South Georgia & the South Sandwich Islands - Commemorative
Release Date - 9 November 2009
Corals of South Georgia and the South Sandwich Islands
When people think of corals they often picture the famed shallow water reefs that live in tropical waters. In fact there is a vast wealth of coral thriving in cooler and deeper waters all around the globe. Rather than relying on the sun and energy from symbiotic algae in their tentacles, as shallow water corals do, deep water corals waft their tentacles through the cool ocean waters sifting marine snow (organic particles made of dead organisms that fall from shallow waters) and zooplankton for sustenance. There are actually more coral species found in deep than shallow water though much less is known about their ecology, reproduction, or even where exactly they are found.
Most corals require hard or rocky seabed to attach to and the ample rocky seafloor and cool productive waters around Antarctica are ideal for this purpose. The seafloor surrounding South Georgia and the South Sandwich Islands seems to provide a particularly good habitat for corals to settle onto and the productive waters provide a rich food supply for growth. Consequently a wealth of coral has been recorded from these waters.
Deep-water corals are quite varied; black corals, hard corals, soft corals, lace corals and octocorals all live in deep water, some to depths of more than 5 km. Black corals, confusingly, tend to have bright orange or white polyps; they are so named as their skeleton is black. Hard corals have a solid calcium carbonate skeleton whereas soft corals have just small scales of calcium carbonate embedded in their tissues, making them very flexible. Lace corals, such as the one represented on the 90p stamp, are a type of hydroid with a hard skeleton and can look very similar to hard corals. Octocorals are defined by having polyps with eight (‘octo’ means eight) tentacles. In the deep water around Antarctica, families of octocorals tend to have polyps covered in plates of calcium carbonate and it is the structure and shape of these plates that define different species. Three unidentified octocoral species of the Thouarella and Paragorgia genera are represented in the 55p, 65p and £1.10 stamps. The difficult task of telling different species apart explains why the corals represented in this stamp set are without species names. Many new species of corals have been described from Antarctica in recent years and there are many more to come.