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Biology

We compare the macro-invertebrates (small animals that can be seen with the naked eye) in the sample with the range of species we would expect to find in the river if it was not polluted and assign a grade. We take into account natural changes that happen such as geology and flow.

Biology

Classification

Description

A - very good

Biology similar to that expected for an unpolluted river

B - good

Biology is a little short of an unpolluted river

C - fairly good

Biology worse than expected for unpolluted river

D - fair

A range of pollution tolerant species present

E - poor

Biology restricted to pollution tolerant species

F - bad

Biology limited to a small number of species very tolerant of pollution