The famous gardens of purple, cauliflower-like corals that inhabit the waters off NSW's Hunter coast line could be lost within 10 years due to a combination of natural and human causes, scientists believe.
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Port Stephens is the only known location where Dendronephthya australis is found in large, habitat-forming clusters.
A 2019 Southern Cross University study found the clusters had declined by almost 70 per cent in just eight years.
Sediment mobilisation along with boat anchoring and moorings are the likely causes.
More recently, researchers were shocked to find high levels of run-off in the Karuah River catchment during the March 2021 floods had caused further destruction of the endangered coral.
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The coral species is likely to be extinct within 10 years if the current rate of decline continues.
"Although environmental conditions are still conducive to the presence of the corals within Port Stephens, this species has continued to decline. Modelling has shown there is a correlation between the loss of coral colonies over the past decade and sand movements within the estuary," PhD researcher Meryl Larkin, who is leading the joint NSW Department of Primary Industries and Southern Cross University study, said.
"While the models show that sand movement is likely to be a major contributing factor, many other factors can damage and kill colonies. Boat anchoring, moorings and fishing line have been observed impacting aggregations. There may also be other as-yet-undetermined factors at play, such as disease, pollution or other water quality issues contributing to their decline."
The Cauliflower Coral is one of the few temperate water soft corals found in NSW. The species is endemic to eastern Australia and it is currently only known to occur from Port Stephens to Jervis Bay.
Colonies of Cauliflower Coral not only provide shelter within their complex structure, but also support small crustacean (amphipod) communities, which are a key dietary component of many marine organisms.
Previous studies have shown that juveniles of the Australasian snapper Chrysophrys auratus as well as the Endangered White's seahorse Hippocampus whitei show strong preference for this soft coral habitat.
Specimens of D. australis have been recorded from Port Stephens since the 1970s.
"To watch it decline so rapidly has been very upsetting. Hopefully this study helps highlight the urgent need to implement measures to protect this species. We have started to investigate aquarium propagation followed by transplantation back to the natural environment to aid recovery. These early experiments have shown some promising results," Ms Larkin said.
Matthew Kelly
Matthew Kelly has worked as a journalist for more than 25 years. He has been working as a general reporter at the Newcastle Herald since 2018. In recent years he has reported on subjects including environment, energy, water security, manufacturing and higher education. He has previously covered issues including the health and environmental impacts of uncovered coal wagons in the Hunter Valley, the pollution of legacy of former industrial sites and freedom of information issues.
Matthew Kelly has worked as a journalist for more than 25 years. He has been working as a general reporter at the Newcastle Herald since 2018. In recent years he has reported on subjects including environment, energy, water security, manufacturing and higher education. He has previously covered issues including the health and environmental impacts of uncovered coal wagons in the Hunter Valley, the pollution of legacy of former industrial sites and freedom of information issues.
