Particle Fluxes and Sédiment Characteristics at Three Selected Sites
217
sédiment layers
Fig. 6. Abundance of macrozoobenthic organisms in different sédiment layers. Mean values are reported (number of individuals of 0.1 m-2), and bars represent standard déviations (sites B and C) or intervals between minimum and maximum values (site A)
ripeds (barnacles), amphipods and tanaids (47.5%). Infaunal polychaetes (31.3%)
and bivalves (3.3%) are much less represented with respect to the other sites. The
large amount of organogenous dead remains présent in this sédiment is composed of recent and sub-fossil tests of various benthic organisms. The most conspicuous and abundant remains were the tests of the deep-water barnacles of the
genus Bathylasma (a few of them were also found alive) and mollusc gastropods
of the genus Trophon (Muricidae). Dead skeletons of solitary and colonial
madreporarians, bryozoans and tubes of serpulid polychaetes were also abundant. Such dead remains were also présent on pebbles and tests of barnacles. The
dimensions of both dead and living organisms were generally relatively small,
probably due to the prevalence of young individuals. With respect to the replicates
of site B, this site is characterised by higher variability and patchiness in the composition of living fauna.
Faunal density (Fig. 5) showed the highest mean value at site B with more than
1000 individuals m"2, followed by site C (ca. 500 individuals m’2) and site A (430
individuals m'2). These values, which are the first available for the deep sédiment
of the Ross Sea, are from one to two orders of magnitude lower than those recorded at shallow depth in other soft bottoms of the Ross Sea, such as McMurdo Sound
[18] and Terra Nova Bay [19].
217
sédiment layers
Fig. 6. Abundance of macrozoobenthic organisms in different sédiment layers. Mean values are reported (number of individuals of 0.1 m-2), and bars represent standard déviations (sites B and C) or intervals between minimum and maximum values (site A)
ripeds (barnacles), amphipods and tanaids (47.5%). Infaunal polychaetes (31.3%)
and bivalves (3.3%) are much less represented with respect to the other sites. The
large amount of organogenous dead remains présent in this sédiment is composed of recent and sub-fossil tests of various benthic organisms. The most conspicuous and abundant remains were the tests of the deep-water barnacles of the
genus Bathylasma (a few of them were also found alive) and mollusc gastropods
of the genus Trophon (Muricidae). Dead skeletons of solitary and colonial
madreporarians, bryozoans and tubes of serpulid polychaetes were also abundant. Such dead remains were also présent on pebbles and tests of barnacles. The
dimensions of both dead and living organisms were generally relatively small,
probably due to the prevalence of young individuals. With respect to the replicates
of site B, this site is characterised by higher variability and patchiness in the composition of living fauna.
Faunal density (Fig. 5) showed the highest mean value at site B with more than
1000 individuals m"2, followed by site C (ca. 500 individuals m’2) and site A (430
individuals m'2). These values, which are the first available for the deep sédiment
of the Ross Sea, are from one to two orders of magnitude lower than those recorded at shallow depth in other soft bottoms of the Ross Sea, such as McMurdo Sound
[18] and Terra Nova Bay [19].