In addition to chemical checks, the presence/absence and abundance of certain freshwater invertebrates (often called macroinvertebrates) – the aquatic larval stage of various insects - can tell a story of a water body’s health. Because some invertebrates are more sensitive to pollutants than others, we can use them as “indicator species”.
Assessing the types of invertebrates found indicates something about the health of the water body they have been found in. For example worms can tolerate high levels of pollutants but some mayflies don’t tolerate even low levels of pollution. They also help describe when pollution events occur because some populations take a while to recover if they have been harmed by pollution.
The Trust is working with Frensham Fly Fishers who have a long-established routine of regular sampling, and we will be working with them to extend the scope of sampling in our branch of the river, combining findings and understanding how and where the river environment and water quality is being impacted.
This supports the Riversearch Wardening scheme run by the Surrey Wildlife Trust.
The Trust monitors water quality using chemical testing and ecology sampling - the current reports are shown below; the most recent return first. Note that wider screen formats allow easier comparison across the sample sessions.