340
S. Schiaparelli et al.
concept of temporal stability is valid for much of
the world oceans and over mesoscale terms, on a
short basis periodic variability appears to be
more common in certain areas of the deep-sea
than originally supposed (Tyler 1988).
Predictable and unpredictable processes may be
responsible of variations in the deep-sea environment (Tyler 1988): physical features and seasonality in vertical flux are usually of a short
time scale and predictable, while unpredictable
events may be considered turbidity currents,
sediment slides and benthic storms. The most
considerable and predictable fraction of the vertical flux is constituted by the rain of small particles derived from surface primary and secondary production (organic and inorganic particles, macrophyte detritus, faecal pellets and large
food falls of moults), while deadfall of carcasses
and river run-off are unpredictable. Seasonal
processes are mainly responsible for growth.
spawning and recruitment of deep-sea benthic
organisms (Gage and Tyler 1981; Tyler 1988).
while unpredictable events can play a relevant
role in determining small scale patchiness in
mega-, macro- and meiobenthic organism distribution and relevant abundance of scavenger
species (Dayton and Hessler 1972).
In order to evaluate deep-sea community
structure and its stability, a comparison between
present and past data sets was carried out off the
Fig. 1. Location of sampling area
Portofino Promontory (Eastern Ligurian Sea.
Mediterranean Sea), comparing data recorded in
1981 and 1996. The investigated area (between
400 and 700 m depth) is located on a very steep
continental slope, characterised by the presence
of drainage lines, river run-off from the Entella
river and strongly affected by anthropogenic
activities (fishery and dumping).
The analysis of community structure was
carried out taking into account biocoenotical
and trophic features, evidencing analogies and
discrepancies between recent and past data.
Materials and Methods
Samples were collected in April 1981 (Cattaneo
and Albertelli 1983), on board of the H/V L.P.
Marsili and in April 1996, on board of the H/V
Ammiraglio Magnaghi. in an area off the
Portofino Promontory around 44°14.2 Nand
09"08.5 E (0.5 nautical mile radius; Fig. 1).
Sampling was performed using a Van Veen
grab (0.1 m 2 ): 36 samples were collected in 1981,
ranging in depth between 428 and 760 m, while
24 were collected in 1996, between 438 and 690 m
depth.
Samples were sieved using a 1 mm mesh
sieve, preserved in 10% formaline and sorted in
the laboratory, using a stereomicroscope.
S. Schiaparelli et al.
concept of temporal stability is valid for much of
the world oceans and over mesoscale terms, on a
short basis periodic variability appears to be
more common in certain areas of the deep-sea
than originally supposed (Tyler 1988).
Predictable and unpredictable processes may be
responsible of variations in the deep-sea environment (Tyler 1988): physical features and seasonality in vertical flux are usually of a short
time scale and predictable, while unpredictable
events may be considered turbidity currents,
sediment slides and benthic storms. The most
considerable and predictable fraction of the vertical flux is constituted by the rain of small particles derived from surface primary and secondary production (organic and inorganic particles, macrophyte detritus, faecal pellets and large
food falls of moults), while deadfall of carcasses
and river run-off are unpredictable. Seasonal
processes are mainly responsible for growth.
spawning and recruitment of deep-sea benthic
organisms (Gage and Tyler 1981; Tyler 1988).
while unpredictable events can play a relevant
role in determining small scale patchiness in
mega-, macro- and meiobenthic organism distribution and relevant abundance of scavenger
species (Dayton and Hessler 1972).
In order to evaluate deep-sea community
structure and its stability, a comparison between
present and past data sets was carried out off the
Fig. 1. Location of sampling area
Portofino Promontory (Eastern Ligurian Sea.
Mediterranean Sea), comparing data recorded in
1981 and 1996. The investigated area (between
400 and 700 m depth) is located on a very steep
continental slope, characterised by the presence
of drainage lines, river run-off from the Entella
river and strongly affected by anthropogenic
activities (fishery and dumping).
The analysis of community structure was
carried out taking into account biocoenotical
and trophic features, evidencing analogies and
discrepancies between recent and past data.
Materials and Methods
Samples were collected in April 1981 (Cattaneo
and Albertelli 1983), on board of the H/V L.P.
Marsili and in April 1996, on board of the H/V
Ammiraglio Magnaghi. in an area off the
Portofino Promontory around 44°14.2 Nand
09"08.5 E (0.5 nautical mile radius; Fig. 1).
Sampling was performed using a Van Veen
grab (0.1 m 2 ): 36 samples were collected in 1981,
ranging in depth between 428 and 760 m, while
24 were collected in 1996, between 438 and 690 m
depth.
Samples were sieved using a 1 mm mesh
sieve, preserved in 10% formaline and sorted in
the laboratory, using a stereomicroscope.