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AGU: Paleoceanography

 

Keywords

  • Amery Ice Shelf
  • hot water drill
  • borehole video
  • benthic assemblage
  • sediment record
  • Antarctica

Index Terms

  • Biogeosciences: Benthic processes (4804)
  • Biogeosciences: Biosignatures and proxies
  • Biogeosciences: Life in extreme environments
  • Cryosphere: Ice shelves
  • Geographic Location: Antarctica (4207)

Abstract

PALEOCEANOGRAPHY, VOL. 22, PA1204, 8 PP., 2007
doi:10.1029/2006PA001327

A diverse benthic assemblage 100 km from open water under the Amery Ice Shelf, Antarctica

M. J. Riddle

Australian Government Antarctic Division, Kingston, Tasmania, Australia

M. Craven

Australian Government Antarctic Division and Antarctic Climate and Ecosystems Cooperative Research Centre, Hobart, Tasmania, Australia

P. M. Goldsworthy

Australian Government Antarctic Division, Kingston, Tasmania, Australia

F. Carsey

California Institute of Technology, Jet Propulsion Laboratory, Pasadena, California, USA

A hot water drill was used to penetrate 480 m of ice to reveal a diverse benthic assemblage, dominated by suspension-feeding invertebrates, under the Amery Ice Shelf (East Antarctica) at a location 100 km from open water and at a depth of 775 m below sea level (840 m below the ice shelf surface). This is the first record of a benthic assemblage of this type found at this distance under an ice shelf. The few previous reports of life under ice shelves describe assemblages with very different trophic strategies (e.g., sparse assemblages of mobile scavengers or chemotrophs) or are in circumstances in which in situ photosynthesis at tide cracks or through the ice cannot be ruled out as a potential source of primary production. The physical characteristics of the Amery Ice Shelf and the feeding strategies represented together indicate that the only likely source of primary production to sustain the benthic assemblage is material advected from open water. This suggestion is supported by observed current speeds in the vicinity and reported rates of particle settling. The observation under an ice shelf of a benthic assemblage that is very similar to those found elsewhere in Antarctica, in locations dominated by annual sea ice or at depths below the photic zone, has implications for the interpretation of sediment paleorecords to represent the history of ice shelf advance and retreat. Without observations of this living assemblage in situ, the remnants of its component species in the sediment record, such as sponge spicules, echinoderm ossicles, and bryozoan fragments, could be interpreted reasonably, but erroneously, to represent open water conditions.

Received 24 May 2006; accepted 19 September 2006; published 23 January 2007.

Citation: Riddle, M. J., M. Craven, P. M. Goldsworthy, and F. Carsey (2007), A diverse benthic assemblage 100 km from open water under the Amery Ice Shelf, Antarctica, Paleoceanography, 22, PA1204, doi:10.1029/2006PA001327.

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