Scientists hoping to boost marine life and water quality in the Hauraki Gulf are buoyed by the instant success of a trial to re-establish mussel beds on the seafloor.

Seven tonnes of live greenlipped mussels dumped in separate plots off eastern Waiheke last November have survived and are functioning as a reef, attracting fish and marine organisms, says marine scientist Dr Shane Kelly.

As these before and after pictures show, the mussels have matted together over a once barren seafloor and been colonised by a range of marine species.

The Revive our Gulf project aims to restore naturally-replenishing mussel beds which once carpeted vast swathes of the gulf, providing valuable nurseries for juvenile fish and improving water clarity with their filtering effect. The reefs were wiped out by dredging between 1910 and 1960 and replaced by sediment.

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Until the trial, scientists were grappling with how to re-establish the beds. The surplus mussels were donated by North Island Mussels Ltd and seven "living room" size plots established in a sheltered bay off the island. "After some initial mortality and some expected predation by starfish and snapper, the remainder have survived really well," said Dr Kelly, the project's research director.

Working with Auckland University students, the volunteer group plans to keep a close eye on the plots and restock them until they become self-sustaining. It aims to expand the project with community support "bay by bay".