Do intermittent and ephemeral Mediterranean rivers belong to the same river type?

The benthic macroinvertebrate communities and ecological quality of eleven temporary rivers (seven intermittent and four ephemeral) in Dadia National Park, north-eastern Greece, were examined with respect to the degree of flow temporality. Sampling took place during the high flow season at both ephemeral and intermittent sites and during the low flow season only at the intermittent ones, which receded to pools. Despite the remarkable seasonal variation in both the hydrology and ecology of the intermittent rivers, the various metrics and indices as well as the multivariate analyses confirmed the clear distinction between the two river types (ephemeral and intermittent). Existing European quality indices do not sufficiently differentiate between ephemeral and intermittent river types, and thus cannot reliably discriminate the degree of natural variability from human induced stressors in temporary rivers.