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Wahkohtowin explores periphytometer tool in assessing forestry pesticide use.

Updated: Nov 20, 2023

" The Guardians are getting exposure to the tools and science to understand the deep effects of pesticide use on the health of our forests "

David Flood, General Manager, Wahkohtowin Development -


Biochar burner pictured at Hawk Feather Farms. Flames billow from the top of a circular above ground steel pit used for making BioChar.

..... The name comes from it’s ability to collect periphyton, a microbial community encompassed by extracellular polymeric substances......



In the continuing push to eliminate herbicide use in our forests, Wahkohtowin has taken another step to test and monitor the health of our lands and waters. With the guidance of Guelph University PhD candidate Moira Ijzerman, Wahkohtowin staff deployed an ingenious passive sampling device to detect the presence and concentration of fungicides, herbicides and insecticides in streams, lakes and rivers.


The device is called a periphytometer. The name comes from its ability to collect periphyton, a microbial community encompassed by extracellular polymeric substances. The periphyton is continuously exposed to pollutants transported in the water and will collect and briefly hold on to fungicides, herbicides and insecticides. A periphytometer is a cage which holds several acrylic slides that the periphyton will attach itself to, making sample collection possible. Periphyton can also be collected from natural substrates such as rocks and boulders in the water source, however the periphytometer removes the need to have the rocks and boulders present in the water source.


The periphytometers are placed in the water several weeks before an anticipated spray, this allows time for the periphyton to attach itself to the panels and grow. As the periphyton accumulates on the panels, it will ideally trap and retain any pesticides in the water. Wahkohtowin staff have deployed a periphytometer in a stream located near a harvest block scheduled for herbicide spray. Samples have been collected and will be sent to the lab for testing.


To add to our Herbicide Alternative Program, we are using this technology to specifically detect glyphosate in the water from residual herbicide spray. Glyphosate is typically monitored by collecting water samples. However, this is not an effective method to monitor this herbicide because of its chemical composition. Glyphosate is a charged chemical, meaning that when it enters aquatic ecosystems, it rapidly leaves the water column and binds to sediment or periphyton instead. Therefore the use of periphytometers to monitor for the presence of this chemical is more appropriate than collecting water samples. Although a negative result does not mean there is not glyphosate in the water; a positive test result will strengthen our stand to eliminate spraying and open discussions with industry partners to find an alternative solution.


Author - Andrew Orton - Resource Technician - Wahkohtowin Development

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