Sea Nest director Bryony Miller spoke at the New Zealand Marine Sciences Society conference in Invercargill on Thursday about the study to rewild a small section of Bluff Harbour.
The Invercargill-based ecologist said in the process of her work as a marine ecology consultant she had seen a decline in marine environments.
While harbours and marinas were well-utilised, it was rare for people to consider how to enhance or improve the environment, she said.
This understanding set her on the path to considering how to do this.
The idea was born to make modules similar to building blocks which could act as artificial reefs to provide a home for organisms.
She and husband Waka, in conjunction with McGregor Concrete, have produced the modules, which will last 100 years in the water without polluting the environment.
The study, which began in May 2024, involved placing six modules in water about 6m deep near a consented marine farm.
‘‘Very small scale, very low risk,’’ Mrs Miller said.
The nearest rocky reef was about 800m from the shore.
The environment where the blocks were placed was in the middle of a big sand flat with a fast tidal current.
Sea lettuce, red drift algae, turret shells and several spotty fish were some of the few organisms living in the area, but there was no seagrass or shellfish beds.
Strings seeded with kelp were tied to the modules.
The couple observed the modules’ effects by diving in the area and using an underwater camera.
The results were unexpected.
After two weeks, four new taxa or groups of organisms had moved into the modules.
‘‘After six weeks, it increased up to 13 taxa, and after five months we saw a hit at about 23 taxa.
‘‘So, it was quite a rapid migration of species.’’
Once algae were established, animals that ate it moved in and then came predators, including two conger eels.
‘‘Spotties used it like an apartment block, which was really cool to see.’’
After the success of the pilot the couple have received South Port consent permission to place the modules in two other parts of the harbour.
