-Remarkably, unlike other parts of Europe, the ecology of mayflies in the southeastern regions is still poorly known. Here we present the first comprehensive study of Ephemeroptera in the tufa-depositing habitats of the Dinaric Karst. The study was conducted in Plitvice Lakes National Park monthly during a one-year period (2007)(2008) in different types of habitats (springs, streams, mountainous rivers, tufa barriers). The aims of the study were to determine mayfly composition, abundance, spatial distribution and habitat preferences, and to examine the environmental factors important for the structuring of mayfly assemblages in Plitvice Lakes National Park. The mayfly fauna of tufa-depositing habitats was composed of 14 species (20 taxa). Water temperature, pH and ammonium concentration were the most important environmental variables explaining mayfly assemblages. Mayfly assemblages grouped according to habitat type. Generally, the most favourable habitat type was mountainous stream, tufa barriers were less favourable, and the least favourable were springs. Our results confirmed that mayflies are a powerful tool as descriptors of their environment, as the presence or absence of certain mayflies was strongly influenced by physico-chemical water properties.Keywords: case study / ecology / abiotic factors / Ephemeroptera / Southeast Europe Résumé -Facteurs environnementaux influençant la composition des éphémères dans les tufières du Karst Dinarique. De manière surprenante, et contrairement à d'autres parties de l'Europe, l'écologie des éphémères de la zone sud orientale est encore largement inconnue. Dans ce travail, nous présentons la première étude approfondie des éphémères habitant des tufières. L'étude a été menée au Parc National de Plitvice Lacs durant un an (2007)(2008) dans différents types d'habitats (sources, ruisseaux, rivières montagneuses, barrières de tuf). Les objectifs de cette étude étaient de déterminer la composition, l'abondance, la distribution spatiale et les habitats préférentiels des éphémères, d'une part, et d'examiner quels facteurs environnementaux étaient responsables de leur structuration, d'autre part. La faune des éphémères des tufières est composée de 14 espèces (20 taxons). La température de l'eau, le pH et la concentration en ammonium sont les variables environnementales les plus importantes qui expliquent la composition des éphémères. Celle-ci est fonction des types d'habitats. De manière générale, le type d'habitat le plus favorable est celui représenté par les ruisseaux, suivi par les barrières de tuf, les sources étant les moins favorables. Les résultats confirment la puissante capacité des éphémères à décrire leur environnement, puisque la présence ou l'absence de certaines espèces est fortement influencée par les propriétés physico-chimiques de l'eau.
Knowledge of the mayfly biodiversity in the Balkan Peninsula is still far from complete. Compared to the neighbouring countries, the mayfly fauna in Croatia is very poorly known. Situated at the crossroads of central and Mediterranean Europe and the Balkan Peninsula, Croatia is divided into two ecoregions: Dinaric western Balkan and Pannonian lowland. Mayflies were sampled between 2003 and 2013 at 171 sites, and a total of 66 species was recorded. Combined with the literature data, the Croatian mayfly fauna reached a total of 79 taxa. Of these, 29 species were recorded for the first time in Croatia while 15 species were not previously recorded in Dinaric western Balkan ecoregion. Based on the mayfly assemblage, sampling sites were first structured by ecoregion and then by habitat type. In comparison with the surrounding countries, the Croatian mayfly fauna is the most similar to the Hungarian and Bosnian fauna. Some morphologically interesting taxa such as Baetis cf. nubecularis Eaton, 1898 and Rhithrogena from the diaphana group were recorded. Ephemera cf. parnassiana Demoulin, 1958, the species previously recorded only from Greece, was also recorded.
The influences of river regulations on aquatic biota are insufficiently investigated. We assessed the level of ecological disturbance of the mayfly assemblages through the damming and flow alterations at two highly regulated Mediterranean rivers in Croatia: the Cetina River and its tributary, the Ruda. Contrary to our hypotheses, species richness, abundance and diversity of mayflies increased along the river’s course. At the sites directly influenced by the river regulations, mayfly assemblage changed: it was less diverse and less abundant. However, no obvious influence of the river regulation on the mayfly assemblages was detected for the sites that were indirectly influenced by these alterations. This was most likely due to specific karst hydrology, i.e., the presence of lateral springs along the course of the river. Multidimensional scaling analysis (MDS) revealed grouping of sites according to the similarity in physico-chemical water properties. The pH and water temperature were the most important environmental variables influencing mayfly assemblages. The data on ecology and distribution of mayflies presented in the current study represent a valuable background for further research and conservation practices in the Mediterranean region.
Man-made freshwater habitats have been widely used to successfully modify the environment for human benefit, including purposes of irrigation, flood control or electricity generation. Over the past decade, our knowledge about the mayfly fauna and its ecology in South-East Europe has been growing, yet the data related to lentic assemblages remain very scarce. In this study, littoral mayfly assemblages were investigated at artificial and heavily modified lentic habitats in the Dinaric Western Balkan (n=21) and Pannonian Lowland (n=15) ecoregions. Mayfly nymphs were sampled during the summer months of 2016 or 2017. At each sampling site, ten samples were collected using a benthos hand net. A total of 21 mayfly species were recorded, though species richness per site was rather low (i.e., between zero and seven species). Cloeon dipterum (Linnaeus, 1761) was the most frequent species recorded, while Caenis horaria Linnaeus, 1758 was the most abundant. This study showed that the Croatian mayfly fauna is still growing, with the first record of Siphlonurus aestivalis Eaton, 1903 for the country. The assemblage structure was mainly dominated by lower reaches and lentic (potamal and littoral) elements and detritivores (gatherers/collectors and active filter feeders). Orthophosphates and chemical oxygen demand had the highest influence on mayfly assemblages, reflecting a higher level of pollution at sites in the Pannonian Lowland ecoregion, and consequently markedly lower mayfly abundances. As mayflies are widely used as bioindicators of freshwater ecosystems, detailed information about their assemblages in heavily modified and artificial habitats could contribute to future conservation activities of freshwater habitats and their communities. Additionally, these results could be applied in creating a monitoring system for artificial lakes according to the requirements of the European Water Framework Directive.
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