Tim Harwood: Cawthron's seafood sheriff

Cawthron marine toxin chemist Tim Harwood.
MARION VAN DIJK

Cawthron marine toxin chemist Tim Harwood.

Continuing our summer science series, Naomi Arnold talks to Cawthron Institute marine toxin chemist Tim Harwood. 

As you tuck into freshly-harvested scallops and mussels this summer, spare a thought for Cawthron Institute marine toxin chemist Tim Harwood, who spends his working hours ensuring that delicious seafood isn't going to make you sick.

Harwood, an analytical chemist, has been at Cawthron since 2010, focused on toxin chemistry and seafood safety. The future of the multimillion-dollar New Zealand seafood export industry depends on having access to international markets and meeting their safety regulations. There is an internationally-accepted regulatory limit for each toxin class that applies across all shellfish, and part of what Harwood and Cawthron does is ensuring the industry has a voice overseas.

Harwood studied in Christchurch and then went overseas for a couple of years with his wife, an accountant, who is from Nelson. They were keen to return, but Harwood wasn't sure what science opportunities were available here. He was happy to find Cawthron.

"[It] not only did interesting research but also did stuff that aligned with my skills," he says. "I was really surprised. I thought I'd be working on an orchard picking fruit."

Being able to live and work in regional New Zealand is "really cool", he says.

"There's this migration towards the big cities but life in regional New Zealand is actually pretty darn good if you've got a job," he says.

Nelson is also a great place for him and his wife to raise their two young children, aged 3 and 4. A keen rugby player, Harwood refereed club rugby up until recently, and has also done some drug testing for Drugfree Sport NZ and the Cricket World Cup.

He also co-leads the Safe New Zealand Seafood research programme. Based at Cawthron, it's government-funded at $2.3m a year for seven years, with its main goals ensuring that New Zealand seafood is safe to eat and meets market requirements for food safety.

Working with Plant and Food Research, ESR and AgResearch, scientists and technologists perform research on various aspects of seafood safety, namely; harmful microalgae, bacteria and viruses. But the harmful algae research is Cawthron's specialty area. The team routinely analyses shellfish and seawater samples from all around New Zealand every week to determine whether or not there are toxins, or toxin producing microalgae, present.

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Microalgae are tiny plants that are like the ground litter of the sea, from which all other food webs grow. They can grow incredibly fast – sometimes in a matter of days – when light, water temperatures, and nutrients are right, but some species are harmful to marine life and to humans who eat seafood that is contaminated with toxins produced by microalgae.

There are two tools for the monitoring programme; one is looking at what's in the water and the other examines what toxins are present in the seafood itself, finding new ones and assessing whether or not they pose a risk.

"Shellfish are a high-risk product so it's really important there is a really solid management programme around it," he says.

"A lot of our work is on those toxins that are regulated, and establishing good, robust methods for them that are internationally accepted - but then there's also an element of looking out and horizon-scanning, seeing what's coming up, what could be a potential problem," he says.

"We're small, but well-regarded. We pioneered some of these testing methods that are adopted around the world for shellfish toxin testing so we feel like we've got some credibility and some mana in that space, and it's about trying to translate that into wins for the New Zealand seafood industry."

"New Zealand is in the unenviable position where we have all of the main toxin-producing algae in our coastal waters, so any time these things could become a problem," he says.

"[The aim] is to try and understand those processes, to be at the bottom of the cliff when they do happen, to see what's there and whether or not they are a real human health hazard."

The biggest threat to shellfish aquaculture is paralytic shellfish toxins, one you want to analyse correctly, Harwood says – because they can kill you.

Tasmania has recently had huge problems with this toxin class, with people getting sick and a forced shutdown of its shellfish harvest, impacting other species like lobster and abalone. 

Hobart is essentially on the same latitude as Nelson, he says, and there's no real reason to say that what's happening to them couldn't happen to us.

"I'd like to think our management tools are better developed than what they have so we wouldn't have as great an effect; but there's actually very little you can do to mitigate the algae in the water," he says. "So if they are there they will be there. All you can do is manage what's taken out of the sea and eaten."

Also top of the danger list is ciguatera fish poisoning, a "massive problem" in the South Pacific where reef fish get contaminated by algal toxins, affecting the food sources of local communities.

These algae may be introduced to our waters through warming coastal waters or ballast water; its prevalence is increasing, and it's already present in parts of Australia, including the northern NSW coastline. Cawthron has done a survey around Northland and has found a non-toxic microalgae species that is within the same genus as known toxin producers. However, the threat is always there.

But in some respects, there's nothing like a crisis to sharpen focus and push development and research forward. Since a major toxic shellfish event in 1993, the New Zealand shellfish industry and the Ministry for Primary Industries have conducted regular monitoring.

"We really didn't have a programme established at that stage to monitor them to know that there was a risk," he says. "We started to look down the microscope in the water to see what was present, and also started to test the shellfish flesh to see what toxins were there."

The looming spectre of climate change, with its impact on the temperature and acidity of sea water, is tipped to have an impact on marine aquaculture - industries like salmon farming are heavily affected by the temperature of the water. Last year was the world's warmest year on record, and there are no signs that it's slowing down.       

For shellfish, warmer waters might have their biggest impact on algae rather than the molluscs themselves. Mussels, scallops, and oysters are filter feeders and accumulate toxins. "It's a natural process," Harwood says. "It's really important to mention that."

Then once the bloom has been and gone, the toxins slowly depurate, or leach out, over the following weeks or months depending on which toxins are present. 

Nineteen ninety-three also happened to be an El Nino year, the periodic weather cycle that drives up global temperatures and disturbs weather patterns, causing both droughts and floods. It was also an El Nino year in 1998, when another big bloom happened. And it's El Nino again this year, predicted to be the strongest since 1998, sending sea temperatures higher and indeed expected to be among the three strongest ever recorded. What does that mean for our shellfish industry?

 "We're holding our breath wondering what's going to happen."  

 - Stuff

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