The invasion of our waterways

We are used to airborne invasion. Deadly mosquitoes, painted apple moths, varroa bee mites, Asian gypsy moths - they've come in waves and our authorities have (eventually) got them under control.

We have strategies to repel ground assaults - MAF mobilised in impressive fashion when a Foot and Mouth outbreak was threatened on Waiheke Island in May.

But when it comes to submerged threats, be afraid, be very afraid. Biosecurity NZ stands accused of refusing to get its feet wet to tackle a gooey, slimy invader threatening to ruin our pristine highland rivers and streams and their lucrative trout fisheries.

Our leading biosecurity agency is under siege for its response not only to didymosphenia geminata - the river-threatening algae politely known as didymo - but to undaria, an invasive seaweed, and the clubbed tunicate, a sea squirt which could smother much of our marine-farming industry.

They are respectively labelled rock snot, the gorse of the sea, and the marine equivalent of painted apple moth. Visiting scientists uncovered two of the three by chance.

A Japanese researcher on holiday spotted undaria in the Viaduct Harbour and Westhaven in September last year. The sea squirt was found in the same location in August by a visiting British marine biologist. The Lyttelton specimen was in a sample taken late last year but only recently analysed, which raises another issue.

While these invaders have the potential to multiply and spread rapidly, our fledgling biosecurity agency is accused of treading water. Formed last year to plan and co-ordinate our defence against unwanted aliens, the MAF offshoot faces questions about its rapid-response capability, resourcing and ability to communicate and work with other agencies.

There is concern about whether enough is being done to prevent unwelcome guests arriving in the first place, through a tougher line at airports and more robust maritime laws.

"Yes, we have come a long way with the biosecurity strategy and Biosecurity NZ being set up," says Forest and Bird Canterbury field officer Eugenie Sage. "But the Government seems unwilling to get serious about funding and allow more focus on control techniques and research."

New marine pests don't have the same leverage in Wellington as terrestrial threats to our agriculture and horticulture, she says. "A lot of money was thrown at painted apple moth. But with marine and freshwater ecosystems there's not the same hard-headed and co-ordinated response."

After Biosecurity NZ announced surveys last week to reveal the extent of sea squirt infestation in Auckland and Lyttelton harbours, the marine-farming industry gritted its teeth.

Aquaculture Council chairman Callum McCallum welcomed the surveys but asked why they had taken more than a month to organise.

The clubbed tunicate's presence in the Waitemata has alarmed Hauraki Gulf and Coromandel mussel farmers. McCallum says all recreational users should be worried - adults are prolific breeders and concentrations can reach 1500 a square metre.

McCallum, a Clevedon oyster farmer, and others in the sector are puzzled by the agency's insistence on following protocols. He says eradication options are already known and the industry can't afford to wait for the survey. "Immediate steps must be taken now to eradicate the known breeding colonies."

Fears about the ease with which it could spread to the Marlborough Sounds were confirmed this week when one was found on a boat which had sailed from Auckland to Picton. The vessel had spent time in Lyttelton before spending some months berthed in the Viaduct Harbour. Luckily, the organism was too young to breed.

But the shellfish industry's unease is nothing compared with the flak over didymo coming from the South Island and the Taupo-Turangi trout fisheries.

In mid-September, after Biosecurity allowed whitebaiters (with restricted-movement permits) to use the two affected Southland rivers, the Waiau and its tributary the Mararoa, its didymo control programme was called a joke by Environment Southland councillor Ted Loose.

"I've got no faith in their ability," he told the Southland Times. "If this spreads everywhere, and it very well could, there'll be hell to pay."

A week later, there was. Didymo appeared in the Upper Clutha and Hawea rivers in Otago and the Buller River on the West Coast. Its presence is also suspected in the Waitaki in South Canterbury. Environmental watchdogs rounded on the agency for failing to do more to confine the algae to the Waiau and Mararoa.

"All we see them doing is monitoring, doing studies and sending out notices," Otago Regional Council chairman Stephen Cairns told the Otago Daily Times. "The council is not prepared to accept that the horse has bolted ... We are going to step into what we have seen as a void and take a leadership role."

There was incredulity when the agency allowed this weekend's World Jetboat Marathon to go ahead, raising the prospect of boats spreading the algae from river to river.

Biosecurity believed the risks could be averted by cleaning boats before they moved. After an outcry, organisers excluded rivers known to be contaminated.

Didymo's threat to our waterways is the stuff of Dr Who. Its microscopic cells can be transferred between streams in a drop of water and remain invisible until they bloom.

