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Emergence patterns and ecological features of stoneflies along an oligotrophic hydrosystem

Stoneflies (Plecoptera, Insecta) are important components of freshwater assemblages, especially in running waters. They are important water quality indicators since they are one of the most sensitive groups of freshwater invertebrates to water pollution, occuring mostly in clean, oxygen-saturated waters. This study was conducted in Plitvice lakes National Park. representing a wide variety of freshwater habitats (springs, streams and tufa barriers). Adults were collected monthly from February 2007 until December 2008 using pyramid-type emergence traps at 9 locations. A total of 14099 individuals belonging to 33 species representing 4 families were recorded. Higher number of species, but lower abundance of stoneflies was recorded during 2008. The dominant species on the higher altitude sites was Protonemura auberti, while for lower altitude sites these were Protonemura intricata and Amphinemura triangularis. Considerable differences in composition and structure of Plecoptera assemblages were recorded along a longitudinal gradient of studied sites, primarily related to differences in physical and chemical parameters of water. Water temperature and pH were the main factors influencing the composition and structure of Plecoptera assemblages. All recorded species were univoltine with emergence peaks recorded during May and June. A statistically significant positive correlation between the abundances and flow velocity of water was found for P. auberti, P. intricata and P. praecox and most pronounced for Leuctra fusca. A. triangularis, P. intricata and P. praecox preferred moss-mats habitats. On the other hand, they scarcely inhabited macrophytes on the sandy substrate or were not present at all. This study is one of the first detailed studies of stonefly assemblages in Plitvice lakes National Park thus representing an important contribution to the knowledge of their ecology along oligotrophic hydrosystems.

Plecoptera, emergence, ecological features

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