Entire ecosystems off the NSW coast are at significant risk following massive declines of soft coral habitats, according to a team of researchers at the University of Newcastle.
Between the Central Coast and Port Stephens, the species Dendronephthya australis, cauliflower coral, has declined by up to 90 per cent and has become the first soft coral in Australian history to be listed as threatened.
Beginning as a university honours project by Hannah Finlay-Jones, the study looks into the role of the endangered cauliflower coral as a habitat for fishes and invertebrates and whether species used the soft coral as a food source.
While previous work found that large fish didn’t directly feed on these corals, Jones and her team found the small invertebrates, tiny organisms, and crustaceans relied on the corals as part of their diet.
These animals are an essential food source for fish further up in the food web, signalling that losing these soft coral habitats could have broad, adverse effects on coastal waterways.
Supervising the study was postdoctoral researcher and marine ecologist Dr Vincent Raoult, who said there had been a decline of these soft coral habitats in NSW for more than a decade.
“It’s quite alarming that these animals and coral habitats are starting to disappear without us even knowing what their roles are in our ecosystems and what negative impacts those declines could have,” Dr Raoult said.
“These soft corals align with the hard corals you would find in the Great Barrier Reef. They have these complex structures that provide lots of areas for animals to live and thrive in and provide a food source.
“When we delved deeper and looked at the tiny organisms that lived on these corals, we found that the vast majority of them fed almost exclusively on the soft corals.”
Dr Raoult also said the White’s Seahorse was a threatened species that lived on and ate the organisms of these soft corals, which was an integral key to the seahorse’s survival.
“These soft corals are an important factor in our coastal ecosystems and are now officially listed as threatened,” he said.
The soft coral decline is attributed to human interference such as boat anchoring, poorly installed boat moorings and entanglement by fishing line.
“The biggest threat is sandbank movement because these animals are not very mobile, which means they get smothered by sand fairly easily,” Dr Raoult said.
“So, big movements of sand caused by openings and closings of estuaries, for example, can smother the corals and cause a lot of deaths.”
The research paper concludes by calling for remediation and management actions to ensure Dendronephthya australis does not become extinct in the region.
Dr Raoult said some actions being trialled included mapping the corals in Brisbane Water to help get an idea of where the corals occur.
This mapping opens up an opportunity for monitoring and protection, limiting boat anchoring, mooring and dredging in certain areas.
“Another action being taken based out of Port Stephens is developing ways to grow these corals in aquarium conditions so they can be released and replanted in the environments they have been lost in,” Dr Raoult said.
He said action could also take place at a grassroots level, asking the community to be careful and aware of these precious ecosystems.
“If you are doing any boating, please have a look at where you’re dropping your anchor; these soft corals are really noticeable because they look like big cauliflowers on the ocean floor,” he said.
“You can see them clearly through the water, so try to avoid putting anchors or fishing lines in those areas.
“These habitats occur quite literally at an arm’s length in some shallow parts of Brisbane Water, right next to the shore, so being aware that they are there is so important.
“The more people that know of these amazing habitats will broaden the overall awareness of the community, showing everyone why it’s so important that we do everything we can to protect them.”
Hayley McMahon