The water framework directive: water alone, or in association with sediment and biota, in determining quality standards?

Abstract

The European water framework directive (WFD; Directive 2000/60/EC) develops the concept of ecological quality status (EcoQ) for the assessment of the quality of water masses. The EcoQ is based upon the status of biological, hydromorphological and physicochemical quality elements, with biological elements being especially important; and supported by the others. The physico-chemical elements include general variables (such as dissolved oxygen, nutrients, etc.) and specific pollutants. The former correspond to variables measured directly in the water. However, there is no indication about which matrices are to be sampled, or for which specific pollutants. In order to comprehensively assess the ecological status of aquatic systems, all the significant matrices and elements should be addressed, especially those that would most likely affect the biota of the system and those providing relevant information on impacts to them. Sediments are considered to be important in assessment of anthropogenic impacts to coastal and estuarine environments (Ridgway and Shimmield, 2002; Chapman and Wang, 2001). Similarly, biomonitors have been widely used for assessing the contamination of marine ecosystems (Cantillo, 1998; O’Connor, 1998), providing significant information on specific pollutants over relevant resolution time periods. It is highly significant that ‘water’ is referred to on 373 occasions throughout the WFD, but other matrices, such as sediment or biota (biomonitors), are mentioned explicitly only 7 and 4 times, respectively. On at least three occasions the latter two terms are used in con-