The meiofauna has been studied in multiple corer samples collected from seven stations in the Arctic Ocean (the Lomonosov Ridge, the Amundsen Basin and the Morris Jesup Rise). Samples were taken at depths ranging between 1072-4273 m. The meiofauna and nematode communities have been analyzed by two classification techniques: Two Way Indicator Species Analysis (TWINSPAN) and Group-Average Sorting using the Bray-Curtis index of similarity) and ordination technique: Canonical Correspondence Analysis (CCA). The nematode structure such as composition, diversity, size structure, sex ratio and feeding type are investigated. No significant difference in the nematode densities could be detected between the seven stations in the Arctic Ocean. The mean meiofauna density is lower than in other areas, ranging from 76 ind./10 cm² at 1847 m to 272 ind./10 cm² at 1072 m. The density and biomass of the nematodes are decreasing with increasing water depth. The Foraminiferan density increases with increasing water depth. The density of meiofauna is positively related to bacteria density and biomass. On the contrary, it is not related with chlorophyll values. The density of nematode is positively related to chlorophyll, bacteria density and biomass. Most of the animals are found in the uppermost centimeter of the sediment and the their densities decrease with increasing depth into the sediment. Multivariate analyses of meiofauna and nematodes show that both meiofauna and nematode communities are quite homogeneous in the seven stations of the Arctic Ocean. The nematode communities are dominated by species of the families Monhysteridae, Linhomoeidae, Chromadoridae and Leptolaimidae. Monhystera has the highest density followed by Metalinhomoeus, Leptolaimus and Acantholaimus.Diversity of the nematodes communities decreases with increasing depth into the sediment. The size of the nematodes tend to decrease with increasing water depth but not significant as much as the increase in number in the smaller size fractions. Nematode are not clearly longer in the deeper sediment in contrast to other studies. This might be caused by the high amount of oxygen in the deeper layers of deep-sea sediments. Most of the nematodes which are retained on the 125 and 250 µm mesh are adults. At the smaller mesh (32 and 63 µm) the number of adult increases with increasing water depth. The non-selective deposit feeders (1B) are the most abundant group at all stations caused by the occurrence of Monhystera. The selective deposit-feeders (1A) and epigrowth feeders (2A) are the second and the third rank. The predator-omnivores (2B) are very rare and in low numbers. If 63 µm mesh is used as the lower limit, 33- 75% of meiofauna and > 50 % of nematode will be lost. So it can be suggested that in the investigation of deep-sea meiofauna one should use 32 µm mesh as the lower limit. The relationship between nematode, water depth and size classes in relation to food availability are discussed. The meiofauna and nematode density are compared with other areas.
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