CHAPTER 30
The Role of Sponge Bioerosion in Mediterranean Coralligenous
Accretion
C. CerranoI, G. Bavestrello Z , C.N. BianchP, B. CalcinaiI, R. Cattaneo-Vietti!) C. MorrP, and M. Sara 1
ABSTRACT
Coralligenous biocoenoses developed almost 10,000 years ago in the Mediterranean Sea, forming environments characterized by high levels of biodiversity. They are complex biogenic structures growing through the continuous overlapping of organogenic layers, between 20 and 130
m depth. The coralligenous substrate, for the concurrent presence of bio-builders (algae, serpulid worms, bryozoans, and scleractinians) and destroying elements (dionid sponges, bivalves)
is subject to dynamic evolution. Studies conducted on sections of coralligenous blocks show
that algae are the main component responsible for the building of these concretions.
Calcareous remains of benthic animals lack in mineral structures and are one ofthe most important detritus-forming elements at the bottom of vertical cliffs.
This seems to be due to the attack of dionids which selectively bore animal rather than plant
carbonates. A study on the population dynamics of some anthozoans with a calcareous skeleton has shown that about 100% of the newly settled specimens are probably removed by clionids. In this way, the substratum is cyclically renewed by the continuous boring action of clionids.
It is a sort of intermediate disturbance which controls the evolution and the structure of skiophilous zQOcoenosis, through primary space regeneration. A high specific richness. typical of
coralJigenous biocoenosis, is developed by this action. From a geological point of view, it forms
a kind of limestone, characteristic of biogenic constructions and detritic bottoms under the cliff.
Introduction
Coralligenous communities are, in the Mediterranean Sea, among the most complex and diversified assemblages living on hard-bottoms. In the
last 10,000 years, they have contributed to creating significant organogenic reef-like bioconstructions, between 20 and 100 m depth (Laborel1987;
Sartoretto et ale 1996). These structures result
from a multi-stratified accretion, made of a
macro algae and invertebrates complex, in
dynamic equilibrium due to the simultaneous
activities of builders (coralline rhodophythes,
sc1eractinians, bryozoans, serpulids) and different
disruptive agents, of which clionids and allied
sponges are the most important ones (Sara 1973).
Whenever either of these actions prevails) it
favours the accretion or the erasion of these bioconstructions.
Coralligenous biocoenoses have high biodiversity: for example, off Marseilles, they include
more than 650 species of invertebrates (Hong
1982). Sara (1973) listed one hundred sponges in
the coralligenous biocoenosis platform off the
Apulian coast. Their biomass, which can exceed
500 g dw m- 2 (Bellan-Santini 1985), is also high.
This figure is comparable to those measured in
tropical coral reefs (Sorakin 1993).
The richness and diversity of species in
coralligenous biocoenoses are partially due to
their evident substrate heterogeneity, which has
3-dimensional features. Hong (1982) underlined
the abundance of crevices and micro cavities
which, depending on their size and exposure.
host large kinds of organisms) distributed
according to light irradiance and water movement. Moreover, these cavities are subject to different rates of organic and inorganic sedimenta1 Dipartimento per 10 Studio del Territorio e delle Sue Risorse dell'Universita di Genova, Via Balbi 5, 16126 Genova, Italy
2 Istituto di Scienze del Mare dell'Universita di Ancona, Via Brecce Bianroe, 60131 Ancona, Italy
3 Istituto di Ricerca suUe Acque, ENEA Santa Teresa, P.D Box 316, 19100 La Spezia, Italy
P.M. Faranda, L. Guglielmo. G. Spezie (eda)
Mediterranean Ecosystems: Structures and Processes
© Springer-Verlag Italia 2001
The Role of Sponge Bioerosion in Mediterranean Coralligenous
Accretion
C. CerranoI, G. Bavestrello Z , C.N. BianchP, B. CalcinaiI, R. Cattaneo-Vietti!) C. MorrP, and M. Sara 1
ABSTRACT
Coralligenous biocoenoses developed almost 10,000 years ago in the Mediterranean Sea, forming environments characterized by high levels of biodiversity. They are complex biogenic structures growing through the continuous overlapping of organogenic layers, between 20 and 130
m depth. The coralligenous substrate, for the concurrent presence of bio-builders (algae, serpulid worms, bryozoans, and scleractinians) and destroying elements (dionid sponges, bivalves)
is subject to dynamic evolution. Studies conducted on sections of coralligenous blocks show
that algae are the main component responsible for the building of these concretions.
Calcareous remains of benthic animals lack in mineral structures and are one ofthe most important detritus-forming elements at the bottom of vertical cliffs.
This seems to be due to the attack of dionids which selectively bore animal rather than plant
carbonates. A study on the population dynamics of some anthozoans with a calcareous skeleton has shown that about 100% of the newly settled specimens are probably removed by clionids. In this way, the substratum is cyclically renewed by the continuous boring action of clionids.
It is a sort of intermediate disturbance which controls the evolution and the structure of skiophilous zQOcoenosis, through primary space regeneration. A high specific richness. typical of
coralJigenous biocoenosis, is developed by this action. From a geological point of view, it forms
a kind of limestone, characteristic of biogenic constructions and detritic bottoms under the cliff.
Introduction
Coralligenous communities are, in the Mediterranean Sea, among the most complex and diversified assemblages living on hard-bottoms. In the
last 10,000 years, they have contributed to creating significant organogenic reef-like bioconstructions, between 20 and 100 m depth (Laborel1987;
Sartoretto et ale 1996). These structures result
from a multi-stratified accretion, made of a
macro algae and invertebrates complex, in
dynamic equilibrium due to the simultaneous
activities of builders (coralline rhodophythes,
sc1eractinians, bryozoans, serpulids) and different
disruptive agents, of which clionids and allied
sponges are the most important ones (Sara 1973).
Whenever either of these actions prevails) it
favours the accretion or the erasion of these bioconstructions.
Coralligenous biocoenoses have high biodiversity: for example, off Marseilles, they include
more than 650 species of invertebrates (Hong
1982). Sara (1973) listed one hundred sponges in
the coralligenous biocoenosis platform off the
Apulian coast. Their biomass, which can exceed
500 g dw m- 2 (Bellan-Santini 1985), is also high.
This figure is comparable to those measured in
tropical coral reefs (Sorakin 1993).
The richness and diversity of species in
coralligenous biocoenoses are partially due to
their evident substrate heterogeneity, which has
3-dimensional features. Hong (1982) underlined
the abundance of crevices and micro cavities
which, depending on their size and exposure.
host large kinds of organisms) distributed
according to light irradiance and water movement. Moreover, these cavities are subject to different rates of organic and inorganic sedimenta1 Dipartimento per 10 Studio del Territorio e delle Sue Risorse dell'Universita di Genova, Via Balbi 5, 16126 Genova, Italy
2 Istituto di Scienze del Mare dell'Universita di Ancona, Via Brecce Bianroe, 60131 Ancona, Italy
3 Istituto di Ricerca suUe Acque, ENEA Santa Teresa, P.D Box 316, 19100 La Spezia, Italy
P.M. Faranda, L. Guglielmo. G. Spezie (eda)
Mediterranean Ecosystems: Structures and Processes
© Springer-Verlag Italia 2001