In its natural environment, seaweed plays a major role in marine ecosystems. Not only does the plant provide nutrients and energy for organisms up the food chain, but these plants also provide shelter and habitat for many different species. So when 70 kilometers of seaweed vanished from the Australian Coast in the 1970s and 1980s due to high levels of sewage, we would expect to see some dramatic environmental problems. But thanks to recent recovery efforts, a habitat-forming species known as crayweed is making a successful comeback in Sydney's coastal waters.

 

Despite improved water quality around Sydney after the introduction of better infrastructure in the 1990s, which pumped sewage into the deeper ocean, the 70 km gap of depleted 'underwater forest' — between Palm Beach and Cronulla - has never been able to recover naturally.

 

In an effort to restore the seaweed, a team of researchers from the University of New South Wales (UNSW), the Sydney Institute of Marine Science and the NSW Department of Primary Industries has transplanted fertile specimens of the missing crayweed (Phyllospora comosa) onto two barren reef sites where it once grew abundantly.

 

"Seaweeds are the 'trees' of the oceans, providing habitat structure, food and shelter for other marine organisms, such as crayfish and abalone," says lead author, Dr Alexandra Campbell, from the UNSW Centre for Marine Bio-Innovation.

 

"The transplanted crayweed not only survived similarly to those in natural populations, but they also successfully reproduced. This creates the potential for a self-sustaining population at a place where this species has been missing for decades," she says.

 

The researchers say their results could provide valuable insights for restoring similar macroalgae marine ecosystems in Australia and globally, but further research is needed to understand the complex processes that affect recruitment and survival.