Assemblages of adult Odonata were studied in four intermittent karst rivers encompassing macrophyte-rich (MRH) and macrophyte-poor habitats (MPH) in southern Europe, where temporary lotic habitats are the predominant freshwater type but are still understudied. With a total of 25 recorded species, the studied habitats support species-rich Odonata assemblages, as already shown for intermittent rivers in the Mediterranean. Aquatic macrophyte abundance, conductivity, and water velocity are the most significant determinants of Odonata assemblages in the studied IRES. MRH promote higher Odonata abundance and the taxonomic and functional diversity of their assemblages compared to the MPH. Odonata assemblages in MRH are characterized by higher values of body size and a higher share of species preferring lentic and temporary hydrological conditions. Moreover, their assemblages are characterized by various patterns of nymphal development and drought resilience strategies. In contrast, MPH are preferred by lotic species, with nymphal development all year round and with no specific drought-resisting strategies. Our results contribute to the knowledge of diversity and ecological requirements of dragonflies and damselflies in IRES habitats, which could provide scientific background for future conservation activities and bioassessment protocols of such habitats and their biota.

Wydawnictwo Naukowe Uniwersytetu Szczecińskiego

Freshwater snails inhabit a wide range of freshwater habitats, including the intermittent ones, specific adaptations enabling them to survive the dry phase for an extended period of time. Despite an increasing scientific interest in biota occurring in intermittent freshwater habitats, our knowledge about environmental factors shaping freshwater gastropod assemblages in such habitats is still poor. Therefore, this study aimed to assess gastropod assemblage composition in four karst intermittent rivers in the Mediterranean during the lotic phase, compare gastropod taxa richness and abundance among the rivers, and determine their relationships with environmental variables. A total of six taxa was recorded, with each river harbouring a unique, species-poor (up to three species) assemblage. Gastropod assemblages were influenced by the physico-chemical water properties, especially the concentration of dissolved oxygen in water, conductivity, and chemical oxygen demand. Our results provide a basis for further research on freshwater snail assemblages in the Mediterranean karst intermittent rivers, as the need to protect these vulnerable ecosystems and develop adequate monitoring practices becomes imperative due to climate change and anthropogenic pressures.

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.