Where the Great Barrier Reef's already tropical waters are heating up quickly (sometimes reaching 35 degrees centigrade), Sydney's slowly warming and previously-temperate waters are becoming increasingly biodiverse. At least four types of hard and branching corals have been identified in Sydney's Northern Beaches, including the "Pocillopora aliciae;" a species which Marine Ecologist and University Professor Douglas Booth observes had only been recorded in Port Stephens, which is approximately 120km to the north. This is the furthest recorded southern migration of any tropical coral species, which is due possibly to the strength of the East Australian Current, which is driving species southwards along the east coast. These branching corals are providing habitats for a range of marine species also typically found much further north, such as trapezia crabs, tropical gobies and multiple species of damselfish. The combined arrival of non-native coral and marine species demonstrates how the poleward migration of tropical coral has the potential to alter marine environments and their inhabitants. In much the same way, corals in Japan are fleeing northwards, according to a recent study conducted by Hiroyo Yamana of the "Centre for Global Environmental Research" in Tsukuba, Japan; which tracked the movement of corals at 14km per year. Compared to the average rate of expansion for land-dwelling plants and animals, which is 1km per year, this is a relatively fast migration, one that would not even be seen in geological time. Of the nine different coral types which Yamano and his team had determined the location of colonies, they discovered that four had moved polewards over the past 100 years, and five had remained stable. Yamano notes, however, that the four which moved had been identified as "vulnerable" or "near threatened" by the International Union for Conservation of Nature since 1998. The speed of their migration is perhaps due to the poleward movement of ocean currents which run along the east coasts of Japan, and which have the capacity to carry coral polyps to "newly suitable areas for colonies or reefs." The poleward migration might be 'good news' for the survival of certain vulnerable coral species, but it is not necessarily a positive instalment for marine ecosystems as a whole. As the oceans surrounding South Africa warm in some areas and cool in others, many submarine plants and animals have been forced to relocate, which has brought about observable ecological change, and generated good reason for environmental concern. As the south-western coast environment cools, many marine organisms, such as "mussels, kelp, barnacles, crabs, rock lobsters, anchovy, sardines and sub-tropical fish,". have migrated towards to the warming eastern coast.