Our Changing World: Tauranga’s living sea wall

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Coastal critters have new habitat options along the Tauranga waterfront, thanks to the installation of 100 'sea pods' or 'living boulders' in May 2024.

Weighing up to 1.2 tonnes each, the sea pods are indented with holes and crevices that mimic rocky tide pools, providing space for tiny organisms from shrimp to anemones to find a home.

One year on, researchers are monitoring the manmade rockpools to find out what species have moved in.

Reclaiming the waterfront real estate

Constructed as part of Tauranga City Council's long-term strategy to redevelop the harbour, the sea pods aim to bring back biodiversity often lost in urban coastal areas.

David Culliford, marine scientist at Toi Ohomai Institute of Technology, says urban modification over time has impacted marine life.

"There's a tapas bar over there and if you look next to that there's some old piles which were part of the original harbour structure, and they're probably about 150 metres back from where we are right now," he says.

Tauranga Harbour, like many other city harbours, sits on reclaimed land. Rockpools and other coastal microhabitats have been covered up to make way for manmade constructions like sea walls or wharves.

A 'living sea wall' provides ideal real estate for many shoreline-dwelling species, encouraging biodiversity to recolonise the urban waterfront.

Sydney's pioneering sea walls

The idea of a living sea wall was developed in Sydney, Australia, through 30 years of research. The approach combines engineering and ecological concepts to create designs for pilings, panels and other modules that meet both human construction requirements, and wildlife habitat needs.

Specially designed panels were installed on a North Sydney sea wall in 2018. Monitoring the biodiversity over time, researchers found a 36 percent increase in the number of different species living on the sea wall, compared to a sea wall with no modifications.

"So we're re-introducing habitat, we're re-introducing habitat variety and so we can increase biodiveristy," says Dr Aria Lee, marine ecologist at Living Seawalls, a programme of the Sydney Institute of Marine Science.

There are now 20 Living Seawall installations across Sydney Harbour, and around 1000 around the world in the UK, USA, Europe, Asia, Peru and, of course, Tauranga.

Tauranga's 'sea pods' were designed by Living Seawalls in Sydney. But rather than ship tonnes of concrete across the ocean, silicone moulds were cast and sent to New Zealand for local manufacturing with concrete and recycled materials.

One year of 'sea pod' science

Ongoing monitoring is tracking the changing biodiversity as the seasons, weather and tides shift.

Tiff Cooper and Taylor Rabbitt, marine science students from Toi Ohomai Institute of Technology, conduct surveys to record the abundance of different organisms and measure algae cover and growth.

Together with David and collaborators from the University of Waikato, they have documented branching algae, colourful sea slugs, and dancing flatworms, as well as "heaps of shrimp", says David. "They seem to be like little shrimp hotels, we find loads of them in here."

They even found possible signs of the harbour's unique sneezing sponge colonising the sea pods.

David plans to install GoPro cameras to see what marine organisms take up refuge in the sea pods when they're covered with water at high tide.

Plus, the eye-catching structures often elicit questions from curious members of the public.

"We always get lots of enthusiasm while we're down here, it's cool," says David.

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