University of Waikato PhD student Megan Ranapia. Photo / supplied
University of Waikato PhD student Megan Ranapia. Photo / supplied
Efforts to stop culturally and ecologically important Bay of Plenty mussel reefs from being smothered by sea stars have been discussed at a science conference in Tauranga this week.
The University of Waikato's Tauranga campus is hosting 360 scientists for the New Zealand Marine Sciences Society Conference.
Megan Ranapia, aPhD student in marine ecology at the university, said sea stars were threatening mussel populations in Ōhiwa Harbour, near Whakatāne.
"The issue in Ōhiwa is the numbers are so high with sea stars that they've basically gone along and decimated the mussel beds.
"The way they consume is they overt their stomachs out and smother the shellfish."
In her presentation to the conference, Ranapia showed an image from the eastern boundary in Ōhiwa Harbour of about 100,000 sea stars on a two-hectare pipi bed - about 50 sea stars per 10 square metres.
Ranapia said her PhD research was about co-developing mātauranga Māori (indigenous knowledge) and science to inform sea star management in the harbour.
This meant collectively working with iwi partners on their issues, needs and aspirations for the harbour, she said.
"There are many coastal iwi, hapū [and] whānau who are wanting to integrate their mātauranga into marine research management and policies."
She said Ōhiwa was "a really good example" because there were four affiliated iwi with the harbour and it was seen as important for traditional food gathering.
"There's been a significant decline in our traditional kaimoana and in particular the mussels."
It is the first time in 40 years the conference has been hosted in Tauranga. Photo / Megan Wilson
The harbour was managed by Ōhiwa Harbour Implementation Forum and rōpū kairangahau (researchers). Co-development meant working with them to identify why there were so many sea stars and how to manage them, Ranapia said.
Ranapia told the Bay of Plenty Times mussels were "eco-system engineers" that provided habitats, nutrients and food for other marine species.
"Mussels are culturally and ecologically significant ... particularly in Ōhiwa Harbour because of their hard structure ... they replace what rocks provide for other animals to settle on and shelter in."
Al Alder, a PhD candidate in marine science at the University of Auckland, addressed in his presentation "some of the awesome work done" in Ōhiwa for mussel reef restoration.
"They're passively collecting mussels at these restoration stations, creating new beds around them and replenishing the existing beds that are there."
He said in some cases, mussel reef restoration involved moving mussels from A to B.
"It's taking mussels from aquaculture long lines, barging them out to a site and then spreading them across the seafloor where, over time, they're going to form into these mussel reefs namely over soft sediment.
"This is a small part of restoring this environment … [it] involves the kind of stuff we've been seeing in Ōhiwa Harbour, active translocations but also conserving the remaining mussel beds we have."
PhD student at the University of Auckland Al Alder. Photo / Megan Wilson
Sophie Roberts, a PhD candidate in marine science at the University of Auckland, spoke about her mussel restoration project monitoring two sites in northeast Auckland.
"We want to successfully restore an eco-system," she said.
"[Mussels] ... provide a range of ecosystem services and functions that we can benefit from ... They provide habitats, stabilised sediment and improve water quality."
Conference organiser and University of Waikato chair in coastal sciences Professor Chris Battershill said the issues and potential presented by New Zealand's marine environment were enormous.
"We're working against a backdrop of climate change, and we need to ramp up conservation and restoration in our marine environment."
In a media release the university said research from the Government's sustainable seas science challenge estimated New Zealand's marine economy could contribute up to 3 per cent of New Zealand's GDP in the future.
The Government had also set a target to grow New Zealand's aquaculture to a $3 billion industry by 2035.
The conference, which is being held in Tauranga for the first time in 40 years, started on Monday and will close tomorrow.
