244
S. Cocito and S. Sgorbini
morphology with sub-circular perimeter. medium sized colonies developed a more enlarged
shape with elliptic perimeter. and the largest
colonies, after collapse of the central upper part
and the periphery of the base of attachment,
approximated a bowl perched on top of a narrow
pedestal.
The vulnerability of a colony to water current impact is also a function of its age. strength
of skeleton and tenacity of attachment (Denny et
al. 1985). Consequently. changes in colony mass
and morphology may be associated with changes
in stability, hydrodynamic properties and susceptibility to dislodgement. In fact, in the deeper
station, the three largest colonies. which exhibited the above mentioned morphology, and consequently a greater susceptibility to mechanical
dislodgement, were no longer present two years
after the storm.
The natural more routine disturbances, such
as sedimentation and epibiosis, showed a longerterm effect to which Pentapora fascialis' colonies
responded at the beginning with partial mortality and afterwards with total mortality.
Acknowledgements. We thank F. Ferdeghini (La Spezia) and
G.M.R. Manzella (La Spezia) for suggestions. Research on
Pentapora fascialis falls within the scope of the project
'Marine Biodiversity' (MURST) of the Marine Environment
Research Centre of ENEA.
References
Airoldi L, Fabiano M, Cinelli F (1996) Sediment deposition and
movement over a turf assemblage in a shallow rocky coastal
area of the Ligurian Sea. Mar Ecol Prog Ser 133: 241-251
Buss LW (1979) Bryozoan overgrowth interactions - the interdependence of competition for space and food. Nature 281:
475-477
Cheetham AH (1986) Branching, biomechanics and bryozoan
evolution. Proc R Soc London 228. pp 151-171
Cheetham AH, ThoIlIllen E (1981) Functional morphology of
arborescent animals: strength and design of cheUostome
bryozoan skeletons. Paleobiology 7: 355-383
Cocito S, Ferdeghini F (1998) Marcatura con colorante ed etichettatura: due metodi per misurare 1a crescita in briozoi calcificati. In: Piccazzo M (ed) Atti XII Congr Assoc Ital Oceanol
Limnol AIOL 2, pp 351-358
Gocito S, Sgorbini S, Bianchi eN (1997) Zonation of a suspensionfeeder assemblage on a temperate rocky shoal: the influence
of water current and bottom topography. In: Hawkins LE,
Hutchinson S (eds) The response of marine organisms to
their Environments. Univ Southampton. UK, pp 183-192
Cocito S, Ferdeghini F. Sgorbini S (1998a) Pentapora fascialis
(Pallas) [Cheilostomata: Ascophoral colonisation of one
sublittoral rocky site after sea-storm in the northwestern
Mediterranean. In: Baden S. Pihl L. Rosemberg R.
Stromberg. fO, Svane I, Tiselius P (eds) Recruitment, colonisation, and physical-chemical forcing in marine biological
SysteIlIll. Kluwer Acad Publ, Belgium, pp 59-66
Cocito S. Sgorbini S. Bianchi CN (1998b) Aspects of the biology of
the bryozoan Pentapora foscialis in the north-western
Mediterranean. Mar BioI 131: 73-82
Connell TH, Keough MJ (1985) Disturbance and patchy dynamics
of subtidal marine animals on hard substrata. In: Pickett
STA, White PS (eds) The ecology of natural disturbance and
patch dynamics. Academic Press, London, pp 125-151
Denny MY, Daniel TR. Koehl MAR (1985) Mechanical limits to
size in wave-swept organisIlIll. Ecol Monogr 55: 69-102
Done TJ (1992) Effects of tropical cyclone waves on ecological
and geomorphological structures on the Great Barrier Reef.
Cont Shelf Res 12 (7/8): 859-872
Done TJ. Potts DC (1992) Influence of habitat and natural disturbance on contributions of massive Porites corals to reef
communities. Mar BioI 114: 479-493
Frechette M. Aitken AE. Page L (1992) Interdependence of food
and space limitation in benthic suspension feeder: consequence for self-thinning relationship. Mar Ecol Prog Ser 83:
55-62
Gautier YV (1962) Recherchtls ecologiques sur les bryozoaires
chilostomes en Mlhliterrantle occidentale. Rec Trav Stu Mar
Endoume 38: 163-168
Harvell CD, Caswell H, Simpson P (1990) Density effects in a colonial monoculture: experimental studies with a marine bryozoan (Membranipora membranacea L.). Oecologia 95: 595598
Hayward PJ. Ryland JS (1979) British Ascophoran bryozoans.
