Distribution of rotifers and other meiofauna in the bryophytes and hyporheic zone of a karst hydrosystem – an example of a nested community

Abstract

The meiofauna assemblages inhabiting the bryophyte-covered tufa barriers were investigated in the barrage system of Plitvice Lakes (Croatia). The main aims of the present study were: (1) to analyse the structure of the rotifer community and other meiofaunal communities in the bryophytes and the hyporheic tufa zone; and (2) to determine the influence of food sources on the meiofauna. Our results indicate that meiofauna were a constant and abundant component in bryophytes and tufa. Of the nine identified groups (Catenulida, Gastrotricha, Nematoda, Rotifera, Hydrachnidia, Oligochaeta, Copepoda, Tardigrada and Chironomidae (Diptera)), rotifers (50%) and nematodes (40%) were most abundant. Rotifers were the most diverse meiofaunal group and reached their highest numbers within the bryophytes. Also, the highest amount of ultrafine particulate organic matter, as a potential food source for rotifers, was recorded in this layer. Nematodes were the dominant meiofaunal group in deeper tufa layers. They are an omnivorous trophic group and different food sources (such as phytal remains or other meiofauna) were available in tufa layers. Meiofaunal assemblages were significantly nested and their composition was under the influence of community established in surface bryophyte mats. Information on these often overlooked faunal groups is essential for estimates of overall abundance, species richness and productivity in freshwater ecosystems.