Team pioneer artificial reefs for organisms
A product developed in Southland could help restore marine environments a pilot study has found.
The pilot used Lego-like building blocks to provide a habit for organisms in Bluff Harbour.
The study was conducted by Sea Nest directors Bryony and Waka Miller of Invercargill.
In the process of her work as a marine ecology consultant she had seen the decline in marine environments, Mrs Miller said.
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.
However, while there were overseas examples of artificial reefs none were suitable for the New Zealand environment as they contained heavy metals and other materials that would leach into the water over time.
The Millers worked with McGregor Concrete to develop 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.
"So very small scale, very low risk," Mrs Miller said.
The environment where the blocks were placed was in the middle of a big sand flat with a fast tidal current.
The nearest rocky reef was about 800m away.
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 unexpected results by diving in the area and an underwater camera.
It was commonly known sea creatures made homes of items that were thrown into the ocean "but even I was surprised".
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 eat 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.
