Particle Fluxes and Sédiment Characteristics at Three Selected Sites
213
4 Results
4.1 Sédiment Features
Figure 2 shows the most évident lithologie features of sédiments from visual
description and X-radiographs of cores, and Fig. 3 depicts the grain size distribution in selected sédiment samples (2bcl, 15bc5, 24bc6). According to Anderson
et al. [9] and Dunbar et al. [ 10] the surficial sédiments at sites A and B can be classified as siliceous muds. At site A sédiment is brown and contains pebbles and
gravels (ice rafted débris) below 10-cm depth. The figures show that there are
inhomogeneities among samples, in that surficial sédiments are always a biogenic
mud, whereas below 8-10 cm sédiments of 2bcl are coarser than that of 2bc2. At
site B the sédiment is fine, olive-gray siliceous mud and ooze without gravels.
Here the sédiment is oxic at the surface and becomes sub-oxic below 5-7 cm. The
average bulk dry density at A is lower than at B: 0.56 and 0.65 g cm'3, respectively. At site C residual glacial-marine sédiment is présent, mainly as sand with a
conspicuous amount of pebbles, gravels and biogenic carbonate débris.
4.2 Biogenic Silica, Organic Carbon and Nitrogen
Figure 3 shows the concentration-depth profiles of biogenic components at the
three sites. The content of biogenic silica decreases with depth in core A from 29
to 13%; organic carbon (OC) and N show a similar pattern varying from 1.14 to
0.5% and from 0.18 to 0.06%, respectively. At site B biogenic silica (21-32%), OC
(0.86-1.23%) and N (0.12-0.16%) contents do not decrease significantly with
depth in core. At site C the contents of biogenic silica (0.2-1.6%), OC (0.05-0.19%)
and N (0.01-0.04%) are very low.
4.3 210Pb Profiles
210Pbex activity-depth profiles are shown in Fig. 3. Accumulation rates were calculated only for fine sédiments at sites A and B, since there is no présent sédiment
accumulation at site C [5]. Surficial mixed layers (SML) are clearly visible in
210Pbex profiles relative to sites A and B; their thickness is 6 and 4 cm, respectively (Fig. 3). Below SMLs, profiles decrease nearly monotonically with depth. At site
A, the change of lithology in 2bcl (Fig. 2) clearly affects the 210Pbex activity in the
surficial layer and cause a discontinuity in the profile. The ~10Pbex profile at site C
shows two sections with different slopes.
4.4 Macrobenthos
Figures 4,5 and 6 describe macrobenthos composition abundances and distributions. In fine biogenic sédiments (A and B), benthic fauna is mainly composed of
infaunal sedentary forms, mostly represented by polychaetes (mean dominance
213
4 Results
4.1 Sédiment Features
Figure 2 shows the most évident lithologie features of sédiments from visual
description and X-radiographs of cores, and Fig. 3 depicts the grain size distribution in selected sédiment samples (2bcl, 15bc5, 24bc6). According to Anderson
et al. [9] and Dunbar et al. [ 10] the surficial sédiments at sites A and B can be classified as siliceous muds. At site A sédiment is brown and contains pebbles and
gravels (ice rafted débris) below 10-cm depth. The figures show that there are
inhomogeneities among samples, in that surficial sédiments are always a biogenic
mud, whereas below 8-10 cm sédiments of 2bcl are coarser than that of 2bc2. At
site B the sédiment is fine, olive-gray siliceous mud and ooze without gravels.
Here the sédiment is oxic at the surface and becomes sub-oxic below 5-7 cm. The
average bulk dry density at A is lower than at B: 0.56 and 0.65 g cm'3, respectively. At site C residual glacial-marine sédiment is présent, mainly as sand with a
conspicuous amount of pebbles, gravels and biogenic carbonate débris.
4.2 Biogenic Silica, Organic Carbon and Nitrogen
Figure 3 shows the concentration-depth profiles of biogenic components at the
three sites. The content of biogenic silica decreases with depth in core A from 29
to 13%; organic carbon (OC) and N show a similar pattern varying from 1.14 to
0.5% and from 0.18 to 0.06%, respectively. At site B biogenic silica (21-32%), OC
(0.86-1.23%) and N (0.12-0.16%) contents do not decrease significantly with
depth in core. At site C the contents of biogenic silica (0.2-1.6%), OC (0.05-0.19%)
and N (0.01-0.04%) are very low.
4.3 210Pb Profiles
210Pbex activity-depth profiles are shown in Fig. 3. Accumulation rates were calculated only for fine sédiments at sites A and B, since there is no présent sédiment
accumulation at site C [5]. Surficial mixed layers (SML) are clearly visible in
210Pbex profiles relative to sites A and B; their thickness is 6 and 4 cm, respectively (Fig. 3). Below SMLs, profiles decrease nearly monotonically with depth. At site
A, the change of lithology in 2bcl (Fig. 2) clearly affects the 210Pbex activity in the
surficial layer and cause a discontinuity in the profile. The ~10Pbex profile at site C
shows two sections with different slopes.
4.4 Macrobenthos
Figures 4,5 and 6 describe macrobenthos composition abundances and distributions. In fine biogenic sédiments (A and B), benthic fauna is mainly composed of
infaunal sedentary forms, mostly represented by polychaetes (mean dominance