18
Reef Lime Constructions
bottom of the surrounding sea, thus composing a significant part of the lime
component of carbonate oceanic sediments. The rocky lime reef
constructions represent an important geomorphological element of the sea
floor in tropical regions.
The basic mechanism of formation of consolidated reef rocks, either in
modern coral reefs or in ancient reefs constructed by other organisms, is the
same (Goreau and Goreau 1973; Hubbard 1985). On the shallow bottom of
warm seas large sessile animals, which have external calcareous or chitinphosphorite skeletons, build up the lime framework of the reef, which is
then filled with friable carbonaceous material composed of rubble, coral
sand, spicules, crumbs of coralline crusts, etc. This material is then
consolidated during the processes of its lithification and dolomitization
based upon the recrystallization of CaC02 (Marshall 1983). Finally, the solid
reef rocky base is gradually constructed, which resists wave stress and
composes the substrate for subsequent growth of sessile fauna (Land and
Goreau 1970).
The main framework builders on Holocene reefs in the Pacific on their
windward side were massive, cribose or corymbose corals, like Goniopora,
Goniastrea, Platygyra, Porites, Pociliopora, Symphillia. On their leeward
side, among the frameworkers the ramose coral was dominating of the
genera Acropora, Pocillopora, Miliepora (Hopley et al. 1978; Davies and
Marshall 1979). On the Atlantic reefs, the basic frameworkers are two
species of ramose acroporid corals: A. palmata and A. Cervicornis, which
have large and firm branches (Macintyre et al. 1977; Adey 1978). On the
reefs of Indian ocean (Reunion Island) the ramose corals from the genera
Acropora, Pocillopora and Montipora, together with massive poritides, were
recorded even in columns from the windward reef (Montaggini 1977). At
the fore-reef zone, where coral growth is inhibited by definiency of light, the
sclerospongia became a significant element of reef framework (Hartman
1977).
The ability to extract calcium carbonate from sea water and to deposit it
either as calcite or aragonite in the skeletal structures is possessed by
numerous reef algae and animals. This function of calcification is especially
developed in photo-autotrophs - in plants such as calcareous macrophytes
and those in symbiosis with algae animals, such as symbiotic foraminifera,
corals and tridacnid bivalves. The function of calcification is possessed also
by various asymbiotic animals like ahermatypic (asymbiotic) corals,
sedentary polychaetes, bryozoans, tunicates, echinoderms, and asymbiotic
forams. But in any case the main producers of lime material on reefs and the
main reef builders remain the photoautotrophs (Kiihlmann 1988a).
The calcification in animal symbiotic photoautotrophs results in the
formation of crystals of lime in the form of aragonite. This process occurs in
special calcyoblast cells of the epidermis (Vandermeuler and Watabe 1974).
It is definitely coupled with photosynthesis of their algal symbionts the
zooxanthellae (cf. Sect. 8.3). In experiments, the calcification rate in corals
Reef Lime Constructions
bottom of the surrounding sea, thus composing a significant part of the lime
component of carbonate oceanic sediments. The rocky lime reef
constructions represent an important geomorphological element of the sea
floor in tropical regions.
The basic mechanism of formation of consolidated reef rocks, either in
modern coral reefs or in ancient reefs constructed by other organisms, is the
same (Goreau and Goreau 1973; Hubbard 1985). On the shallow bottom of
warm seas large sessile animals, which have external calcareous or chitinphosphorite skeletons, build up the lime framework of the reef, which is
then filled with friable carbonaceous material composed of rubble, coral
sand, spicules, crumbs of coralline crusts, etc. This material is then
consolidated during the processes of its lithification and dolomitization
based upon the recrystallization of CaC02 (Marshall 1983). Finally, the solid
reef rocky base is gradually constructed, which resists wave stress and
composes the substrate for subsequent growth of sessile fauna (Land and
Goreau 1970).
The main framework builders on Holocene reefs in the Pacific on their
windward side were massive, cribose or corymbose corals, like Goniopora,
Goniastrea, Platygyra, Porites, Pociliopora, Symphillia. On their leeward
side, among the frameworkers the ramose coral was dominating of the
genera Acropora, Pocillopora, Miliepora (Hopley et al. 1978; Davies and
Marshall 1979). On the Atlantic reefs, the basic frameworkers are two
species of ramose acroporid corals: A. palmata and A. Cervicornis, which
have large and firm branches (Macintyre et al. 1977; Adey 1978). On the
reefs of Indian ocean (Reunion Island) the ramose corals from the genera
Acropora, Pocillopora and Montipora, together with massive poritides, were
recorded even in columns from the windward reef (Montaggini 1977). At
the fore-reef zone, where coral growth is inhibited by definiency of light, the
sclerospongia became a significant element of reef framework (Hartman
1977).
The ability to extract calcium carbonate from sea water and to deposit it
either as calcite or aragonite in the skeletal structures is possessed by
numerous reef algae and animals. This function of calcification is especially
developed in photo-autotrophs - in plants such as calcareous macrophytes
and those in symbiosis with algae animals, such as symbiotic foraminifera,
corals and tridacnid bivalves. The function of calcification is possessed also
by various asymbiotic animals like ahermatypic (asymbiotic) corals,
sedentary polychaetes, bryozoans, tunicates, echinoderms, and asymbiotic
forams. But in any case the main producers of lime material on reefs and the
main reef builders remain the photoautotrophs (Kiihlmann 1988a).
The calcification in animal symbiotic photoautotrophs results in the
formation of crystals of lime in the form of aragonite. This process occurs in
special calcyoblast cells of the epidermis (Vandermeuler and Watabe 1974).
It is definitely coupled with photosynthesis of their algal symbionts the
zooxanthellae (cf. Sect. 8.3). In experiments, the calcification rate in corals