In the dark of the deep ocean floor, where sunlight seldom reaches, sponge gardens flourish in spectacular colours and formations.

These plant-like organisms attached to rocky shelves are ancient animals that have been around since the dinosaurs.

Like an underwater rainforest, the colonies provide food and shelter for marine life and are essential for ocean health.

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And now the humble sponge is central to a novel research project aimed at shoring up the ocean food web, as human-induced pressures like climate change and ocean-based industrialisation mount.

Sinking 120 tonnes of rubble

Marine biologist Chris Gillies and his Gippsland-based team from Offshore Biotechnologies will drop 120 tonnes of rubble onto the sea floor in the Apollo Marine Park, off the coast of south-west Victoria, as a trial to grow new sponge communities.

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“The rock, with all the grooves, will attract plankton, baby sponges and baby corals, [and] the hard surface creates the reef and colonises the sea bed,” Dr Gillies said.

The rubble is also carrying precious cargo — baby sponges or “nurseries” propagated from adult sponges that were collected, divided into small bits and grown in a hatchery.

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The method has gained interest and $2.21 million financial backing from Parks Australia, which manages Australian marine parks.

The authority is scoping the method for its application to make marine parks more resilient ahead of predicted climate change-induced marine heatwave events.

Commercial partners have matched Parks Australia’s funding.

An energy company proposing gas extraction development, an American not-for-profit and the fishing industry are partners.

Ocean ‘forests’

Dr Gillies said sponge gardens were rich in biodiversity and played an essential role in the aquatic food chain by filtering huge volumes of seawater and providing plenty of nooks and crannies for habitat to thrive.

He said he believed new “sponge nurseries” could be used to revitalise fisheries and repair damage to the sea floor from ocean-based construction, including for oil and gas extraction and offshore wind farms.

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“The offshore space is developing. We already have offshore oil and gas — it’s been around for a long time — we have aquaculture, that’s starting to move into these areas and and that’s all providing pressure on these seabed ecosystems,” Dr Gillies said.

“Of course, climate change is changing the temperature of the water and the chemistry of the water as well.”

Dr Gillies said losing sponges was like chopping down a forest — removing an integral section of the food web.

“On land, we’ve got lots of great methods to restore a forest or a grassland, but underwater, we don’t,” he said.

“That hasn’t happened in the past, which makes this project novel.”

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Deakin University marine biologists Mary Young and Dan Ierodiaconou will monitor the project.

“Reef restoration is commonplace in shallow water systems, but it’s rare to find examples like this in deeper [waters],” Dr Ierodiaconou said.

“By using underwater drones to collect images, we will be able to track the changes taking place.”

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Dr Ierodiaconou said his team had been monitoring reef systems in Bass Strait for more than two decades.

“The research will go some way in informing future nature-based design when designing future marine infrastructure or decommissioning assets that reach end of life, such as those we are seeing in Bass Strait related to oil and gas,” he said.

Getting ahead of the heat

Parks Australia’s Barbara Musso said the research presented an innovative conservation opportunity for the authority.

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“Climate change is expected to increasingly drive changes in sea floor ecosystems … particularly through marine heatwave events,” Ms Musso said.

“As marine heatwaves become more frequent and intense, Parks Australia needs to understand and explore management options in response to these events.”