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In Sydney Harbour, rocky shores are usually flat or gently sloping sandstone platforms with low wave exposure and low tidal ranges. These intertidal habitats support a high number of species, which differ with height on the shore.
At lower shores, we usually find abundant foliose algae, along with tube-forming worms and/or sea squirts. Mid-shore
communities are generally dominated by Sydney rock oysters, limpets,
barnacles and encrusting algae.
Horizontal or gently sloping rocky intertidal habitats in the harbour are extremely important and support a high diversity of
organisms, including biogenic habitats such as oyster beds, turfing algae and tube worms.
Read more here about the intertidal rocky shores of Sydney Harbour in our review.
Natural subtidal reefs in the harbour support habitat-forming macroalgae (kelp) such as Ecklonia and Sargassum and most research to date has focused on these communities within the Middle harbour region. Ecklonia beds provide habitat for green, brown and red understorey algae, and invertebrates such as sea urchins, sponges, bryozoans, cnidarians, annelids, molluscs and crustaceans. Sargassum beds support diverse communities, particularly of small crustaceans such as isopods and amphipods.
These rocky reefs are hugey important for fish and support over 60% of the fish species recorded in Sydney Harbour.
On the open NSW coast, unvegetated areas, or 'barrens', are dominated by sea urchins, turbinid snails and limpets, which graze the hard and rocky bottoms and limit the growth of algae. These habitats are also present in Sydney Harbour but their ecology has yet to be explored.
Read more here about the subtidal reefs of Sydney Harbour.
Australian Museum collection records suggest that the harbour is highly diverse compared to other urbanised coastal regions in NSW. In addition, as these other locations have lower habitat
diversity than Sydney Harbour, it is likely that we have only documented a tiny proportion of the benthic biodiversity within the harbour.
For example, we know little of the sponges, bryozoans and cnidarians in the harbour, with perhaps hundreds of species yet to be found.
Read more here in our Sydney Harbour review.
Open water in Sydney Harbour covers around ten times the
area of rocky reefs, mangroves, and intertidal flats combined.
These open-water habitats are very important to ecosystem functioning in estuaries and bays as they allow the transport and dilution of nutrients and food particles, provide habitat for plankton and small fish, and act as corridors to allow movements of larger predators like fish, sharks and marine mammals.
Read more here about open-water habitats in our Sydney Harbour review.