538
Land-Ocean SYstems in the Siberian Arctic: Dynamics and History
rivers in the hinterland (Komarjenko and Vasiljeva, 1975). They are transported by the rivers
into the Laptev Sea. The remaining taxa prefer marine or marine-brackish conditions. Most of
the taxa normally inhabit epibenthic and/or epiphytic habitats (272 taxa) whereas only 47 taxa
are typically planktic diatoms. 16 taxa are meroplanktic diatoms which settle in both planktic
and epibenthic environments.
Distribution of ecologically important species
Diatom valves are common in all sediment samples. Total abundance values range from 0.001 x
10 6 to 6.7 x 10 6 valves per gram dry sediment. The distribution of total abundance values is
relatively uneven on the Laptev Sea shelf and does not correlate with any hydrologic or
sedimentologic parameters. The preservation of diatom valves in the surface sediments is
generally moderate to excellent.
In order to document the composition of diatom assemblages in the sediment samples three
west-east-transects have been choosen (Figure 4) along which the relative abundance of the
most important species was determined (Figures 5, 6, and 7). In the following these species
and species groups and their distribution are shortly described.
105 E
110
115
120
125
130'
135
140
145' E
78 N
-
78° N
..r -- - .- ,I
~. . 11 77
,
~ ~
(
I
~ r
..,
L
77
.t ~" -.. "
{
.'
76
75
74
73
S
b
e
72
r
i1
71 N 1
105 E
110
115
120
Figure 4: Map of the Laptev Sea shelf showing three west-east-transects along which the relative abundance of
the most important diatom species and species groups was determined (see Figures 5, 6 and 7).
Aulacoseira spp.: species of this genus are presently known only from freshwater habitats.
Because this genus has great importance in the surface sediments Aulacoseira was counted
separately and not together with the freshwater diatoms group (see below). Three species could
be clearly identified (A. granulata, A. islandica, and A. subarctica) but soleley A. subarctica is
dominant in some coastal samples. Like the other freshwater diatoms Alliacnsl';ra spp. is less
abundant on the two northern transects but is significantly abundant in the region east of the
Lena delta (Figures 5, 6, and 7).
Land-Ocean SYstems in the Siberian Arctic: Dynamics and History
rivers in the hinterland (Komarjenko and Vasiljeva, 1975). They are transported by the rivers
into the Laptev Sea. The remaining taxa prefer marine or marine-brackish conditions. Most of
the taxa normally inhabit epibenthic and/or epiphytic habitats (272 taxa) whereas only 47 taxa
are typically planktic diatoms. 16 taxa are meroplanktic diatoms which settle in both planktic
and epibenthic environments.
Distribution of ecologically important species
Diatom valves are common in all sediment samples. Total abundance values range from 0.001 x
10 6 to 6.7 x 10 6 valves per gram dry sediment. The distribution of total abundance values is
relatively uneven on the Laptev Sea shelf and does not correlate with any hydrologic or
sedimentologic parameters. The preservation of diatom valves in the surface sediments is
generally moderate to excellent.
In order to document the composition of diatom assemblages in the sediment samples three
west-east-transects have been choosen (Figure 4) along which the relative abundance of the
most important species was determined (Figures 5, 6, and 7). In the following these species
and species groups and their distribution are shortly described.
105 E
110
115
120
125
130'
135
140
145' E
78 N
-
78° N
..r -- - .- ,I
~. . 11 77
,
~ ~
(
I
~ r
..,
L
77
.t ~" -.. "
{
.'
76
75
74
73
S
b
e
72
r
i1
71 N 1
105 E
110
115
120
Figure 4: Map of the Laptev Sea shelf showing three west-east-transects along which the relative abundance of
the most important diatom species and species groups was determined (see Figures 5, 6 and 7).
Aulacoseira spp.: species of this genus are presently known only from freshwater habitats.
Because this genus has great importance in the surface sediments Aulacoseira was counted
separately and not together with the freshwater diatoms group (see below). Three species could
be clearly identified (A. granulata, A. islandica, and A. subarctica) but soleley A. subarctica is
dominant in some coastal samples. Like the other freshwater diatoms Alliacnsl';ra spp. is less
abundant on the two northern transects but is significantly abundant in the region east of the
Lena delta (Figures 5, 6, and 7).