Living (stained) and dead foraminifera from the newly ice-free Larsen Ice Shelf, Weddell Sea, Antarctica: ecology and taphonomy
Within the past 7 years, the northern Larsen Ice Shelf has broken up so it is now possible to sample the sea floor that formerly lay beneath it. Box cores have yielded surface sediment samples (0-1 cm) that give information on living and dead foraminiferal assemblages. The living assemblages are of moderate diversity and four have >50% calcareous tests while five have >50% agglutinated tests. This is an area of high primary production and the standing crops of the benthic foraminiferal assemblages are high. All the dead assemblages are much enriched in agglutinated tests, often >90%. They give a time-averaged record of the past 7 ice-free years and several decades of ice cover. The loss of permanent ice cover (there is still seasonal ice cover) may have caused some response from the fauna, but it is likely that it was mainly changes in relative/absolute abundance of the existing fauna. The differences between the live and dead assemblages in the surface 1 cm are attributed mainly to taphonomic effects: dissolution of calcareous tests and loss of fragile agglutinated tests. Subsurface samples down to 5 cm show that dissolution of calcareous tests is widespread and there may be some loss of fragile agglutinated forms such as Reophax subdentaliniformis. For these reasons, in this area, it may be best to make palaeoecological interpretations on the agglutinated component of the fossil assemblages.