Temporal dynamics of meiofauna communities in two small submountain carbonate streams with different grain size

The meiofauna community (especially nematodes, oligochaetes and chironomids) in the streambed surface of two small submountain carbonate streams (Krähenbach and Körsch, Germany) was investigated from April 1998 to March 1999. The Krähenbach stream is relatively sorted and fine-grained, while the Körsch stream is more heterogeneous and coarse-grained. The streams also differ in velocity, water level, conductivity, chloride concentration and organic content of sediment. Total meiofauna density reached a maximum value of 906 individuals per 10² cm in the Krähenbach and 3166 individuals per 10² cm in the Körsch. Rotifers were the most abundant group in the Krähenbach (52% of total fauna), whereas nematodes were dominant in the Körsch (63%). Meiofauna showed one abundance peak in the Körsch and two abundance peaks in the Krähenbach. In the Krähenbach, distinct seasonal patterns at family and species level occurred, whereas in the Körsch even at high taxonomic level only one abundance peak was observed. The most abundant nematode family in both streams were Monhysteridae, followed by Tobrilidae in the Krähenbach and by Tylenchidae in the Körsch. The dominant oligochaete family in both streams were Naididae (especially Chaetogaster langi (Bretscher, 1896) and Nais elinguis (O. F. Müller, 1773)), followed by Tubificidae. The most abundant chironomid genera in the Krähenbach were Stichtochironomus and Corynoneura. Prodiamesa olivacea (Meigen, 1818) was the dominant chironomid species in the Körsch. Deposit-feeding and detritus-feeding animals were numerically dominant in both streams. The increased mean abundance of Diplogasteridae, Rhabditidae, Tubificidae and N. elinguis in the Körsch compared to that in the Krähenbach indicates an organically enriched situation.