Houtman Abrolhos
The Houtman Abrolhos is unusual in having a luxuriant and diverse living coral reef at such a high latitude. 194 species in 50 genera have been recorded there, all but two of which are tropical. This is a surprisingly high coral diversity, considering the high latitude of the reef, and the relatively low diversity of other biota. For a full list, see list of corals of the Houtman Abrolhos.
Houtman Abrolhos
The Houtman Abrolhos maintains a breeding population of Australian sea lions ("Neophoca cinerea"), probably numbering between 75 and 100. Historical data suggests numbers were previously much higher; for example, in 1727 survivors of the "Zeewyk" shipwreck killed over 150 sea lions in the Southern Group alone. This has led to a 1727 population estimate of between 290 and 580 animals for the entire Houtman Abrolhos. Populations apparently fell dramatically between the 1840s and the 1880s, largely due to extensive commercial sealing in the area. In addition to direct killing of the animals, it is likely that much of the mangrove habitat on the islands was cleared as fuel for trypots, and this may have affected the survival of young pups. Populations are thought to have been fairly stable for the last fifty years, although the lack of genetic diversity in the smaller population remains of concern, as does climate change.