 specimens. Forams were a dominant component of some sediment samples and may provide a link to the production in surface waters. There were 93 potential specimens of the mysterious komokiaceans, found mainly in abyssal polar regions; a group of uncertain evolution that was recently found to be close to foraminiferans.
The sponge fauna included 40 species and about 400 specimens. Most sponges filter tiny particles from the water but some unusual species are predatory on animals such as crustaceans. Dorte Janussen discovered some examples: Chondrocladia sp. trawled from 2,180 mand Cladorhiza sp. from 5,335 m. Another group of filter feeders, the colourful cnidarians, thrived especially at a deep shelf station.
We farewell the sea of ice and its awesome creatures. As we travel north, we welcome the moist air…and a few hours of darkness each night.
Victoria Wadley
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