Biogenic hydrocarbons in the particulate material of the water column of the Bellingshausen Sea, Antarctica, in the region of the marginal ice zone

The biogenic hydrocarbon content of particulate matter of the Bellingshausen Sea in the region of the marginal ice zone (MIZ) has been used to investigate the origins and fates of organic material in the water column in the region of a marginal ice zone. Particulates were sampled from four depths to 200 m in pack ice and at the ice edge, and from seven depths to 3000 m in open ocean. Total n-alkane concentrations associated with particulates increased from 200 ng l−1 under the pack ice to 1000 ng l−1 in the open ocean, and decreased with depth in open water to 15 ng l−1 at 3000 m. The influence of phytoplankton on particulate material was shown to be negligible under the ice but extended horizontally and vertically as the ice edge retreated. Sea-ice algae did not appear to seed the phytoplankton growth under the ice or the subsequent “bloom” at the MIZ. The alkane signature of phytoplankton from the MIZ bloom was detected at a depth of 200 m near the ice edge, at 500 m in open sea, and in surface sediments (4100 m). Zooplankton biomarkers that were at low levels in krill under the ice were higher in animals from the open ocean but were not detected in the water column or sediments. It was concluded that the majority of particulate material in the water column was algal in origin. Material in the surface sediment from under pack ice probably originated from a deep-living winter population of copepods and material in surface sediment from the ice-free ocean originated from the algal “bloom” at the MIZ.

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