CHAPTER 47
Change and Diversity: the Mediterranean Deep Corals
from the Miocene to the Present
C.Corselli
ABSTRACT
During the last eighteen million years plate tectonics have deeply modified the physiography
and the morphology of the Mediterranean Sea, with changes in basin oceanography, chemistry
and biology. The presence and the depth of the western sill made it a semi-closed basin, heavily conditioned by the climate in its oceanographic features. In addition during the Pleistocene,
the global climatic deterioration affected the circulation of the superficial and deep waters of
the Mediterranean and the composition of its biota. The reconstruction of the chemical and
physical characteristics of the deep waters of the Mediterranean sea, by the corals, shows the
progressive isolation of the basin during the last 12 million years. Associated to this isolation a
progressive decrease in the specific diversity in the deep coral fauna occurs, only partly arrested
during the glacial phases.
Introduction
According to Picard (1985) a macro-ecosystem
changes in terms of geologic time and a mesoecosystem, instead, has a temporal length from
some millennia to a few centuries. Among the
climatic factors the temperature in particular
influences the duration of the macro-ecosystems
and in the deep sea ecosystems the temperatures
of some oceans have not substantially changed
in the last 30-40 millions of years. The stable
temperature that has characterized the bathyal
and abyssal depths. in the considered time, has
certainly influenced the evolution of the organisms relatively inducing a high biological diversity with a low density. The auto ecology of the
still living coral species allows to reconstruct the
past environments, while the specific diversity
testifies to changes that have occurred in the
physical and chemical parameters of a marine
basin. Nevertheless the age of a biological
species could be extremely variable from ten
thousand to some million years and the biologists have not always taken into account the age
of a still living species. Frequently they have preferred to institute a new species without verifying the possibility that the living organism corresponds to a fossil taxon, instituted for long
time. An insufficient documentation (lack or
loss of the original types) or few accurate morphological descriptions has often represented
the alibi for such a choice. The paleontological
record of some coral deep taxa documents a
long temporal duration, that, in some cases, can
also reach some million years. During the last
eighteen million years plate tectonics has deeply
modified the physiography and morphology of
the Mediterranean Sea, with changes in basin
oceanography, chemistry and biology. Here, as
in the other semi-closed sea basins, the temperature of the bottom has undergone. in the same
temporal interval, a series of fluctuations that
have deeply influenced the bathyal and abyssal
fauna and particularly the coral species. In this
paper are illustrated three case histories of the
deep coral assemblages of the Mediterranean
Sea during the Late Miocene, Pliocene-Early
Pleistocene, Late Pleistocene-Recent; such
assemblages testify the dramatic changes undergone by the basin.
Dipartimento dl Scienze Geologiche e Geotecnologie, Universita degli Srodl di Milano-Bicocca, Piazza della Scienza 4,20126
Milano, Italy
P.M. Faranda, L Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems, Structures and Processes
© Springer-Verlag Italm 2001
Change and Diversity: the Mediterranean Deep Corals
from the Miocene to the Present
C.Corselli
ABSTRACT
During the last eighteen million years plate tectonics have deeply modified the physiography
and the morphology of the Mediterranean Sea, with changes in basin oceanography, chemistry
and biology. The presence and the depth of the western sill made it a semi-closed basin, heavily conditioned by the climate in its oceanographic features. In addition during the Pleistocene,
the global climatic deterioration affected the circulation of the superficial and deep waters of
the Mediterranean and the composition of its biota. The reconstruction of the chemical and
physical characteristics of the deep waters of the Mediterranean sea, by the corals, shows the
progressive isolation of the basin during the last 12 million years. Associated to this isolation a
progressive decrease in the specific diversity in the deep coral fauna occurs, only partly arrested
during the glacial phases.
Introduction
According to Picard (1985) a macro-ecosystem
changes in terms of geologic time and a mesoecosystem, instead, has a temporal length from
some millennia to a few centuries. Among the
climatic factors the temperature in particular
influences the duration of the macro-ecosystems
and in the deep sea ecosystems the temperatures
of some oceans have not substantially changed
in the last 30-40 millions of years. The stable
temperature that has characterized the bathyal
and abyssal depths. in the considered time, has
certainly influenced the evolution of the organisms relatively inducing a high biological diversity with a low density. The auto ecology of the
still living coral species allows to reconstruct the
past environments, while the specific diversity
testifies to changes that have occurred in the
physical and chemical parameters of a marine
basin. Nevertheless the age of a biological
species could be extremely variable from ten
thousand to some million years and the biologists have not always taken into account the age
of a still living species. Frequently they have preferred to institute a new species without verifying the possibility that the living organism corresponds to a fossil taxon, instituted for long
time. An insufficient documentation (lack or
loss of the original types) or few accurate morphological descriptions has often represented
the alibi for such a choice. The paleontological
record of some coral deep taxa documents a
long temporal duration, that, in some cases, can
also reach some million years. During the last
eighteen million years plate tectonics has deeply
modified the physiography and morphology of
the Mediterranean Sea, with changes in basin
oceanography, chemistry and biology. Here, as
in the other semi-closed sea basins, the temperature of the bottom has undergone. in the same
temporal interval, a series of fluctuations that
have deeply influenced the bathyal and abyssal
fauna and particularly the coral species. In this
paper are illustrated three case histories of the
deep coral assemblages of the Mediterranean
Sea during the Late Miocene, Pliocene-Early
Pleistocene, Late Pleistocene-Recent; such
assemblages testify the dramatic changes undergone by the basin.
Dipartimento dl Scienze Geologiche e Geotecnologie, Universita degli Srodl di Milano-Bicocca, Piazza della Scienza 4,20126
Milano, Italy
P.M. Faranda, L Guglielmo, G. Spezie (eds)
Mediterranean Ecosystems, Structures and Processes
© Springer-Verlag Italm 2001