Fig 7.

A conceptual model showing how information about physico-chemical reference conditions and historical species data can be used to guide management actions. The thick diagonal 1/1 line represents the correspondence between reference and assessment period. The thick dashed line represents the accepted deviation based on physico-chemical criteria. The thin dashed vertical and horizontal line represents physico-chemical threshold for presence of the target organism. Area D is within the accepted deviation from a reference state, whereas in area A and C no biological effect will occur and in area B a significant effect on target organism occurs.