Remotely Operated Vehicles (ROVs) remain an efficient technology to uncover the secrets of Antarctic sea floor fauna. A video sequence at the foot of the Larsen B ice-shelf remnant reveals deep-sea sea cucumbers as abundant inhabitants.

ROVs have become standard non-invasive imaging tools for the Alfred Wegener Institute’s biological expeditions. For our expedition, devoted to the study of continental shelf sea floor communities (which were once under the now collapsed Larsen B ice-shelf), the ROV model Cherokee was selected (shown in the photo).

“Inspection ROVs like the Cherokee are fast to deploy and easy to recover” explains the marine ecologist Julian Gutt, who has 15 years ROV experience in Antarctic sea floor fauna investigation. Already used on a previous expedition, this 1.1m x 1.4m x 0.9m ROV carries one still- and three video cameras, including one for high-resolution video, as well as a manipulator that allows specimen collection. Werner Dimmler is one of Europe’s most experienced ROV pilots. “It can dive down to 1000m depth, which is enough for the Larsen B area,” he said.

The latest footage, taken right in front of the new glacier edge (after the 2002 ice-shelf collapse), showed a muddy bottom and occasional drop stones. It was a surprise to find such fine sediment so close to the glacier, in contrast with the nearly bare rocky bottom found two days ago. Here, the most abundant animals were two different species of holothurians, also known as sea-cucumbers.

“Holothurian species can have different diets, and these belong to the deposit-feeders type. They ingest mud to extract organic matter," explains Julian Gutt, also a sea-cucumber specialist. The bigger of the two species is known as a typical deep-sea species:



This makes it a good example of the “polar emergency hypothesis”, which states that deep-sea animals can ascend to shallow waters in both polar regions due to similar environmental conditions, especially the low temperature and unpredictable food availability. “The only place in this part of the Antarctic where we found this species was years ago at the edge of the huge Filchner-Ronne ice-shelf,” adds Julian Gutt. “This could be a first indication that deep-sea species are adapted to the extreme conditions found under an ice-shelf.”

Text: Gauthier Chapelle
1st photograph: Gauthier Chapelle (ROV)
2nd photograph: Julian Gutt (seabed)