Meiobenthic assemblages of moraine and tundra reservoirs of Coraholmen Island (Central Spitsbergen) and their differences

The aim was to estimate the diversity of contemporary meiobenthic communities of selected water reservoirs of Coraholmen Island (Central Spitsbergen), and to identify abiotic and biotic factors influencing their diversity. The landform of Coraholmen is unique: the eastern part is flat and overgrown with tundra, while the south-western part is dominated by postglacial moraine hills, between which small water reservoirs are located. Different nature of the bottom surface allows determining the abiotic factors influencing the composition and diversity of meiobenthos. The moraine reservoir's substrate was deposited by glacier and is characterized by accumulation of marine fossils, mainly calcareous benthic foraminifera, brand tills with gravels, and pebbles. Tundra reservoirs (often periodic/astatic) are characterized by accumulation of sandymuddy sediments with rich content of organic matter. Sediment samples were collected from 10 reservoirs. All had low salinity; meiobenthic assemblages found were typical for freshwater reservoirs of Spitsbergen. TN concentration was 328–1004 µg/l, TP 3.2–43.1 µg/l, average value of 522 and 11. TN/TPmol ratio ranged 52–300, increasing with a clearly stronger decrease in phosphorus concentration. Molar ratios of TN/TP mol obtained in tundra ponds were on average twice as high as in the moraine ponds. The examined epibenthic assemblages from all reservoirs were of low diversity. Meiobenthic assemblages were represented by 9 major taxa: Rotifera, Nematoda, Gastrotricha, Oligochaeta, Cladocera, Copepoda, Ostracoda, Diptera larvae and Arachnidae. Ostracoda and Diptera larvae were relatively numerous. The most numerous crustaceans were Ostracoda: Candona rectangulata Alm, 1914 Tonnacypris glacialis, G.O. Sars and Limnocytherina sanctipatricci. The topography, geology, and soil characteristics of the catchment area do not influence the aquatic ecosystem.