Ecological status of a Mediterranean river (Turon, south of Spain): practical use of biological indexes

摘要

The Water Framework Directive (WFD) 2000/60/EC establishes basic principles of sustainable water policy in the European Union, to maintain and improve the aquatic communities and to protect the ecological integrity of freshwater systems. An integrative analysis of ecosystem properties has become obligatory for river management, so effective and easy-to-use tools that give quick information about the ecological status (the quality of the structure and functioning of aquatic ecosystems) are necessary for successful water management. The nature of river ecosystems involves four dimensions (Ward 1989): longitudinal, lateral, vertical and temporal. Extensive literature reflects that the macroinvertebrate community is the most frequently used biological community for assessing river water quality (e.g., Hynes 1960, Helawell 1986, Rosenberg Resh 1993). A biotic index based on the macroinvertebrate community provides information on longitudinal and temporal dimensions of rivers but provides little information about the lateral and vertical dimensions (Bunn et al. 1999). In order to address this shortcoming, some multiple-dimensional analyses of ecosystem properties, such as the ECOSTRIMED protocol (ECOlogical STatus Rivers MEDiterranean; Prat et al. 2000), include the conservation status of the riparian habitat. An integrated quality value for fluvial ecosystems can then be obtained by combining the values of two quality indices, a biotic index based on macroinvertebrates (FBILL or IBMWP) and the riparian habitat quality index (QBR). Although there are few riparian habitat indexes, the QBR is one of the most-used in Mediterranean areas (SuArez et al. 2002). However, the standard procedure followed to designate the number and location of QBR sampling sites depends, among other factors, on the objectives of the study and the length of the river (with a distance between sites ranging from 1 to 10 kilometres). Considering the high heterogeneity of the Mediterranean landscape, those criteria could induce a loss of information. So, the aim of this study is to analyse the ecological status of a Mediterranean river (Turon, south of Spain) and examine the problems associated with the QBR application.