results were highly contradictory, because of the
organism paucity of each sampling station. The
analysis of discriminating species through Rmode analysis is reported in Table 3.
Discussion and Conclusions
Comparing data regarding the composition of
the bathyal macrobenthic assemblages living
between 400 and 700 m depth off the Portofino
Promontory (Ligurian Sea), relevant variations
between 1981 and 1996 are evident.
No differences arose regarding biomass,
density, species number and diversity, but a significant change occurred in the relationships
among the trophic groups, with an increment of
carnivores and scavengers in despite of depositfeeders.
The lack of previous long-term data on the
structure and dynamics of these deep-sea communities makes it difficult to assess whether
these differences are really true or eventually
only mirror their diversity due to biocoenoses
overlapping (Cattaneo-Vietti 1991) or patchiness, as evidenced in other deep-sea communities (Hessler and Sanders, 1967; Jumars 1975).
This heterogeneity and structural complexity may be the natural result of different stochastic processes such as localised downward organic fluxes (from POM to large carcasses). cropper
(sensu Dayton and Hessler 1972) andlor tubebuilder presence (Gray 1974; Jumars 1975,1976),
allowing coexistence of various microsuccessional stages through contemporaneous disequi1ibria (Grassle and Sanders 1973).
In the case of real variations, questions arise
about which were the main responsible events
that affected the stability of benthic communities
and influenced the dynamic nature of finegrained sediments. Are they stochastic, biologically mediated or anthropogenic?
Major changes have been stressed in the
uppermost investigated area (400-500 m), suggesting a littoral derived disturbance, probably
linked to different and synergic factors. The study
area is located dose to the Riviera di Levante
canyon, and it is affected by high density flowing
down currents transporting unstable sediments
sliding down the submarine slope (Fanucci et al.
1979; Corradi et al. 1980). Moreover these bottoms are influenced by the outflows of the Entella
river (Piccazzo 1986) and by its floods.
Variability in a Bathyal Community
345
Besides these natural influences, the area is
affected by an intensive trawling activity (Massi et
al. 1994), mainly linked to the red shrimp fishing
(Relini and Orsi Relini 1987). It is reasonable to
suppose that the continuous disturbance of the
fishing gears causes a significant reworking of the
sediment and difficulties for the bottom-stabilising organisms. Among these, Funiculina quadrangolaris and Isidella elongata for epifauna (ReliniOrsi 1973; Relini et al. 1986), and different tubebuilding polychaetes. for endofauna. The continuous fishing activity has caused quali- quantitative
changes in the commercial catches (Relini-Orsi
1973; Relini et al. 1986) and an anomalous
increase of large organic debris which favours the
scavengers (Cattaneo-Vietti et aL 1993).
Besides this permanent impact, it is possible
to take into account the authorised dumping of
harbour muds that has occurred in the last
decades which could have changed the superficial texture of the sediments up to 700 m depth.
A complex of factors favours in this area an
environmental instability which influences the
community structure, preventing the establishment of sediment-stabilising species (tubebuilders, burrow dwellers), whose presence plays
an important biological role controlling and
maintaining diversity (Rhoads and Young 1970;
Young and Rhoads 1971).
In the deep sea, these studies have a significant importance both in the evaluation of the
long-term changes andlor of anthropogenic
impact, since the only analysis of routine descriptive parameters (density, biomass, species richness and numerical dominance) are not exhaustive. as external factors could radically change the
trophic pathways in these food-limited environments and consequently the species composition.
References
Bernstein BB, Meador IF (1979) Temporal persistence ofbiological patch structure in an abyssal benthic community. Mar
BioI 51: 179-183
Bray JR, Curtis JT (1957) An ordination of the upland forest
communities of Southern Wisconsin. Ecol Monogr 27: 325349
Cabioch L, Dauvin JC,Mora Bermudez], Rodriguez Babio C (1980)
Effets de la maree noire de "Amoco Cadiz" sur Ie benthos sublittoral de la Bretagne. Helgo Meeresunters 33: 192-208
Carpine C (1970) &:ologie de l'etage bathyal dans la Mediterranee
·occidentale. Mem lnst Oceanogr Monaco 2
Cattaneo M, Albertelli G. (1983) Macrobenthos dei fundi batiali
liguri. Atti V Congr AIOL: 251-260
Cattaneo-Vietti R (1991) Bathymetric distribution of soft-bottom
organism paucity of each sampling station. The
analysis of discriminating species through Rmode analysis is reported in Table 3.
