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perception is that cities, and their associated ecological impacts end at the
waterline. However, coastal cities such as Sydney are also highly modified
underwater. Below the waterline in Sydney Harbour there is a dense network of
coastal infrastructure, the sediments hold a legacy of chemical contamination
and shipping activities contribute further stress through antifouling biocides
and invasive species.
Healthy estuaries have some natural mechanisms to recover
from such stress and much of this is driven by the small invertebrate creatures
living on rocky reefs and burrowing through sediments. However, in Sydney
Harbour and other urbanised estuaries we have lost many of these important
critters, and so have lost their natural capacity for recovery.
Oyster reefs in
particular have historically played crucial roles in maintaining healthy
estuaries by filtering water, providing habitat for fish and invertebrates and
protecting shoreline ecosystems. Centuries ago, estuaries on the south east
coast of Australia were packed with intertidal and subtidal oyster reefs,
hectares wide. Nowadays, subtidal oyster reefs are mostly absent due to human factors,
including the harvesting of shells and live oysters since the 18th century. One
of those remnant reefs is located in Towra Point, Botany Bay. The scale of the
reef is impressive, but also a sad reminder of what we have lost from other
The Sydney Harbour Research Program at SIMS has started a project to restore oyster reefs around Sydney, and
to do so at meaningful scales that will rival reefs like the one at Towra Point.
Through this project, we focus not only on increasing oyster numbers, but on
quantifying the positive feedbacks such reefs can create, including
rehabilitation of degraded sediments, improvements in water quality and
shoreline protection. We will work, not only for the recovery and resilience of
urban estuaries to global change, but also to enhance the socio-economic
benefits to the communities that rely on the resources coastal ecosystems
This research is a collaboration between SIMS and the University of Sydney and is generously supported by the Maple-Brown Family Foundation.