In June (2013) we had a number of pupils from Bradford and Wakefield schools come and sample the Cod Becks aquatic invertebrates as part of their coursework. Sampling was done on Sowerby Flats and below the sewage works. Their work showed a biotic index of 6.4 (Good) for the flats and 4.8 (Medium, but not too bad) below the sewage works.
Mick Dunne reports on the day.
Biological Monitoring of Cod Beck: How clean is our stream?
On Wednesday 19th June 28 Y9 pupils,15 from a school in Bradford and 13 from a Wakefield school four teachers, one teacher trainee, Nigel and I met to carry out a biological survey of Cod Beck. It was suggested that the pupils are environmental scientists that have the responsibility of measuring the water quality of Cod Beck, a small river that joins the River Swale a few miles downstream of where we will carry out our survey. They were told the Cod Beck flows mainly through agricultural land so suffers from agricultural pollution such as fertiliser run off, but also more worrying is that treated water from sewerage plants also enters the Beck at different points, Sowerby being one such place.
Both groups were provided with further contextual information about freshwater invertebrates, how to sample and how the numbers and types of animal will vary with water quality and that we can use this idea to produce what is called a Biotic Index, a number indicating how clean the water is. They were told how to collect and identify their specimens using a field guide, how to record and calculate the index.
These young people and their teachers supported by Nigel and myself worked with great enthusiasm and although some wellies were filled with water they had a great time. Twelve samples below the sewage outfall gave an average biotic index of 4.8 whereas five samples around the Flats gave an average biotic index of 6.4. Even allowing for difficulties with identification such data is indicative of a difference in water quality although we recognise the need for more reliable data. Nevertheless this was a useful exercise and hopefully the beginning of a longer term monitoring effort.
Listed below are some of the groups of aquatic invertebrates the students found.
|Burrowing mayfly nymphs|
|Flattened mayfly nymph|
|Swimming mayfly nymph|
|Other damselfly nymphs|
|Cased caddis fly larvae|
|Caseless caddis fly larvae|
|Non-biting midge larvae|