Authors: Smith, J., Riddle, M.J., Post, A.L., Beaman, R.J., Rintoul, S.R., De Santis, L., O’Brien, P.E.
Publication: 11th International Symposium on Antarctic Earth Sciences, 10-15 July 2011. Scientific Committee on Antarctic Research (SCAR), Edinburgh, U.K.
Dense hydrocoral-sponge communities have been identified on the upper continental slope of George V Land, East Antarctica and in 2008 were declared Vulnerable Marine Ecosystems by the Commission for the Conservation of Antarctic Marine Living Resources. Analysis of physical and biological datasets collected during the 2007/08 CEAMARC survey identified that the richest communities are found in the heads of canyons which receive Antarctic Bottom Water formed on the George V shelf, and the canyons harbouring rich benthos are also those that cut the shelf break. This led to several hypotheses regarding their distribution and three main factors were identified: 1) their depth in relation to iceberg scouring; 2) the flow of organic-rich bottom waters; and 3) their location at the head of shelf cutting canyons.
These hypotheses were tested during a recent marine science voyage in January 2011 to the same region. Several sites along the continental slope were photographed to identify the presence or absence of hydrocoral-sponge communities. The sites were chosen within two broad areas thought to be receiving, and not receiving, Antarctic Bottom Water. Additionally, within these areas, sites were chosen to include canyons and interfluves. Oceanographic data collected during the voyage provides evidence of descending plumes of Antarctic Bottom Water across the Adélie Sill. Dense hydrocoral-sponge communities were identified in this area, adjacent to the communities previously identified in Jussieu Canyon. In Cuvier Canyon, further to the west, only sparse hydrocorals were identified, despite dense hydrocoral-sponge communities being identified here previously, suggesting their distribution may be very localised. There were no hydrocorals identified in areas where there was no bottom water flow. There is evidence of some bottom water flow at sites on the upper slope east of Mertz Bank and sparse hydrocoral communities were found at two sites in this area.
Initial analysis of the new data supports the hypotheses regarding the physical controls on hydrocoral-sponge community distribution, and will enable better targeting of other areas on the Antarctic continental shelf and slope where fragile communities that may warrant protection as Vulnerable Marine Ecosystems may be encountered.