Monitoring periphyton in rivers

Periphyton is the brown or green slime that grows on stones, wood or any other stable surfaces in streams and rivers. In some situations, it can form simple mats, while at other times it can flourish to form thick masses of green or brown filaments on the riverbed. Periphyton communities are complex and can include a mixture of algae, cyanobacteria, diatoms, didymo, fungi and detritus (dead organic matter).

Periphyton is the main source of food for invertebrates, which themselves become food for fish, birds and reptiles. It also purifies water by absorbing nutrients. However, if periphyton grows too much it can affect habitat for invertebrates and fish, alter oxygen levels available in the water and degrade the aesthetic (visual) and recreational qualities of the river. Cyanobacteria (also known as toxic algae) blooms can be a risk to human health.