Discussion and Conclusions
Comparing data regarding the composition of
the bathyal macrobenthic assemblages living
between 400 and 700 m depth off the Portofino
Promontory (Ligurian Sea), relevant variations
between 1981 and 1996 are evident.
No differences arose regarding biomass,
density, species number and diversity, but a significant change occurred in the relationships
among the trophic groups, with an increment of
carnivores and scavengers in despite of depositfeeders.
The lack of previous long-term data on the
structure and dynamics of these deep-sea communities makes it difficult to assess whether
these differences are really true or eventually
only mirror their diversity due to biocoenoses
overlapping (Cattaneo-Vietti 1991) or patchiness, as evidenced in other deep-sea communities (Hessler and Sanders, 1967; Jumars 1975).
This heterogeneity and structural complexity may be the natural result of different stochastic processes such as localised downward organic fluxes (from POM to large carcasses). cropper
(sensu Dayton and Hessler 1972) andlor tubebuilder presence (Gray 1974; Jumars 1975,1976),
allowing coexistence of various microsuccessional stages through contemporaneous disequi1ibria (Grassle and Sanders 1973).
In the case of real variations, questions arise
about which were the main responsible events
that affected the stability of benthic communities
and influenced the dynamic nature of finegrained sediments. Are they stochastic, biologically mediated or anthropogenic?
Major changes have been stressed in the
uppermost investigated area (400-500 m), suggesting a littoral derived disturbance, probably
linked to different and synergic factors. The study
area is located dose to the Riviera di Levante
canyon, and it is affected by high density flowing
down currents transporting unstable sediments
sliding down the submarine slope (Fanucci et al.
1979; Corradi et al. 1980). Moreover these bottoms are influenced by the outflows of the Entella
river (Piccazzo 1986) and by its floods.
Variability in a Bathyal Community
345
Besides these natural influences, the area is
affected by an intensive trawling activity (Massi et
al. 1994), mainly linked to the red shrimp fishing
(Relini and Orsi Relini 1987). It is reasonable to
suppose that the continuous disturbance of the
fishing gears causes a significant reworking of the
sediment and difficulties for the bottom-stabilising organisms. Among these, Funiculina quadrangolaris and Isidella elongata for epifauna (ReliniOrsi 1973; Relini et al. 1986), and different tubebuilding polychaetes. for endofauna. The continuous fishing activity has caused quali- quantitative
changes in the commercial catches (Relini-Orsi
1973; Relini et al. 1986) and an anomalous
increase of large organic debris which favours the
scavengers (Cattaneo-Vietti et aL 1993).
Besides this permanent impact, it is possible
to take into account the authorised dumping of
harbour muds that has occurred in the last
decades which could have changed the superficial texture of the sediments up to 700 m depth.
A complex of factors favours in this area an
environmental instability which influences the
community structure, preventing the establishment of sediment-stabilising species (tubebuilders, burrow dwellers), whose presence plays
an important biological role controlling and
maintaining diversity (Rhoads and Young 1970;
Young and Rhoads 1971).
In the deep sea, these studies have a significant importance both in the evaluation of the
long-term changes andlor of anthropogenic
impact, since the only analysis of routine descriptive parameters (density, biomass, species richness and numerical dominance) are not exhaustive. as external factors could radically change the
trophic pathways in these food-limited environments and consequently the species composition.
References
Bernstein BB, Meador IF (1979) Temporal persistence ofbiological patch structure in an abyssal benthic community. Mar
BioI 51: 179-183
Bray JR, Curtis JT (1957) An ordination of the upland forest
communities of Southern Wisconsin. Ecol Monogr 27: 325349
Cabioch L, Dauvin JC,Mora Bermudez], Rodriguez Babio C (1980)
Effets de la maree noire de "Amoco Cadiz" sur Ie benthos sublittoral de la Bretagne. Helgo Meeresunters 33: 192-208
Carpine C (1970) &:ologie de l'etage bathyal dans la Mediterranee
·occidentale. Mem lnst Oceanogr Monaco 2
Cattaneo M, Albertelli G. (1983) Macrobenthos dei fundi batiali
liguri. Atti V Congr AIOL: 251-260
Cattaneo-Vietti R (1991) Bathymetric distribution of soft-bottom