'Lab in a can' tests toxic algae as Marlborough Sounds set for another bloom

Thursday, 2 May 2019

New technology is being used in the battle against the toxic algae that has previously caused mass mussel farm closures in the Marlborough Sounds.

The 'imaging flow cytobot' is an underwater camera that uses artificial intelligence to identify dangerous strands of phytoplankton in real time. 

Dubbed a 'lab in a can', the instrument takes water samples every 20 minutes and photographs the contents. It is being used for the first time in New Zealand. 

Californian scientist Dr Raphael Kudela brought the instrument over from the United States and has been working alongside scientists at the Cawthron Institute for the past nine months. 

**READ MORE:

* Algal blooms in Marlborough Sounds could be an annual issue for mussel farmers

* Marlborough Sounds mussels get fat on toxic algae as harvest pushed back

* Underwater seaweed forests tipped as next big thing in climate change fight**

'It's kind of like using a normal microscope, but you can take this instrument out into the field or bring it on a boat with you and it just does everything by itself,' Kudela said.

'We can look at what kind of phytoplankton are there, but what we're particularly interested in, is looking for the harmful species which produce toxins.'

Phytoplankton are a microscopic marine algae which form the base of the food chain. 

'We can look at the health of the ecosystem by looking at what sort of phytoplankton are in the water,' Kudela said.  

'Mostly they're good, it's the things that are feeding the zooplankton and then the fish, and so it supports the aquaculture and salmon industry. But a fraction of that phytoplankton can be dangerous.'

Last year, more than 100 mussel farms in the Kenepuru Sound and inner Pelorus Sound were closed after the toxic algal bloom Alexandrium catenella was discovered in the shellfish. 

The closures were believed to be the largest number since 1993, and raised concerns among industry that it could become an annual issue. 

'It seems like it's probably going to happen again this year. So far the cells are definitely there at a pretty high concentration, but they're down in a sub-surface layer,' Kudela said. 

'We're waiting to see if they are going to come to the surface and form a big bloom or not.'

Marlborough's climate was like California's, which also struggled with a similar strand of algae bloom, Kudela said. 

'Not exactly the same species, but very similar problems.'

Ministry for Primary Industries issued a public health warning against collecting shellfish in the Pelorus Sound, excluding the upper Kenepuru Sound in March.  

'It seems like a problem that's not going away and it is certainly here again this year.'

The instrument allowed the team to get higher quantities of samples than traditional methods, he said. 

'The first thing you need to know is that the cells are actually there and you need to pay attention. 

'If the cells are growing and accumulating, say in the mussels, there's not much you can do, other than not eat the mussels. Eventually they'll get rid of the toxin on their own.

'For the growers, they just need to know how long the bloom is going to last and where the bloom is, so they can decide if it's going to be a short-term closure or a long-term closure.'

They were still working on the 'big question', could they get rid of the algae in the first place?

'Probably not, they are part of a natural community,' he said. 'But we do know that there are things that make it worse.'

In California, they had good evidence that 'nutrient pollution' like nitrogen and phosphorus loading, caused by runoff, could lead to more problems. 

'We have been implementing rules that try to limit nutrient runoff into the coastal waters.'

Algae were basically plants, and needed sunlight and fertiliser, he said. 

'The more fertiliser you put in the water, the more likely you are to get algae growing of all kinds, including the toxic ones.'