Ecological classification of the upper part Aliakmon river, Greece.

Well known systems of biological indices applied on benthic macroinvertebrates in European countries (along the Mediterranean coast and elsewhere) were employed to derive the ecological classification and estimate the quality of the upper flow of Aliakmon river and its tributaries. These systems measure the variations of the environmental conditions along the river. They indicate any direct and indirect variations, as well as zones of ecological quality of the waters based on the biocommunity that can be supported by the various habitats. A variety of substantially differentiated benthic communities is observed along the sampling stations on Aliakmon river and its tributaries during the different periods of a hydrological year. This translates into the river being affected by a great variety of anthropogenous activities, and geological structure.