Vertical and temporal distribution of free-living nematodes dwelling in two sandy-bed streams fed by helocrene springs

We monitored for 1 year the sediment nematofauna of two headwater streams located near water resurgence from typical helocrene springs. Nematode community composition, benthic organic matter (BOM) and chlorophylla(BChl a) were assessed in two sediment layers (0-5 and 5-10 cm depth), providing insights into nematode vertical distribution. Globally, the density, diversity and functional richness of nematodes were lower in the upper sediments, although important amounts of BChl awere available there. The assemblages differed markedly between springs, with only 41 shared species from a total of 120 species, suggesting stochastic horizontal distribution even at small geographical scales (<5 km). Bacterial-feeding nematodes dominated in the upper sediments, whereas omnivorous, fungal- and plant-feeding nematodes thrived in the deeper sediments. Reproduction by the dominant algal-feeding species,Prodesmodora arctica, was detected in August. The substantial presence of juveniles throughout the year highlighted the importance of parthenogenetic reproduction.

Influence of land use on hyporheos in catchment streams of the Velka Fatra Mts

The historical influence of landscape on the quantitative variables and a special group of hyporheos in streams with similar origin but different catchment landscapes and forest management was studied. The study was conducted in two streams: (i) a preserved forested natural stream where critical ecosystem processes were unaltered by human activities and (ii) a stream with the strong anthropogenic stressors (e.g., logging, agriculture, pasture), impacting the system for the last 500 years. Some parameters were strongly related to these land use: conductivity, fine benthic organic matter (FBOM), orthophosphate (P_PO4) and periphyton content all increased along the gradient from the natural stream to the urban-dominated catchment. The density of interstitial assemblages corresponded with the conductivity (at P < 0.05) and was higher on the stream in urban-dominated catchments; and the Harpacticoida taxa richness, dominated by the family Canthocamptidae, was also greater here. The Multiple Regression Analysis shows that the rate of deforestation had had the most significant effect on the density of hyporheos. Among of crustacean fauna the representatives of epigean harpacticoids from (of) family Canthocamptidae, dominated.