CHAPTER 36
Deep-sea (250-1,550 m) Benthic Thanatocoenoses
from the Southern Tyrrhenian Sea
I. Di Geronimo, A. Rosso, R. La Perna, and R. Sanfilippo
ABSTRACT
Bathyal benthic thanatocoenoses from 28 stations in the Southern Tyrrhenian Sea are studied,
focusing on molluscs, bryozoans and serpulids. On the basis of faunal affinities, sampled stations
were grouped into three bathymetrical belts: "A" (248-505 m), "BII (696-1,096 m) and "(" (1,139',536 m).Major faunal changes occurred between 500 and 600 m depths (i.e. between belts A and
B), due to changes in the dominant molluscs (mainly Benthonella ten ella, Ennucula corbu/oides,
Ledella messanensis, Yoldiella micrometrica and Katadesmia cuneata), bryozoans (e.g. Tubulipora
sp. 1 and Setosella foliml and serpulids (e.g. Filogranula stellato and Filograna sp. 1), which were
absent in belt A, and increased in abundance in the deepest belt (el. Faunas from stations below
500-600 m may define the typical Mediterranean deep bathyal assemblages. Differences between
Pleistocene and Recent bathyal Mediterranean benthos are discussed. We hypothesise that the
latter is "residual': i.e. composed mainly by species that endured changes that occurred from the
psycrospheric Plio-Pleistocene to the warm-homothermic Recent conditions.
Introduction
The Mediterranean Sea is a threshold-basin whose
peculiar hydrology is reflected in a poor deep-sea
biota, in terms of both species richness and density (or biomass; Fredj and Laubier 1985). These features, coupled with a high spatial heterogeneity
(Harmelin and d'Hondt 1993), represent problems
in studying the deep Mediterranean communities.
Dead assemblages (i.e. thanatocoenoses) from
deep-sea bottoms are generally rather abundant
and diversified. The origin of such thanatocoenoses cannot be referred to Atlantic
meroplankton, without reaching fertile conditions
in adult populations settled into the WesternMediterranean. Although larval inflow is likely,
and "hard parts" of organism remains of Atlantic
species (dating back to the Last Glacial) are present (Di Geronimo and Li Gioi 1981; Bouchet and
Taviani 1989; Rosso 1990), most deep-sea thanatocoenoses should be referred to Recent and biogeographically autochthonous communities.
Studies on the deep Mediterranean macrobenthos are mainly taxonomic, often included
in research focused on North Atlantic faunas.
Few data are available on the deep-sea assemblages and the distribution pattern of species.
Peres and Picard (1964), Carpine (1970). Di
Geronimo (1974) and Janssen (1989), mainly
focusing on molluscs, have attempted to recognise depth-related assemblages.
In the present investigation, three benthic
groups (molluscs, bryozoans and serpulids) were
considered. Thanatocoenoses come from 25 cm
deep cores from soft bottoms with high sedimentation rates. According to literature data
from the westernmost Mediterranean (Loubere
1982) these thanatocoenoses can be assumed as
being only two-three thousand years old and
then wholly Holocene in age.
The present investigation focuses on composition and depth range of bathyal thanatocoenoses from the Southern Tyrrhenian Sea, discussing them within the evolution model of the
deep Mediterranean benthos.
Dipartimento di Scienze Geologiche, Sezione di Oceanologia e Paleoecologia, Universita di Catania, Corso Italia 55, 95129
Catania. Italy
EM. Faranda, L. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Processes
@ Springer-Verlag ltalia 2001
Deep-sea (250-1,550 m) Benthic Thanatocoenoses
from the Southern Tyrrhenian Sea
I. Di Geronimo, A. Rosso, R. La Perna, and R. Sanfilippo
ABSTRACT
Bathyal benthic thanatocoenoses from 28 stations in the Southern Tyrrhenian Sea are studied,
focusing on molluscs, bryozoans and serpulids. On the basis of faunal affinities, sampled stations
were grouped into three bathymetrical belts: "A" (248-505 m), "BII (696-1,096 m) and "(" (1,139',536 m).Major faunal changes occurred between 500 and 600 m depths (i.e. between belts A and
B), due to changes in the dominant molluscs (mainly Benthonella ten ella, Ennucula corbu/oides,
Ledella messanensis, Yoldiella micrometrica and Katadesmia cuneata), bryozoans (e.g. Tubulipora
sp. 1 and Setosella foliml and serpulids (e.g. Filogranula stellato and Filograna sp. 1), which were
absent in belt A, and increased in abundance in the deepest belt (el. Faunas from stations below
500-600 m may define the typical Mediterranean deep bathyal assemblages. Differences between
Pleistocene and Recent bathyal Mediterranean benthos are discussed. We hypothesise that the
latter is "residual': i.e. composed mainly by species that endured changes that occurred from the
psycrospheric Plio-Pleistocene to the warm-homothermic Recent conditions.
Introduction
The Mediterranean Sea is a threshold-basin whose
peculiar hydrology is reflected in a poor deep-sea
biota, in terms of both species richness and density (or biomass; Fredj and Laubier 1985). These features, coupled with a high spatial heterogeneity
(Harmelin and d'Hondt 1993), represent problems
in studying the deep Mediterranean communities.
Dead assemblages (i.e. thanatocoenoses) from
deep-sea bottoms are generally rather abundant
and diversified. The origin of such thanatocoenoses cannot be referred to Atlantic
meroplankton, without reaching fertile conditions
in adult populations settled into the WesternMediterranean. Although larval inflow is likely,
and "hard parts" of organism remains of Atlantic
species (dating back to the Last Glacial) are present (Di Geronimo and Li Gioi 1981; Bouchet and
Taviani 1989; Rosso 1990), most deep-sea thanatocoenoses should be referred to Recent and biogeographically autochthonous communities.
Studies on the deep Mediterranean macrobenthos are mainly taxonomic, often included
in research focused on North Atlantic faunas.
Few data are available on the deep-sea assemblages and the distribution pattern of species.
Peres and Picard (1964), Carpine (1970). Di
Geronimo (1974) and Janssen (1989), mainly
focusing on molluscs, have attempted to recognise depth-related assemblages.
In the present investigation, three benthic
groups (molluscs, bryozoans and serpulids) were
considered. Thanatocoenoses come from 25 cm
deep cores from soft bottoms with high sedimentation rates. According to literature data
from the westernmost Mediterranean (Loubere
1982) these thanatocoenoses can be assumed as
being only two-three thousand years old and
then wholly Holocene in age.
The present investigation focuses on composition and depth range of bathyal thanatocoenoses from the Southern Tyrrhenian Sea, discussing them within the evolution model of the
deep Mediterranean benthos.
Dipartimento di Scienze Geologiche, Sezione di Oceanologia e Paleoecologia, Universita di Catania, Corso Italia 55, 95129
Catania. Italy
EM. Faranda, L. Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems: Structures and Processes
@ Springer-Verlag ltalia 2001