Wednesday, August 10, 2022
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Health check for the harbour

It’s important work on a number of levels.

More than 50 per cent of the Sydney harbour foreshore features sandstone or concrete sea walls. Unlike rocky foreshores, these small, flat, vertical surface areas are not conducive to intertidal organisms or mobile species like limpets, sponges and anemones; crabs, snails and starfish. As a result, biodiversity is reduced and the overall health of the waterway tends to suffer.

Moreover, the demand for coastal defence will increase, in Australia and the rest of the world, as sea levels rise due to global warming.

Ms Morris describes her work in terms of “putting biodiversity back into sea walls”.

The Centre for Research on the Ecological Impacts of Coastal Cities has focused, over a number of years, on introducing artificial rock pools to sea walls throughout Sydney harbour to increase biodiversity. Under the supervision of Associate Professor Ross Coleman and in collaboration with designer Anthony Luck of ECS Services, Ms Morris has installed 20 concrete pots along the sea wall at Blackwattle Bay. At low tide the pots, produced by Antique Stone and measuring approximately 300mm in diameter, mimic rock pools, attracting various marine species.

“We installed the first 10 pots late last year, and with the help of tiny cameras we have been able to measure the visitation rates of fish and crabs, as well as algae growth and so on,” Ms Morris explained. “We’ll also note the visitation rates of predators, which are crucial to biodiversity.” The wide-angle cameras are designed to capture time-lapse images, which, over the next two years or so, will provide detailed information on the health of the bay and harbour.

“We’ll see what colonises naturally,” said Ms Morris, who collects data from each pot every two weeks. She will also be able to compare her findings with similar trials at Cremorne Point and Careening Cove where a 118 per-cent increase in mobile species activity has been recorded over a seven-month period.

Ms Morris summarised: “Research into engineering sea walls is needed to conserve the species that lose their natural homes; without it we will lose many of the species that cannot live on sea walls as they stand currently. The pots are a relatively inexpensive way for councils and other businesses or organisations to sustain the intertidal biodiversity of cities where sea walls are inevitably going to replace vast areas of intertidal platforms. The aim is to produce documents on the long-term durability and biodiversity benefits of these types of sea-wall enhancements. This information will then be used by councils, initially throughout Sydney harbour, to make their sea walls more environmentally friendly. This research could be applied to the management of sea walls worldwide.”

Ms Morris has found members of the public quite curious about her work. “Some people stand and watch what I’m doing [at the pots],” she said. “They seem to be very interested and to care about the foreshore.”

The City of Sydney, through its Environmental Grants Program, has been strongly supportive of the research, providing the funds that enabled the installation of the cameras. The Council has also helped to foster public awareness. “Sophie Golding, the City’s urban ecologist, has been a pleasure to work with,” Ms Morris said.

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