Coastal and Freshwater news

New Zealand’s freshwater algae is under the spotlight for a Marsden-funded research programme
8 August 2016

What lurks beneath…revealing the secrets of freshwater algae

An international team of scientists researching toxic algal blooms in lakes have provided new insights into why these microscopic organisms produce toxins.

The research team, co-led by Professor David Hamilton from the University of Waikato and Dr Susie Wood from Cawthron Institute, have been investigating what triggers toxin production in planktonic cyanobacteria (also known as blue-green algae) as part of a three-year Marsden Fund project. Also working on the project is post-doctoral researcher Dr Jonathan Puddick from Cawthron Institute, and Professor Dan Dietrich of University of Konstanz, Germany. 

“Thanks to this research, we’ve gained new knowledge on the ecological role of toxin production. It appears one of the reasons they produce toxins is as a coping mechanism in response to extreme shifts in their environment created when blooms form,” Dr Wood says.

“Unlike many organisms which produce toxins to protect themselves against predation, we believe that toxin production in cyanobacteria protects the cells from adverse conditions.”

A cyanobacterial bloom at Lake Rotorua, Kaikoura

In collaboration with Professor Ian Hawes from the University of Canterbury, the team used micro-profiling techniques to show how harsh the conditions inside a cyanobacterial bloom are.

“At certain times during the day pH reaches 11 inside the bloom, that’s as basic as ammonia solution. We really weren’t expecting to see these levels and such fine-scale changes within the surface layers – they can go from anoxic conditions (low oxygen) to normal levels in less than a centimeter,” Professor Hamilton says.

Using new cryogenic sampling tools which allow samples to be instantly frozen, the team have observed freshwater microbial communities at resolutions never seen before.

“Like a submarine, these cyanobacteria can control their buoyancy. During the day they rise up and form a ‘scum’ on the surface. This is where we see really high pH and oxygen levels – it’s also where toxin production is greatest,” Dr Puddick says.

“We’ve not been able to show these things before because we haven’t been using sampling techniques which enable such a high-definition picture of the natural world.”

The scientists’ next step is to take these new techniques and combine them with other molecular and biochemical tools to understand toxin production at an even finer-scale.

“Right now, using this new technique, we can look at blooms at a millimetre-scale – the next step is to take it to a micrometre-scale and understand how the cyanobacteria are interacting as a community,” Dr Puddick says.

Cryosampling of cyanobacteria (view more videos by CyanoResearch at

As well as novel technologies, the scientists also trialed a different approach by studying toxin production in the field instead of working in the laboratory. The team has spent the last three cyanobacterial bloom seasons at Lake Rotorua in Kaikoura.

“Cyanobacteria kept in the lab don’t respond the same as those found in the natural environment, so we created a lab in the field," Dr Puddick says.

However, working outside did present the team with some difficulties.

“It can be really challenging as there are so many complex things to consider, you don’t get to decide when your experiment starts -  nature is in control. One year we had to contend with a tropical cyclone, there was duck shooting season and then we had an extreme once in 75-year drought.”

Dr Susie Wood (front) and her team studying cyanobacterial blooms in the field at Lake Rotorua, Kaikoura

In the future, the researchers hope to be able to predict toxin production in real time.

“Our ultimate goal is to protect human health by providing governments, councils and regulators with the capability to predict and model the times and regions of highest risk. In the future, this might mean that they have the tools to better inform the public on the safest places to swim at certain times of the day or the week,” Professor Hamilton says.

“We’re not quite there yet, there’s still a lot more we need to understand about toxin production in cyanobacteria, but we’re another step closer now.”

Listen to William Ray interview Dr Wood and Dr Puddick for Radio NZ’s Our Changing World. Click here to read more about their research.

Their recent research using novel cryogenic sampling techniques has just been published in the prestigious scientific journal ‘Limnology and Oceanography: Methods’ and is freely available at: For more information on the team’s research and to keep up-to-date with their latest work, check out their Vimeo channel or follow #CyanoResearch on Twitter.