Are Intermittent Rivers in the Karst Mediterranean Region of the Balkans Suitable as Mayfly Habitats?

Abstract

Intermittent rivers, common in dry parts of the world, such as the Mediterranean region, are hydrologically harsh habitats characterized by periodical flow cessation. Ephemeroptera are aquatic insects common in both lotic and lentic waterbodies, where they show a high sensitivity to anthropogenic modifications of their habitat. Therefore, they are widely used as bio-indicators of the freshwater’s health. However, mayfly assemblages and their ecological requirements in the karst Mediterranean intermittent habitats are still not sufficiently known. Thus, the work presented here includes an analysis of mayfly assemblages and their relationship with environmental variables in the lotic phase of four intermittent rivers in the karst Mediterranean region of Croatia. Considering that the studied intermittent rivers are hydrologically extreme environments, a total of 12 recorded mayfly species could be considered as rather high species richness. Nevertheless, species richness per river was quite low (between three and six), and was highly influenced by river morphology, physico-chemical water properties (especially conductivity, water velocity, and concentrations of dissolved oxygen), and anthropogenic pressures. Our results could contribute to the mayfly species protection in karst Mediterranean intermittent freshwater habitats in the Balkans, as well as to the development of conservation measures for those threatened habitats.