The thick brown or white-layered blooms coat riverbeds in dense, gooey mats that suffocate desirable life by excluding other algae that support the insect life that fish eat.

Our clean, green image could suddenly appear grey and polluted. Floating or dried mats are mistaken for toilet paper, raising fears of sewage contamination.

Warmer areas


It is suspected to be a cool-water, high-country threat, but we don't know for sure. Its spread into warmer areas in the United States means it may become established in lowland rivers in the North Island.

The volcanic plateau rivers are thought to be the most suitable North Island environment for didymo. Around Taupo and Turangi, centre for nearly 40 per cent of the country's trout fishing, people are anxious about the potential economic and environmental effects.

In the western United States, some fisheries declined by 90 per cent in 2003 and last year. There are reports of it clogging the intake screens of hydro power stations but it is far from a given that didymo will deliver on its potential here.

That's the problem, says Niwa freshwater scientist Cathy Kilroy, who found the algae in the Waiau last year and has led research into the likely risks.

"We just don't know enough about its lifecycle and how it will behave in New Zealand conditions."

While there have been rampant, thick blooms in Europe and North America, they vary and so does their impact on aquatic life.

"We really don't have much of a handle on it yet," she says. "All we know is that it does grow in much greater quantities than any other algae that we've seen and it seems to be much more persistent.

"Once it's there, it's liable to be there for a while."

Biosecurity's response to Niwa's research was containment. It reasoned there was no practical way to eradicate didymo, while closing the rivers offered no guarantee that the organism would not be spread by birds and other animals.

It was worried about the "significant cost" of closure to the tourism and fishing sectors and recreational users. Instead, it launched an awareness programme about the movement and treatment of equipment.

Freshwater scientist Mike Joy, of Massey University, says more should have been done to quarantine the rivers and educate travellers. There was the option of "nuking" (chemically treating) the river. "It would kill everything but you can always get it back."

Not all scientists agree. "If there is one certainty in the didymo debate, it is that there are no realistic prospects for eradication either currently available or even likely in the near term," says Otago University senior ecology lecturer Gerry Closs.

At least some of the criticism levelled at Biosecurity NZ has been misinformed. Senior adviser Amelia Pascoe says it is now thought didymo has been in the lower Waiau and Mararoa for up to four years "so just because we are starting to find it in some of these other rivers now doesn't actually mean that it has only spread in the last few months".

And Niwa scientists felt unable to suggest any eradication options because they could find "no published examples of attempts to control or eliminate blooms".

So our marine biosecurity strategy might just pass muster were it not for the fuss about undaria in Auckland. Listed among the world's 100 worst invasive species, the Asian seaweed can rapidly displace native kelps, restrict the lifecycle of shellfish, such as paua, and threaten aquaculture.

Found in Westhaven in September last year, it has spread along the port area, including Viaduct Harbour, and been found at Kawau Island.

Undaria was discovered in Wellington Harbour in 1987 but northern waters were thought too warm for it. Its discovery at Stewart Island in 1997 prompted a successful Department of Conservation control programme which reduced the number of plants removed each year from around 20,000 in 1997 to 70 plants last year.

But funding ran out about the same time that Biosecurity NZ opted out of further undaria control because it could not be eradicated nationally. Last December, Biosecurity NZ told the Auckland Regional Council undaria was now a regional concern.

The ARC says the government agency has the expertise, experience and legal powers to manage undaria and is the only organisation able to prevent its spread between regions and within territorial waters.

Estimates of the cost of a clean-up operation range from $1.62 million to $2.67 million, which the ARC says exceeds limits placed on regional councils under the Biosecurity Act.

Meetings with the agency have failed to persuade a rethink. While the standoff continues, the risk increases that undaria will get out of control, say ARC officials.

Peter Thomson, Biosecurity NZ's post-clearance director, says New Zealand and Australia lead the world in tackling marine biosecurity but face a steep learning curve. Border controls against ballast water and hull fouling are new concepts internationally and tracking of underwater hitchhikers is difficult.

"It's a bit late, but every one of these incidents helps to strengthen our borders for next time. "We have demonstrated [on land] that we have the capability to respond rapidly.

"What is difficult for the lay person to understand is that we have to base our actions on the best [scientific] information available. When we get something completely off everybody's radar, like didymo, we are really starting from scratch."

Undaria was long-established and there would always be tough choices on funding priorities, "just like the health sector".

As for the squirt, Niwa staff surveying in Lyttelton and the Waitemata are licensed to kill.