Sydney builds underwater city for its marine inhabitants

An apartment with a view can set you back thousands of dollars per month in Sydney. But now crabs, starfish, snails and other local marine organisms are getting their own ‘rooms with a view’ with 60 specially designed underwater flowerpots installed onto the city’s seawall. Barbara Barkhausen reports from Sydney.

The Australian city of Sydney is creating new living spaces for its marine inhabitants in an effort to mitigate the negative impacts of caused by the development of the city’s harbour. (Image credit: City of Sydney)

The Australian city of Sydney is creating new living spaces for its marine inhabitants in an effort to mitigate the negative impacts of caused by the development of the city’s harbour. (Image credit: City of Sydney)

Sydney’s coastline has changed dramatically over the past 200 years. Where once stood rugged cliffs, mangrove swamps and beaches are today seawalls and high-rises built right up to the shoreline. Little remains of what the city looked like when the ships of the First Fleet carrying convicts from England arrived in Sydney harbour in 1788.

Harbour being revitalised

The city has undergone extensive urbanisation in the past few decades. But while this resulted in vibrant living spaces for the city’s land residents, its underwater inhabitants have been increasingly pushed out – with negative effects on the marine biodiversity.

This is now finally being addressed by the city. 60 underwater flowerpots have been installed on the city’s seawalls, which protect the city from flooding. Think of them as rooms with a view for Sydney’s marine inhabitants.

“Sydney Harbour is one of the world’s great harbours,” said Sydney mayor Clover Moore. The project will ensure that the harbour remains stunning both above and below the sea level, she added.

The project seeks to create an aquatic corridor for vulnerable marine life along the city’s seawall foreshore from the Glebe neighbourhood to Farm Cove and through the Elizabeth Bay.

28 new species

The city already tested the underwater flowerpot method back in 2014 in a project in nearby Blackwattle Bay. And with encouraging results: 28 new species were attracted to the marine installations, as was captured on underwater cameras.

Rebecca Morris, a marine ecologist at the University of Sydney who is leading the project, believes it can mitigate some of the negative impacts caused by the development of the Sydney harbour. And she hopes it can rehabilitate biodiversity in other regions “where natural shores have been replaced because of foreshore development.”

Artificial reef off Sydney

The Australian Haejoo Group knows a thing or two about underwater development. Reef designer Ryan Paik builds oversized skeletal structures – cubes, domes and pyramids – out of concrete and steel and then sinks them into the sea.

And like the flowerpots along the seawall, his underwater structures in Sydney’s harbour attracted algae, corals, barnacles, sponges and fish in just a few months’ time.

His special reef modules can be tailored to the needs of a region and the local marine life in terms of shape and size as each fish species has its own preferred shapes, voids, surfaces and profiles.

Apartment buildings for fish

Ryan Paik calls these structures “marine forests”. Others would say he is creating “apartment buildings” for fish. “The fish like the small voids in the structures, they feel comfortable there,” said Paik. “Artificial reefs promote more biodiversity in the long run than natural ones.”

Paik comes from South Korea, where artificial reefs are well established – just as they are in Japan. He has already installed an artificial reef around one kilometre off the coast of Sydney, which was sponsored by the Fisheries Board. The reef sits 38 metres underwater, weighs 40 tonnes and is 12 metres tall at its highest point.

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