This guidance standard defines a method for surveying aquatic macrophytes in lakes - primarily for the purpose of assessing ecological status, using these organisms as an element of biological quality. The information provided by this method includes the composition and abundance of the aquatic macrophyte flora. For a complete assessment of ecological status, other elements of biological quality should also be assessed. The general principle of the approach described in this European Standard may also form the basis for the monitoring and assessment of macrophytes in lakes, for example, for conservation purposes.