Cremer: Spatial Distribution otDiatom SUljace Sediment Assemblages
543
shelf (Figure 8). In the southeastern and coastal regions this factor has no importance and factor
loadings are generally low (Table 3). As the species of this assemblage are typical sea-ice
diatoms their distribution may be associated with sea-ice conditions on the Laptev Sea shelf.
Factor 2 (freshwater diatoms assemblage) consists of the freshwater diatoms group and
Aulacoseira spp .. This assemblage dominates the coastal regions of the Laptev Sea and
especially the region east of the Lena delta (Figure 8). In sediments from the central and
northern shelf factor loadings are low. This factor explains 19.9% of the total variance.
Factor 3 (Chaetoceros assemblage) is dominated, in order, by resting spores of Chaetoceros
spp., by Nitzschia spp. (Arctic-marine species, Table 2), and by Thalassiosira hyperborea.
This assemblage is mainly present in the eastern, southeastern, and northeastern parts of the
Laptev Sea shelf (Figure 8) and explains 11.8% of the variance. In some samples of the
western shelf factor loadings of this assemblage are relatively high too.
Table 2: Twenty-one species and species groups (bold-faced) and composition of the species groups used in the
factor analysis of 75 surface sediment samples.
Achnanthes taeniata
Arctic-marine-epibenthic species
Craspedopleura kryophila
Entomoneis gigantea
Entomoneis kjellmannii
Entomoneis paludosa var. borealis
Navicula algida
Navicula directa
Navicula gelida
Navicula glacialis
Navicula imperfecta
Navicula impexa
Navicula kariana
Navicula kryokonites
Navicula lineola var. perlepida
Navicula novadecipiens
Navicula oestrupii
Navicula pagophila
Navicula superha
Navicula transitans
Navicula trigonocephala
Navicula valida
Navicula vanhoeffeni
Pinnularia polaris
Pinnularia quadratarea
Pinnularia semiinflata
Pseudogomphonema arcticum
Pseudogomphonema kamtschaticum
Pseudogomphonema septentrionale
SterlOneis il1conspicua var. baculus
Stenoneis ohtuserostrata
Aulacoscira spp.
Chaetoceros spp. (resting stages)
Coscinodiscus oculus-iridis
Cyciotella spp.
Fossula arctica
Fragilariopsis group
Fragilariopsis cylindrus
Fragilariopsis oceanica
Freshwater diatoms group
Asterionella spp.
Cymbella spp.
Denticula spp.
Diatoma spp.
Didymosphenia spp.
Epithemia spp.
Eunotia spp.
Fragilaria spp. (freshwater species)
Gomphonema spp.
Meridion circulare
Navicula spp. (freshwater species)
Neidium spp.
Pinnularia spp. (freshwater species)
Placoneis spp.
Stephanodiscus spp.
Tabel/aria spp.
Melosira spp.
Navicula peregrina
Nitzschia linearis
Nitzschia (Arctic-marine species)
Nitzschia arctica
Nitzschia brebissollii
Nitzschia delicatisima
Nitzschia geUda
Nitzschia hudsoni;
Nitzschia hybrida
Nitzschia laevissima
Nitzschia lanceolata
Nitzschia polaris
Nitzschia scabra
Nitzschia seriata
Paralia sulcata
Porosira glacialis
ThalaHiosira antarctica/T. gravida
Thalassiosira baltica
Thalassiosira bulbosa
Thalassiosira hyalina
Thalassiosira hyperborea
Thalassiosira nordenskioeldii
543
shelf (Figure 8). In the southeastern and coastal regions this factor has no importance and factor
loadings are generally low (Table 3). As the species of this assemblage are typical sea-ice
diatoms their distribution may be associated with sea-ice conditions on the Laptev Sea shelf.
Factor 2 (freshwater diatoms assemblage) consists of the freshwater diatoms group and
Aulacoseira spp .. This assemblage dominates the coastal regions of the Laptev Sea and
especially the region east of the Lena delta (Figure 8). In sediments from the central and
northern shelf factor loadings are low. This factor explains 19.9% of the total variance.
Factor 3 (Chaetoceros assemblage) is dominated, in order, by resting spores of Chaetoceros
spp., by Nitzschia spp. (Arctic-marine species, Table 2), and by Thalassiosira hyperborea.
This assemblage is mainly present in the eastern, southeastern, and northeastern parts of the
Laptev Sea shelf (Figure 8) and explains 11.8% of the variance. In some samples of the
western shelf factor loadings of this assemblage are relatively high too.
Table 2: Twenty-one species and species groups (bold-faced) and composition of the species groups used in the
factor analysis of 75 surface sediment samples.
Achnanthes taeniata
Arctic-marine-epibenthic species
Craspedopleura kryophila
Entomoneis gigantea
Entomoneis kjellmannii
Entomoneis paludosa var. borealis
Navicula algida
Navicula directa
Navicula gelida
Navicula glacialis
Navicula imperfecta
Navicula impexa
Navicula kariana
Navicula kryokonites
Navicula lineola var. perlepida
Navicula novadecipiens
Navicula oestrupii
Navicula pagophila
Navicula superha
Navicula transitans
Navicula trigonocephala
Navicula valida
Navicula vanhoeffeni
Pinnularia polaris
Pinnularia quadratarea
Pinnularia semiinflata
Pseudogomphonema arcticum
Pseudogomphonema kamtschaticum
Pseudogomphonema septentrionale
SterlOneis il1conspicua var. baculus
Stenoneis ohtuserostrata
Aulacoscira spp.
Chaetoceros spp. (resting stages)
Coscinodiscus oculus-iridis
Cyciotella spp.
Fossula arctica
Fragilariopsis group
Fragilariopsis cylindrus
Fragilariopsis oceanica
Freshwater diatoms group
Asterionella spp.
Cymbella spp.
Denticula spp.
Diatoma spp.
Didymosphenia spp.
Epithemia spp.
Eunotia spp.
Fragilaria spp. (freshwater species)
Gomphonema spp.
Meridion circulare
Navicula spp. (freshwater species)
Neidium spp.
Pinnularia spp. (freshwater species)
Placoneis spp.
Stephanodiscus spp.
Tabel/aria spp.
Melosira spp.
Navicula peregrina
Nitzschia linearis
Nitzschia (Arctic-marine species)
Nitzschia arctica
Nitzschia brebissollii
Nitzschia delicatisima
Nitzschia geUda
Nitzschia hudsoni;
Nitzschia hybrida
Nitzschia laevissima
Nitzschia lanceolata
Nitzschia polaris
Nitzschia scabra
Nitzschia seriata
Paralia sulcata
Porosira glacialis
ThalaHiosira antarctica/T. gravida
Thalassiosira baltica
Thalassiosira bulbosa
Thalassiosira hyalina
Thalassiosira hyperborea
Thalassiosira nordenskioeldii