Invasive seaweed could take control

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There are concerns undaria will spread in Fiordland, risking black coral, and change the underwater seascape forever. PHOTO: DOC/SUPPLIED

IT has been 10 years since undaria (an invasive foreign seaweed) was found in Sunday Cove in Breaksea Sound; Fiordland Marine Guardians chairwoman Dr Rebecca McLeod said at that point there were just a few plants on a mooring line.

Undaria posed a threat to biodiversity and grew in different environments.

It was fast-growing and the size of it means it quickly out-competed native seaweed.

“You go from a really diverse seaweed assemblage to just undaria… it will impact the whole foodweb of the marine community.”

A joint-agency response was created and involved the guardians, the Department of Conservation, Biosecurity NZ and Environment Southland, and aimed to eradicate the pest.

“That was looking promising but what we didn’t realise was that while everyone was focused on getting rid of this incursion in Sunday Cove, there was another undaria incursion going gangbusters further up Breaksea Sound.”

With the vast amount of marine area in Fiordland, surveillance of the pest proved difficult and, by the time a second incursion was found in 2017, it had spread to a few kilometres in size.

Since then, the focus had moved to keeping it contained within that area.

That included communicating with boat owners and stressing the importance of cleaning vessels and gear. It also required all vessel operators entering the area to hold a “Fiordland Clean Vessel Pass” it travelling by vessel.

A “buffer zone” at the Breaksea Sound entrance was cleared once a month for a week at a time by divers who would rip the undaria from the seabed.

“It has been quite a massive effort, but it’s just becoming more and more apparent that that approach probably isn’t going to work,” Dr McLeod said.

A workshop with those involved in the response was held last month.

Environment Southland (ES) biosecurity and biodiversity operations manager Ali Meade said the goal was to discuss the future of the control programme following the loss of ES’s cruise ship funding and the discovery of Undaria pinnatifida on cray pots at Breaksea Island, which was outside the current containment zone.

“The agencies continue to be committed to eliminating undaria from Chalky Inlet.”

However, following in-depth discussions at the workshop, it was clear greater investment would be needed to contain and control the infestation of undaria in Breaksea Sound.

To help bridge the funding gap, ES recently put a proposal to central Government.

If successful and the control programme could be maintained, it would have positive outcomes not just for Fiordland (Te Moana o Atawhenua) Marine Area’s unique biodiversity but also Te Anau’s community, she said.

ES was committed to eliminating undaria from Chalky Inlet, which is not an exemption area, and were looking at alternative forms of funding for undaria control in Breaksea Sound which included forming partnerships with organisations and corporations with an interest in the restoration and environmental protection.

A $7.3 million application for undaria control and eradication in Fiordland through the Jobs for Nature programme was submitted.

It is a Ministry for the Environment (MFE) $1.3 billion programme, which is part of the Covid-19 recovery package.

An MFE spokeswoman said it was submitted as a response to a request sent out to all regional councils for investment-ready environmental projects which could create jobs to support New Zealand’s recovery from the economic impacts of Covid-19.

While it was not selected as one of the initial projects to be funded earlier this month, it may be funded through the Jobs for Nature programme.

Dr McLeod said they also worked on what their long-term objective was.

“What are we trying to achieve? Are we still trying to eradicate it, are we trying to contain it or are we happy for it to become part of the Fiordland ecosystem?”

It was determined the goal during the next 10 years was to limit the spread and mitigate the impact of undaria, and evaluate and report programme effectiveness, in order to maintain and improve the quality of Fiordland’s marine environment and fisheries.

The catch; it was dependent on receiving Government funding.

“We’re pretty much resigned to the fact it is impossible to eradicate it, however we know it will have serious effects on the marine ecosystem keeping it in restricted areas and low densities, we think we can mitigate the effects it will have.”

Advice was sought from scientists at the University of Otago, who suggested “adding another thread to the bow” by trying to reduce the amount of undaria in Breaksea Sound.

Dr McLeod likened undaria to thistle in that one plant producing all its dandelion heads could be blown away over an area, but a whole paddock of thistles meant the seeds were likely to spread beyond that paddock.

Therefore, more intensive clearing of the weed was needed throughout Breaksea Sound.

At present, divers were flown in by helicopter to the remote area and set up on a boat or barge for the week’s work.

“It’s a really expensive programme to maintain. So, what we’ve come up with is a plan where we can use the current charter vessel fleet, who are all really struggling for work at the moment, and use their vessels as a platform for accommodation for these divers,” she said.

Another idea proposed was to train people now needing work to freedive or snorkel to identify and remove the seaweed.

“With the Government Covid response package, we’re hoping that we can get support from central Government to fund this programme… this could be a really good way to employ locals.”

She said there was now simply not enough funding to “give it a really good push”.

“The guardians are concerned if this proposal doesn’t get funded, we are going to be in a position where we can’t be successful with the programme any more in Fiordland.”

If the programme failed, undaria would eventually spread through the fiords.

She said they did not believe New Zealanders would accept that unique environment “changing forever”.

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