Other language confidence: 0.7970869632804093
Greigite levels in glacial sediments cannot be correlated between cores (Fig. 12), which suggests that greigite concentrations are driven by local processes. We suggest that faecal pellets could be a suitable microenvironment for sulphate reduction. And while greigite could potentially act as proxy for faecal pellets in glacial sediments, unfortunately, we cannot rely on this possible indicator since the greigite is very sensitive to onshore alterations after sampling (Snowball and Thompson, 1990).
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).
Pollen counts from Kasten corer CON01-603-5 at CONTINENT Ridge.
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.
In all abyssal stations, densities are never over an average of c. 3100 individuals m−2 (Fig. 3, Table 1). In contrast, the shallow station (CON01-427, Posolskoe Bank) harbours the highest observed densities (oligochaetes reach densities as high as 13573 individuals m−2 on average). Gammarids are present in this latter station at 128 m deep, while they are absent from all deep stations. The presence of some groups is anecdotal, such as Hydrachnidia (one specimen in a core at 388 m and two specimens in a core at 625 m) and chironomid larvae (two larvae in a core at 625 m). Interestingly, the two deepest Vydrino cores (CON01-105-7, 600 m, and CON01-106-3, 700 m) are virtually free from animals, suggesting that these stations are perhaps the best choice for the study of stratigraphy and climate proxies.
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.