Diatom valve distribution and sedimentary fatty acid composition in Larsen Bay, Eastern Antarctica Peninsula

During austral summer 2006–2007, five sediment cores were recovered from the Eastern Antarctic Peninsula (EAP) continental shelf. Microscopic observations and sediment fatty acid (FA) composition analyses were carried out to investigate whether the drastic changes at the sea surface in EAP may be reflected in the sedimentary record. A sharp decrease in the number of diatom valves was observed below 2 cm depth. This difference between the upper 2 cm of sediment and the deeper part of the sediment column was attributed to the drastic change in the upper water column conditions after the collapse of the ice shelves, which allowed the arrival of phytoplankton debris and fresh organic matter to the sea floor in EAP. The presence of bacterial-, zooplankton- and detrital-related FA throughout EAP cores suggests that there has been an input of older and more refractory organic matter into the region, presumably by lateral transport before the Larsen ice shelves disintegration.

► Sediments were studied to see if changes in the water column were reflected in seabed sediments.
► Sediments off the Northern and the Eastern Antarctic Peninsula were compared.
► 2 Ice shelf collapses in 1995 and 2002 affected the Eastern Antarctic Peninsula.
► The lability of the organic matter was higher in the Northern than in the Eastern Antarctic Peninsula.
► Diatom valves were deposited only after the collapse of the ice shelves.