engleski

Key zoobenthos inhabitants as indicators of hydrological dynamics in karst springs

Springs as ecotones and specific autochthonous inland freshwater ecosystems have high integrity and harbor specific species composition caused by various hydromorphological forces and hydrological dynamics. Three karst springs in Croatia were studied in order to assess the influence of various drought regimes on their invertebrate assemblages. The analyzed springs were: Kupa (a limnocrene karst spring with permanent discharge), Majerovo Vrilo (a limnocrene karst spring, one of the Gacka river’s springs that was last documented to have dried up in the 1950s) and Krčić (a descending intermittent karst spring that dries up annually). Four seasonal samplings (of 20 crenozoobenthos sub-samples) were conducted during 2014 with a 200 μm mesh net. Microhabitat coverage was assessed and sub-samples were taken separately and fixated accordingly. The zoobenthos community was analyzed with special emphasis on amphipod (Crustacea: Amphipoda), watermite (Acari: Hydrachnidia) and gastropod (Gastropoda) assemblages and microhabitat preferences. The aims were: to compare temporal aquatic fauna (i.e. watermites) vs. permanent aquatic fauna (i.e. amphipods and gastropods), to emphasize key indicators for temporal vs. perennial springs, and to examine the role of these invertebrate groups in crenozoobenthos composition. Microhabitat preferences (lithal vs. aquatic macrophyte coverage) were also analyzed in order to determine their influence in zoobenthos composition and to assess their ‘refuge’ role in dry phases. This research also brings a comprehensive overview of analyzed springs, including composition, structure and seasonal variations of macroinvertebrates. Diversity and abundance of macroinvertebrates were higher at the perrenial springs than at the intermittent spring. The species composition is highly influenced by characteristics of flow regime, especially by longevity of hydrological permanency. Holistic methods to assess karst spring flows and appearance of key macroinvertebrate inhabitants can help establish the useful tool for target management of springs and spring brooks.

karst springs; crenozoobenthos; Amphipoda; Acari; Hydrachnidia; Gastropoda

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