Other language confidence: 0.7970869632804087
Sediment slices of 0.5 cm thickness were obtained from gravity core segments and of 1 cm thickness from the Vydrino piston core. Volumetric subsamples of 5 cm3 (10 cm3 in case of the lowermost samples from Continent core) were prepared according to standard procedures, including 7-μm ultrasonic fine-sieving (Cwynar et al., 1979, Fægri et al., 1989 K. Fægri, P.E. Kaland and K. Krzywinski, Textbook of Pollen Analysis (4th edition), John Wiley & Sons, Chichester (1989) 328 pp..Fægri et al., 1989 and PALE Steering Committee, 1994). Two tablets of Lycopodium marker spores were added to each sample for calculating total pollen and spore concentrations (Stockmarr, 1971). Water-free glycerol was used for storage and preparation of microscopic slides. The palynological samples were counted at magnifications of 400–600×, applying 1000× for the identification of difficult pollen types, e.g., including Saxifragaceae, Crassulaceae, and Rosaceae.
Sediment slices of 0.5 cm thickness were obtained from gravity core segments and of 1 cm thickness from the Vydrino piston core. Volumetric subsamples of 5 cm3 (10 cm3 in case of the lowermost samples from Continent core) were prepared according to standard procedures, including 7-μm ultrasonic fine-sieving (Cwynar et al., 1979, Fægri et al., 1989 K. Fægri, P.E. Kaland and K. Krzywinski, Textbook of Pollen Analysis (4th edition), John Wiley & Sons, Chichester (1989) 328 pp..Fægri et al., 1989 and PALE Steering Committee, 1994). Two tablets of Lycopodium marker spores were added to each sample for calculating total pollen and spore concentrations (Stockmarr, 1971). Water-free glycerol was used for storage and preparation of microscopic slides. The palynological samples were counted at magnifications of 400–600×, applying 1000× for the identification of difficult pollen types, e.g., including Saxifragaceae, Crassulaceae, and Rosaceae.
The studied core CON01-603-2 was recovered from the Continent site, Northern Basin from a water depth of 386 m (Fig. 1) (see Charlet et al., 2005-this volume). The analysed sequence (725.5–608 cm) consists of mainly of biogenic, diatomaceous sediments, although the upper part of the sequence between ca. 611–608 cm contains more silt particles and less diatoms than the lower part of the sequence. From a depth of 690 cm upwards the sediments are finely and coarsely laminated.Based on a standard technique for processing palynological samples, silicates were removed from the sediment by treatment with 40% HF for 3 days and with 50% HF for 1 day. Following Erdtmans acetolysis (Faegri and Iversen, 1989) sediment samples were sieved through 7-µm meshes in an ultrasonic water bath (Cwynar et al., 1979).
Dissolution was high throughout the profile—in most cases, only 10–20% of the valves considered as pristine (Fig. 4). High relative percentages of A. baicalensis and of benthic Fragilaria (sensu lato) were positively correlated (r=0.29 and r=0.26, respectively) to samples with large proportions of pristine valves. There were no significant relationships between this index of dissolution and any of the other dominant taxa. Fragmentation of the valves was also high. On average only 45% of the total count was represented by whole valves (Fig. 4) and high percentages of non-fragmented valves were positively correlated with the percentages of pristine valves. The percentages of pristine valves showed high variation (20–70%) and by contrast with the dissolution index, they were significantly correlated with the variations in percentages of many dominant taxa.
Water content and dry bulk density of pilot core to CON01-603-2
Wet bulk density (GRAPE) of piston core CON01-604-2 from Posolskoe
The vertical distribution of organisms in the sediment indicates that animals can be present as deep as 15 cm although at very low abundance at such depths (Fig. 4, Fig. 5 and Fig. 6). Oligochaetes and nematods are the only groups able to deeply penetrate into the sediment at significant densities (Fig. 4) in contrast to all other groups, which stay closer to the sediment surface. Maximal densities however seem to shift to the sediment surface with increasing bathymetric depth, as suggested in Fig. 5 and Fig. 6, so that all animal groups are more concentrated near the surface in the deepest parts of Lake Baikal. In such case, the depth of sediment mixing due to bioturbation appears to decrease with increasing bathymetric depth (Fig. 2b).
The vertical distribution of organisms in the sediment indicates that animals can be present as deep as 15 cm although at very low abundance at such depths (Fig. 4, Fig. 5 and Fig. 6). Oligochaetes and nematods are the only groups able to deeply penetrate into the sediment at significant densities (Fig. 4) in contrast to all other groups, which stay closer to the sediment surface. Maximal densities however seem to shift to the sediment surface with increasing bathymetric depth, as suggested in Fig. 5 and Fig. 6, so that all animal groups are more concentrated near the surface in the deepest parts of Lake Baikal. In such case, the depth of sediment mixing due to bioturbation appears to decrease with increasing bathymetric depth (Fig. 2b).
The vertical distribution of organisms in the sediment indicates that animals can be present as deep as 15 cm although at very low abundance at such depths (Fig. 4, Fig. 5 and Fig. 6). Oligochaetes and nematods are the only groups able to deeply penetrate into the sediment at significant densities (Fig. 4) in contrast to all other groups, which stay closer to the sediment surface. Maximal densities however seem to shift to the sediment surface with increasing bathymetric depth, as suggested in Fig. 5 and Fig. 6, so that all animal groups are more concentrated near the surface in the deepest parts of Lake Baikal. In such case, the depth of sediment mixing due to bioturbation appears to decrease with increasing bathymetric depth (Fig. 2b).