Toxic Algae Monitoring 

This page lists results of toxic algae monitoring in the district's rivers. Rivers are monitored at times of risk of algal build up.

Current Status

The Waimea River at River Road and several popular swimming sites are being monitored weekly for signs of toxic algae. Visual estimates of percentage coverage are shown below:

Anatoki at One Spec Rd

Date SampledCoverageComments

 19/12/2017

<1%

 No sign of toxic algae

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Lee River at Lee Reserve 

Date SampledCoverageComments

 08/02/2018

<1%

 No sign of toxic algae

 30/01/2018

<1%

 No sign of toxic algae

 25/01/2018

<1%

 No sign of toxic algae

 23/01/2018

<1%

 No sign of toxic algae

 16/01/2018

<1%

 No sign of toxic algae

 11/01/2018

<1%

 No sign of toxic algae

 09/01/2018

<1%

 No sign of toxic algae

 03/01/2018

<1%

 No sign of toxic algae

 27/12/2017

<1%

 No sign of toxic algae

 21/12/2017

<1%

 No sign of toxic algae

 19/12/2017

<1%

 No sign of toxic algae

 14/12/2017

<1%

 No sign of toxic algae

 12/12/2017

<1%

 No sign of toxic algae

 07/12/2017

<1%

 No sign of toxic algae

 05/12/2017

<1%

 No sign of toxic algae

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Roding River at Twin Bridges

Date SampledCoverageComments

 08/02/2018

<1%

 No sign of toxic algae

 30/01/2018

<1%

 No sign of toxic algae

 25/01/2018

<1%

 No sign of toxic algae

 23/01/2018

<1%

 No sign of toxic algae

 16/01/2018

<1%

 No sign of toxic algae

 11/01/2018

<1%

 No sign of toxic algae

 09/01/2018

<1%

 No sign of toxic algae

 03/01/2018

<1%

 No sign of toxic algae

 27/12/2017

<1%

 No sign of toxic algae

 21/12/2017

<1%

 No sign of toxic algae

 19/12/2017

<1%

 No sign of toxic algae

 14/12/2017

<1%

 No sign of toxic algae

 12/12/2017

<1%

 No sign of toxic algae

 07/12/2017

<1%

 No sign of toxic algae

 05/12/2017

<1%

 No sign of toxic algae

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Takaka River at Paynes Ford

Date SampledCoverageComments
19/12/2017 <1% No sign of toxic algae 
12/12/2017 <1% No sign of toxic algae

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 Waimea River at River Rd 

Date SampledCoverageComments

 08/02/2018

2%

 Majority seen in the riffles

 30/01/2018

1%

 Majority seen in the riffles

 25/01/2018

<1%

 No sign of toxic algae

 23/01/2018

<1%

 No sign of toxic algae

 16/01/2018

<1%

 No sign of toxic algae

 11/01/2018

<1%

 No sign of toxic algae

 09/01/2018

1%

 Majority seen in the riffles

 03/01/2018

1%

 Majority seen in the riffles

 27/12/2017

<1%

 No sign of toxic algae

 21/12/2017

 1%

 Majority seen in the riffles

 19/12/2017

 1%

 Majority seen in the riffles

 14/12/2017

 1%

 Majority seen in the riffles

 12/12/2017

 1%

 Majority seen in the riffles

 07/12/2017

 1%

 Majority seen in the riffles

 05/12/2017

 1%

 Majority seen in the riffles

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Wai-iti River at Brightwater Bridge

Date SampledCoverageComments

 08/02/2018

1%

 Majority seen in the riffles

 30/01/2018

1%

 Majority seen in the riffles

 25/01/2018

<1%

 No sign of toxic algae

 23/01/2018

<1%

 No sign of toxic algae

 16/01/2018

<1%

 No sign of toxic algae

 11/01/2018

<1%

 No sign of toxic algae

 09/01/2018

2%

 Majority seen in the riffles

 03/01/2018

1%

 Majority seen in the riffles

 27/12/2017

<1%

 No sign of toxic algae

 21/12/2017

1%

 Majority seen in the riffles

 19/12/2017

1%

 Majority seen in the riffles

 14/12/2017

1%

 Majority seen in the riffles

 12/12/2017

<1%

 No sign of toxic algae

 07/12/2017

<1%

 No sign of toxic algae

 05/12/2017

<1%

 No sign of toxic algae

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About the Sampling

The Ministry for the Environment (MfE) cyanobacteria guideline survey method is being used for assessment. Ministry guidelines state that warning signs should be put up around rivers where the percentage coverage of toxic algae is above 20%.

Where levels are below 20% and there is no need for warning signs. We would still recommend that the public keep an eye on children and dogs near the water - don’t let them eat any algae.

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Risks of Toxic Algae 

During extended summer low flows some naturally-occurring blue green algae (cyanobacteria) can increase cover of the stream bed and produce toxins which, if consumed in high enough quantities, can cause illness or death. Phormidium is the main toxin-producing cyanobacteria.

A confirmed toxin-producing blue-green alga was present in the lower Waimea River in January 2014. Other rivers in Tasman District had toxin producing algae during the 2012/2013 summer season. As a result of this, the rivers are being monitored for the presence of blue-green algae and the results are shown below.

In Tasman District there have been no cases of human sickness or death due to toxic algae. However, there have been several recent cases of dog death where toxic algae was suspected as the cause. Dogs, puppies in particular, are most vulnerable to these toxins because they will drink from rivers and consume algae either attached to the riverbed or floating. One case, in late January 2013, occurred when the coverage of toxic algae on the bed was very low (2.5%), which suggests that there is a risk to dogs at almost any time.

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