Kermack DM, Barnes RSK (eds) Synopses of the British
Fauna. Academic Press, London, pp 1-312
Hughes TP (1990) Recruitment limitation, mortality, and population regulation in open system: a case study. Ecology 7 (1):
12-20
Jackson IBC (1979) Morphological strategies of sessile animals.
In: Larwood G, Rosen BR (eds) Biology and systematics of
colonial organisms. Academic Press, London. pp 499-555
McKinney FK. Jackson JBC (1989) Erect growth: problems of
breakage and flow. In: McKinney FK, Jackson TBC (eds)
Bryozoan evolution. Univ Chicago Press, Chicago, pp 167189
Pickett STA, White PS (1985) Patch dynamics: a synthesis. In:
Pickett STA, White PS (eds) The ecology of natural disturbance and patch dynamics. Academic Press, Orlando, pp
371-394
Rogers CS (1993) Hurricanes and coral reefs: the intermediate
hypothesis revisited. Coral Reefs 12: 127-137
Sala E, Garrabou J, Zabala M (1996) Effects of diver frequentation
on Mediterranean sublittoral populations of the bryozoan
Pentapora fascialis. Mar BioI 126: 451-459
Sgorbini S, Codto S, Bianchi CN (1996) Underwater photography
as a tool to monitor the population dynamics of a clonal
organism. In: Albertelli G, De Maio A, Piccazzo M (eds) Atti
XI Congr Assnc Ital Oceanol Limn.ol AIOL, Genova, pp 819826
Stebbing ARD (1971) Growth of PlUJtra foliacea (Bryozoa). Mar
BioI 9: 267-273
Woodley JD, Chornesky EA, Clifford PA, Jackson IRC, Kaufman 15
et al (1981) Hurricane Allen's impact on Jamaican corals.
Science 214 (4522): 749-755
S. Cocito and S. Sgorbini
morphology with sub-circular perimeter. medium sized colonies developed a more enlarged
shape with elliptic perimeter. and the largest
colonies, after collapse of the central upper part
and the periphery of the base of attachment,
approximated a bowl perched on top of a narrow
pedestal.
The vulnerability of a colony to water current impact is also a function of its age. strength
of skeleton and tenacity of attachment (Denny et
al. 1985). Consequently. changes in colony mass
and morphology may be associated with changes
in stability, hydrodynamic properties and susceptibility to dislodgement. In fact, in the deeper
station, the three largest colonies. which exhibited the above mentioned morphology, and consequently a greater susceptibility to mechanical
dislodgement, were no longer present two years
after the storm.
The natural more routine disturbances, such
as sedimentation and epibiosis, showed a longerterm effect to which Pentapora fascialis' colonies
responded at the beginning with partial mortality and afterwards with total mortality.
Acknowledgements. We thank F. Ferdeghini (La Spezia) and
G.M.R. Manzella (La Spezia) for suggestions. Research on
Pentapora fascialis falls within the scope of the project
'Marine Biodiversity' (MURST) of the Marine Environment
Research Centre of ENEA.
References
Airoldi L, Fabiano M, Cinelli F (1996) Sediment deposition and
movement over a turf assemblage in a shallow rocky coastal
area of the Ligurian Sea. Mar Ecol Prog Ser 133: 241-251
Buss LW (1979) Bryozoan overgrowth interactions - the interdependence of competition for space and food. Nature 281:
475-477
Cheetham AH (1986) Branching, biomechanics and bryozoan
evolution. Proc R Soc London 228. pp 151-171
Cheetham AH, ThoIlIllen E (1981) Functional morphology of
arborescent animals: strength and design of cheUostome
bryozoan skeletons. Paleobiology 7: 355-383
Cocito S, Ferdeghini F (1998) Marcatura con colorante ed etichettatura: due metodi per misurare 1a crescita in briozoi calcificati. In: Piccazzo M (ed) Atti XII Congr Assoc Ital Oceanol
Limnol AIOL 2, pp 351-358
Gocito S, Sgorbini S, Bianchi eN (1997) Zonation of a suspensionfeeder assemblage on a temperate rocky shoal: the influence
of water current and bottom topography. In: Hawkins LE,
Hutchinson S (eds) The response of marine organisms to
their Environments. Univ Southampton. UK, pp 183-192
Cocito S, Ferdeghini F. Sgorbini S (1998a) Pentapora fascialis
(Pallas) [Cheilostomata: Ascophoral colonisation of one
sublittoral rocky site after sea-storm in the northwestern
Mediterranean. In: Baden S. Pihl L. Rosemberg R.
