Testate amoebae and diatoms in the Zackenberg area (Northeast Greenland): A study of their assemblages, recent ecology and palaeo-ecology in a High Arctic region

This thesis fits in the long-term monitoring program of Zackenberg (ZERO), which is started up in 1996. The objective of this monitoring program is to provide long-time series of data on the natural oscillations and plasticity of a High Arctic ecosystem.; The thesis deals with two types of organisms: testate amoebae and diatoms. These protists are studied in three major habitat types: soils, terrestrial mosses and aquatic environments. In each habitat type three major points are handled. Firstly the species composition is considered. Secondly the organisation of these taxa in assemblages are studied by means of classification (TWINSPAN) and ordination techniques (PCA, CA, DCA). Further the relation of these assemblages with environmental parameters is treated through ordinations (RDA, CCA) and weighted averages. In a last chapter testate amoebae and diatom composition are analysed in different cores from the Zackenberg region.; In the 3 different habitat types 77 different testate amoebae taxa and 244 diatom taxa are observed. A comparison of the testate amoebae in the different habitats yielded some indicator taxa. Plagiopyxis callida and P. declivis are restricted to the soils. Assulina muscorum and Corythion dubium occur typically in terrestrial mosses. Diflugia globulosa and D. penardi show preferences for aquatic samples. Typical diatom taxa in soil samples and the driest terrestrial mosses are: Diadesmis spp., Hantzschia amphioxys, Navicula atomus, Pinnularia borealis, P. curticostriata and P. obscura. Achnanthes minutissima, A. petersenii, F. pinnata var. pinnata and Tabellaria flocculosa show clear preferences for aquatic samples. Caloneis arctica, Eunotia fallax and Nitzschia perminuta have a high relative abundance in moss samples.; Both the testate amoebae and diatom composition in the oldest sampled core (lower sample dated at 5790 BP) found in the Zackenberg area remarkably changes. The recent ecological information is used to interpret the paleo-environment. The species composition of the samples from the oldest part of the core indicate an aquatic environment at the sampling site. In more recent samples, a zone is noted characterised by testate amoebae and diatom species indicating a vegetation of wet terrestrial mosses. In the most recent samples, taxa able to tolerate extreme dry conditions are dominant.