Distribution of hydrocorals along the George V Slope, East Antarctica

Abstract

Dense coral–sponge communities on the upper continental slope (570–950 m) off George V Land, east Antarctica, have been identified as Vulnerable Marine Ecosystems. We propose three main factors governing their distribution on this margin: (i) their depth in relation to iceberg scouring, (ii) the flow of organic-rich bottom waters, and (iii) their location at the head of shelf-cutting canyons. Icebergs scour to depths of 500m in this region, and the lack of such disturbance is a likely factor allowing the growth of rich benthic ecosystems. In addition, the richest communities are found in the heads of canyons that receive descending plumes of Antarctic bottom water formed on the George V shelf, which could entrain abundant food for the benthos. The canyons harboring rich benthos are also those that cut the shelf break. Such canyons are known sites of high productivity in other areas due to strong current flow and increased mixing with shelf waters, and the abrupt, complex topography.