Stromberg. fO, Svane I, Tiselius P (eds) Recruitment, colonisation, and physical-chemical forcing in marine biological
SysteIlIll. Kluwer Acad Publ, Belgium, pp 59-66
Cocito S. Sgorbini S. Bianchi CN (1998b) Aspects of the biology of
the bryozoan Pentapora foscialis in the north-western
Mediterranean. Mar BioI 131: 73-82
Connell TH, Keough MJ (1985) Disturbance and patchy dynamics
of subtidal marine animals on hard substrata. In: Pickett
STA, White PS (eds) The ecology of natural disturbance and
patch dynamics. Academic Press, London, pp 125-151
Denny MY, Daniel TR. Koehl MAR (1985) Mechanical limits to
size in wave-swept organisIlIll. Ecol Monogr 55: 69-102
Done TJ (1992) Effects of tropical cyclone waves on ecological
and geomorphological structures on the Great Barrier Reef.
Cont Shelf Res 12 (7/8): 859-872
Done TJ. Potts DC (1992) Influence of habitat and natural disturbance on contributions of massive Porites corals to reef
communities. Mar BioI 114: 479-493
Frechette M. Aitken AE. Page L (1992) Interdependence of food
and space limitation in benthic suspension feeder: consequence for self-thinning relationship. Mar Ecol Prog Ser 83:
55-62
Gautier YV (1962) Recherchtls ecologiques sur les bryozoaires
chilostomes en Mlhliterrantle occidentale. Rec Trav Stu Mar
Endoume 38: 163-168
Harvell CD, Caswell H, Simpson P (1990) Density effects in a colonial monoculture: experimental studies with a marine bryozoan (Membranipora membranacea L.). Oecologia 95: 595598
Hayward PJ. Ryland JS (1979) British Ascophoran bryozoans.
Kermack DM, Barnes RSK (eds) Synopses of the British
Fauna. Academic Press, London, pp 1-312
Hughes TP (1990) Recruitment limitation, mortality, and population regulation in open system: a case study. Ecology 7 (1):
12-20
Jackson IBC (1979) Morphological strategies of sessile animals.
In: Larwood G, Rosen BR (eds) Biology and systematics of
colonial organisms. Academic Press, London. pp 499-555
McKinney FK. Jackson JBC (1989) Erect growth: problems of
breakage and flow. In: McKinney FK, Jackson TBC (eds)
Bryozoan evolution. Univ Chicago Press, Chicago, pp 167189
Pickett STA, White PS (1985) Patch dynamics: a synthesis. In:
Pickett STA, White PS (eds) The ecology of natural disturbance and patch dynamics. Academic Press, Orlando, pp
371-394
Rogers CS (1993) Hurricanes and coral reefs: the intermediate
hypothesis revisited. Coral Reefs 12: 127-137
Sala E, Garrabou J, Zabala M (1996) Effects of diver frequentation
on Mediterranean sublittoral populations of the bryozoan
Pentapora fascialis. Mar BioI 126: 451-459
Sgorbini S, Codto S, Bianchi CN (1996) Underwater photography
as a tool to monitor the population dynamics of a clonal
organism. In: Albertelli G, De Maio A, Piccazzo M (eds) Atti
XI Congr Assnc Ital Oceanol Limn.ol AIOL, Genova, pp 819826
Stebbing ARD (1971) Growth of PlUJtra foliacea (Bryozoa). Mar
BioI 9: 267-273
Woodley JD, Chornesky EA, Clifford PA, Jackson IRC, Kaufman 15
et al (1981) Hurricane Allen's impact on Jamaican corals.
Science 214 (4522): 749-755