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Seeded mussel lines filter seawater from beneath Te Wānanga

Innovative design partnership with Mana whenua shapes downtown Auckland

Published: 20 May 2021

Divers have attached 38 seeded mussel lines to the underside of Te Wānanga, the new public space which reaches out over the water in Quay Street.

With all 600 metres of rope, laden with mussels,  anchored in place, the kūtai / mussels will provide a truly living and organic connection between the city and the harbour.

While not destined for the table, each mature mussel will filter up to 150 to 200 litres of seawater a day taking in phytoplankton for nourishment as well as removing pollutants and acting as bio-indicators of aquatic health in the inner harbour.

The arrival of the mussels marks the beginning of the unveiling of many elements brought to six downtown projects through an innovative design partnership between Mana whenua, Auckland Council and Auckland Transport.

Read more about the partnership here [PDF].

The textured surfaces of Te Wānanga have been designed to encourage the attachment of seaweeds, barnacles and periwinkles and the ropes of green-lipped mussels installed today, signalling a collective intent to improve water quality and biodiversity.

The design partnership sees this innovative work raising public consciousness of natural solutions to created problems, placing these solutions into the most urbanised part of Tāmaki Makaurau and Aotearoa.

Dr Jarrod Walker (Nga Puhi), a marine scientist and technical advisor to Mana whenua has helped deliver the aspirations of Mana whenua as kaitiaki of Te Waitematā. Dr Walker also worked with Richelle Kahui-McConell who recently passed away, but he says her memory and work will not be forgotten.

He says: “Te Waitematā is a taonga tuku iho, and it should be treated as such. Unfortunately, this has not been the case historically. Today, Mana whenua wish to enhance the mauri of Te Waitematā and this project has provided an opportunity to develop practices and methods, grounded in Mātauranga Maori to move toward enhancing the health of the marine environment.

“Mana whenua’s name for this area is ‘Te Wānanga’ a place of learning. Mana whenua gifted the name to signify that this space will be an area where people can learn about Mana whenua’s deep connection with Te Waitematā and Tāmaki Makaurau, and for visitors to develop an appreciation for the harbour and to understand that we all need to care for the harbour and the marine environment.

“Mana whenua see the use of kūtai in this space as a step in the right direction to address both current and historic environmental issues impacting the mauri of Te Waitematā. This approach is just one of many programmes Mana whenua are implementing to regenerate the mauri of Te Waitematā,” says Dr Walker.

Marcus Cameron, a project scientist on the trial and a senior aquatic scientist with Tonkin+Taylor describes the remarkable water filtering capacity of mussels.  

“A single mature mussel can filter up to 150 to 200 litres of seawater a day taking in phytoplankton for nourishment as well as removing pollutants. They effectively act as bio-indicators of aquatic health, helping us monitor for any unwanted invasive species in the water,” he says.

The trial began in 2020. Around 100m of seeded mussel lines, weighing approximately 600kg were delivered from the Firth of Thames where North Island Mussels Limited have their operation.

They arrived at Kelly Tarlton’s last June for the start of the trial, where they were immersed in fresh water for 90 minutes as a biosecurity measure to kill any hitchhiking Mediterranean fan worm, invasive sea squirt and Asian kelp.

They then went into a tank of salt water overnight, so they were not stressed when relocated to the harbour. They range in size from 70-110mm and are about 18 months old – an age when mussels are often harvested for eating - but these mussels are not destined for the table.

The following day the seeded ropes were transported to the Maritime Museum where they were blessed by representatives of ngā Mana Whenua o Tāmaki Makaurau. 

Divers attached the kūtai ropes to two waka floats and three pile wraps and assisted in the hanging of the ropes from six pontoons in the Maritime Museum and Ferry Basin. The final batch of kūtai was attached to these structures in late June 2020. 

The 11-month trial was a success, and now 38 seeded mussel lines have made Te Wānanga their new home.

Programme Director Downtown Eric van Essen says: “This outcome captures the potential for Te Wānanga to encourage deeper understanding and appreciation of our different ecosystems and strengthen a living connection between land and sea in Auckland.”

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