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

The aim of the study was to estimate the diversity of contemporary meiobenthic communities of selected water reservoirs of the small island of Coraholmen (Central Spitsbergen), and to identify abiotic and biotic factors influencing their diversity. The landform of Coraholmen is unique: the eastern part is flat and covered with tundra, while the south-western part is dominated by postglacial moraine hills, between which small water bodies are located. Different nature of the bottom surface allows determining the abiotic factors influencing the composition and diversity of meiobenthos. Sediment and water samples were taken from 10 reservoirs, equally from tundra and moraine areas. The moraine reservoir's substrate was deposited by glacier and is characterized by accumulation of marine fossils, mainly calcareous benthic foraminifera, till with gravels and pebbles. Tundra reservoirs (often periodic/ astatic) are characterized by accumulation of sandy-muddy sediments with rich content of organic matter. The waters in these reservoirs were characterized by low salinity and alkaline pH. The concentration of TN ranged from 328 μg/l to 1004 μg/l, the concentration of TP from 3.2 μg/l to 43.1 μg/l, and the ratio of TN/TPmol ranged from 52 to 300. The molar ratio of TN/TP obtained in tundra ponds was on average twice as high as in moraine ponds. The meiobenthic assemblages found were typical of the freshwater reservoirs of Spitsbergen. 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.