Physical Controls on Deep Water Coral Communities on the George V Land Slope, East Antarctica

Dense coral-sponge communities on the upper continental slope at 570 - 950 m off George V Land have been identified as a Vulnerable Marine Ecosystem in the Antarctic. The challenge is now to understand their likely distribution. Based on results from the Collaborative East Antarctic Marine Census survey of 2007/2008, we propose some hypotheses to explain their distribution. Icebergs scour to 500 m in this region and the lack of such disturbance is probably a factor allowing growth of rich benthic ecosystems. In addition, the richest communities are found in the heads of canyons. Two possible oceanographic mechanisms may link abundant filter feeder communities and canyon heads. The canyons in which they occur receive descending plumes of Antarctic Bottom Water formed on the George V shelf and these water masses could entrain abundant food for the benthos. Another possibility is that the canyons harbouring rich benthos are those that cut the shelf break. Such canyons are known sites of high productivity in other areas because of a number of oceanographic factors, including strong current flow and increased mixing with shelf waters, and the abrupt, complex topography. These hypotheses provide a framework for the identification of areas where there is a higher likelihood of encountering these Vulnerable Marine Ecosystems.

乔治五世海岸外570至950米水深的大陆坡上部区域的密集珊瑚-海绵群落，已被认定为南极地区的脆弱海洋生态系统（Vulnerable Marine Ecosystem）。当前的研究难点在于明确该类群落的潜在分布范围。基于2007/2008年东南极海洋联合普查（Collaborative East Antarctic Marine Census）的调查结果，我们提出了若干用以解释其分布规律的假说。该区域内冰山的底切冲刷作用可达500米水深，未受此类扰动的区域或是促成丰富底栖生态系统发育的关键因素之一。此外，群落覆盖最为密集的区域均分布于峡谷头部。存在两种潜在的海洋学机制，可解释滤食性生物群落的繁盛与峡谷头部之间的关联。这些群落所在的峡谷，承接了乔治五世陆架上形成的南极底层水（Antarctic Bottom Water）下沉羽流，该水团可为底栖生物提供充足的食物来源。另一可能性为，孕育丰富底栖生物的峡谷均为切穿陆架坡折的峡谷。这类峡谷在其他海域已是公认的高生产力区域，其成因涵盖多项海洋学因素：强劲的洋流、与陆架水的混合作用增强，以及陡峭复杂的地形。上述假说可为识别更有可能存在此类脆弱海洋生态系统的区域提供研究框架。