Ecological status classifications can be composed of up to five different assessments:
1. An assessment of status indicated by a biological quality element such as fish, invertebrates or algae.
2. An assessment of compliance with environmental standards for supporting physico-chemical conditions, such as dissolved oxygen, phosphorus or ammonia.
3. An assessment of compliance with environmental standards for concentrations of specific pollutants, such as zinc, cypermethrin or arsenic
And, in determining high status only:
4. A series of tests to make sure that hydromorphology is largely undisturbed
5. An assessment of the presence of invasive species.
Ecological status is recorded as high, good, moderate, poor or bad. ‘High’ represents ‘largely undisturbed conditions’. Other classes show increasing deviation from undisturbed or reference conditions. Ecological status is determined by the worst scoring element (one-out-all-out approach). Attribution statement: © Environment Agency copyright and/or database right 2015. All rights reserved.