In 1985 a unique assemblage of calcareous tube-building polychaete worms, Serpula narconensis, was discovered in Ellis Fjord in the Vestfold Hills in east Antarctica. These form an almost continuous aggregation of tubes comprising a biogenic reef structure 1.5 m high, encompassing the seabed from 5 to 30 m, and estimated to be 8 km in lateral extent around the fjord mouth. This reef structure supports very high abundances of other organisms such as urchins, holothurians, crinoids, and a diverse array of sponges, ascidians and mobile fauna such as crustaceans, gastropods and fish. In 2019 some of the sites were resurveyed to examine changes in community composition and abundances over this period. There is strong evidence of significant long term changes in this unique community. We predict that this ecosystem has a high degree of vulnerability to environmental change and is worthy of consideration for protected status in the form of an Antarctic Specially Protected Area (ASPA). Currently there are very few coastal marine ASPAs and their designation is complicated by a slow process and differing national agendas. This study highlights the potential vulnerability of Antarctic coastal ecosystems and the need for a comprehensive and representative system of protected areas.