Comparison of aquatic interstitial invertebrate communities in Sava River, Slovenia

Spomladi 2015 smo vzorčili nevretenčarje intersticiala reke Save na dvanajstih prodiščih med Medvodami in mejo s Hrvaško. Uporabili smo metodo vzorčenja z Bou-Rouch črpalko ter pridobili obsežne podatke o intersticialni favni Save. Na vsaki lokaciji smo po trikrat vzorčili 30 litrov vodnega vzorca, vsakič s treh globin: plitek hiporeik med 30 in 60 cm globine ter globoki hiporeik med 60 in 90 cm globine, slednjega enkrat v vodi in enkrat na bregu reke. V Kresnicah smo testirali učinkovitost metode vzorčenja in količino vodnega vzorca tako, da smo ločeno nabrali 10 in 20 litrov na ponovitev. Pregledali smo nevretenčarje iz frakcij zgoščenih na 0,5 mm mreži in vse osebke določili do prepoznavnih taksonomskih nivojev, kjer smo posebej beležili stigobionte. Med seboj smo primerjali števila taksonov in števila osebkov iz različnih količin vzorcev, hiporeikov in lokacij. Ugotovili smo, da je za splošen pregled favne prodišča dovolj črpanje 10-litrskih vzorcev iz plitkih hiporeikov, za zaznavo večine stigobiontov pa je potrebno črpanje tudi iz globljih plasti. V plitkem hiporeiku smo skupno našli največ taksonov, stigobiontskih vrst pa je bilo številčno enako v vseh treh hiporeikih. Po številu osebkov so v vseh hiporeikih dominirale žuželke. Najbolj vrstno bogate lokacije – tudi s stigobionti – so bile v zgornjem in še posebej v spodnjem delu vzorčenega odseka Save, v osrednjem delu pa smo našli manj taksonov zaradi nedostopnega terena in verjetnega vpliva niza hidroelektrarn ter onesnaženosti reke. Tekom vzorčenja smo našli tudi nove vrste za Slovenijo in znanost.In spring 2015 we sampled invertebrates of the Sava River interstitial from twelve gravel bars between Medvode and the Croatian border. We used the Bou-Rouch pump sampling method and collected extensive data on the interstitial fauna of the Sava River. We collected nine samples per site – three 30-liter samples of each of the three types of hyporheic habitat: shallow hyporheic zone (30 to 60 cm deep), deeper hyporheic zone and gravel bar (both 60 to 90 cm deep). In Kresnice, where we tested the sampling method and the sample volumes, we collected 10 and 20 liters per sample separately. Invertebrates from the 0.5 mm mesh size fractions were sorted and identified to the lowest taxonomic level possible with special attention given to stygobionts. We compared taxa numbers and specimen numbers from different sample volumes, hyporheic types and locations. Results showed that for a general overview of the interstitial fauna, extraction of 10l samples from shallow hyporheic is sufficient, whereas detection of most stygobionts require extraction from deeper layers as well. Overall, the shallow hyporheic was the most taxa rich, while the number of stygobiont species was similar in all types of hyporheic. In terms of number of specimens, insects were the most abundant in all types of hyporheic. The most species-rich locations were in the upper and in the lower sampling section, while few taxa were found in the middle part due to inaccessible terrain and probably also due to a series of hydroelectric power plants and pollution. We also found species new to Slovenia and to science