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The habitats of Mediterranean rivers. Design of a habitat diversity index

Abstract:

Mediterranean rivers suffer from historical alterations in their watersheds and riparian corridors, and as a consequence their stream habitats are strongly impacted. The river habitat index (IHF) is designed as a response to the need for characterising the physical habitat of Mediterranean streams and rivers within the main objectives of the GUADALMED project. The aim of this project is to evaluate the ecological status of Mediterranean rivers in accordance with the Water Framework Directive (2000/60/EC), the new European Community legislation on water management. The IHF evaluates relations between habitat heterogeneity and physical variables of the stream channel, which are influenced by hydrology and substrate composition. This includes variables such as frequency of riffles, flow velocity and depth regime, substrate diversity and substrate inclusion in riffles and sedimentation in pools. The index also evaluates presence and dominance of heterogeneity elements, which contribute to increasing physical habitat diversity and food sources, among these allochthonous material (leaves, wood), and autochthonous primary producers as presence and dominance of different morphological groups of aquatic vegetation. This study identifies the strong dependence of the biological quality (biotic indices and number of families) on habitat quality (GLM p<0,0001), after elimination of the influence of other co-variables related to general patterns of invertebrate distribution in the studied Mediterranean streams (conductivity, discharge and contamination). The index has good potential for the evaluation of degree of disturbance in Mediterranean rivers through comparison of IHF values characteristic of reference conditions of high ecological status, in line with the objectives, which will be further developed in the following phase of the Project. © Asociación Española de Limnología.