Microannelids of Western Carpathian spring fens: Do hydro- and pedobiological methods yield different results?
|Popis||Annelids are represented by several families, abundant and of ecological importance both in soil and freshwater sediments. In particular in one family, Enchytraeidae, there is substantial overlap between the annelid fauna of aquatic and terrestrial habitats. However, annelids are usually studied either as part of the aquatic community or as part of the soil community. The traditionally employed methods differ substantially. In difference to other oligochaetous clitellates, enchytraeids are often not identified to species in hydrobiological studies. In the present contribution we present a comparison of microannelid assemblages as reflected by hydrobiological and pedobiological methods of sampling and sample processing. In 2015, annelids were sampled in 14 spring fens (and adjacent grasslands) in the Western Carpathians (Czechia and Slovakia) using pedobiological methods. A few years earlier, the spring fens at these sites had been sampled using a hydrobiological sampling method, and annelids from these samples had been identified. At each site two microhabitats, i.e. spring brook sediments and waterlogged substrate (vegetation/peat), were sampled taking one sample of substrate (625 cm2, 5 cm depth) once in spring and once in autumn. Samples were fixed in formaldehyde and oligochaetes were manually sorted out and identified. The pedobiological sampling included sampling for earthworms and for microannelids. Here we focus on the latter: Per site, five cores of waterlogged substrate were taken in spring and another five in autumn using a soil corer (17 cm2, 12–15 cm depth). Each core was subdivided in 3-cm layers and these stored in plastic bags and kept cool during transport and storage. Microannelids were extracted for 48 hours by the wet funnel method without heating and identified alive. The sampled fens covered all four types distinguished along the mineral rich-poor gradient, but 8 of the 14 sites were mineral-rich fens with tufa formation, whereas the other three types were represented by two to three sites only. Therefore, most comparisons will focus on these 8 sites. The densities obtained by the pedobiological methods were much higher than those obtained by the hydrobiological one (but mind that samples were taken in different years). Employing pedobiological methods, enchytraeids made up for over 87% and 77% and naidids only 9% and 21% of microannelid individuals (Aeolosomatidae excluded) in spring and autumn, respectively. Using hydrobiological methods, enchytraeids made up for 16% and 8% and lumbriculids 78% and 60% (as above) in the fen substrate with standing water. In the brook sediments Lumbriculidae were even more dominant. Due to the very different representation of taxa “uncovered” by the different methods, and the higher number of enchytraeid species found in 2015, assemblages found by the pedobiological and hydrobiological methods were very different. The assemblages in the spring brook sediments showed a somewhat intermediate position between the assemblages found by the two methods in the identical waterlogged fen habitat. The study yielded several noteworthy faunistic records, such as first records of Parergodrilus heideri (“Polychaeta”) for Slovakia.|