The complex impact that man has on aquatic ecosystems creates a need for assessment systems that are able to adequately appraise and integrate the effects of various pressures. Chemical analysis alone can easily overlook some factors vital for life. With the adoption of the EU Water Framework Directive (WFD) in the year 2000 which defined the ecological status of surface water as ''... an expression of the quality of the structure and functioning of aquatic ecosystems associated with surface waters", biological indicators were brought to the forefront for the first time and became drivers to the water management practices. Assessment of ecological status and quantification of