Biological Factors of Formation and Erosion
19
Table 1.2. Rate of calcification (Rc) and its light dependence (after Goreau and Goreau
1960b)
Organisms
Algae
Corals
Taxa
Galaxaura sp.
Halimeda opunta
Lithothamnion sp.
Acropora cervicornis (apical branches)
Acropora cervicornis (lateral branches)
Porites furcata
Millepora complanata
In the light
143.0
8.9
2.4
3.3
0.9
0.28
0.26
In the dark
92.0
6.4
2.1
0.4
0.1
0.08
0.14
increased by an average of about one order of values in the light as
compared with that in the dark (Goreau 1963; Barnes and Taylor 1973;
Chalker 1983; Huston 1985; cf. Table 1.2). In some corals it increased in the
light up to 40 times, but in the hydrocoral Millepora calcification appears to
be less sensitive to light. The coupling of calcification with photosynthesis in
scleractinian corals was also proved in experiments with a specific inhibitor
of the latter - DCMU - which inhibited in them also the calcification
(Chalker 1983). Concerning the mechanisms of this coupling, one thing
seems to be obvious: the pumping out of CO) ions (and probably other acid
products, like the lower organic acids) by Zooxanthellae from the zones of
calcification in the polyp's calcyoblasts (Muscatine 1971). They also consume
NHt and PO) ions which inhibit crystallization of CaC03 (Goreau 1963;
Yonge 1973; Grossland and Barnes 1974). The zooxanthellae produce also
organic polymers of chitine type which accomplish the function of nuclei for
the aragonite crystals (Yonge 1973; Johnston 1979). Being the generators of
chemically bound energy within the polyp's cells, they also provide the
energy supply for the process of Ca 2 + -ions transport through the membranes
of polyp's cells (Barnes and Taylor 1973). Scleractinian hermatypic corals
deposit CaC03 in state of aragonite crystals. Besides, in corals colonies the
calcite crystals could be also found; they appear there as a result of
secondary recrystallization which proceeds actively in holes made in them by
borers (Macintyre and Towe 1976).
The rate of calcification (Rc) could be measured as the weight or as the
volume accretion rates of colonies, by estimation of Ca2+ -ions consumption
from water, via observations of COz-balance in water by means of recording
pH changes in time or by using ratiotracers' 45Ca and 14C (Goreau 1963;
Drew 1973; Stoddart and Johannes 1978; Jokiel et a1. 1978; Barnes and
Crossland 1978; Barnes and Deveraux 1984). The in situ measurements of
this value showed that its diurnal variation in general coincided with the
diurnal curve of the coral's gross photosynthesis (cf. Sect. 8.4; Chalker
1983). The light dependence curves of the coral's calcification appeared to
19
Table 1.2. Rate of calcification (Rc) and its light dependence (after Goreau and Goreau
1960b)
Organisms
Algae
Corals
Taxa
Galaxaura sp.
Halimeda opunta
Lithothamnion sp.
Acropora cervicornis (apical branches)
Acropora cervicornis (lateral branches)
Porites furcata
Millepora complanata
In the light
143.0
8.9
2.4
3.3
0.9
0.28
0.26
In the dark
92.0
6.4
2.1
0.4
0.1
0.08
0.14
increased by an average of about one order of values in the light as
compared with that in the dark (Goreau 1963; Barnes and Taylor 1973;
Chalker 1983; Huston 1985; cf. Table 1.2). In some corals it increased in the
light up to 40 times, but in the hydrocoral Millepora calcification appears to
be less sensitive to light. The coupling of calcification with photosynthesis in
scleractinian corals was also proved in experiments with a specific inhibitor
of the latter - DCMU - which inhibited in them also the calcification
(Chalker 1983). Concerning the mechanisms of this coupling, one thing
seems to be obvious: the pumping out of CO) ions (and probably other acid
products, like the lower organic acids) by Zooxanthellae from the zones of
calcification in the polyp's calcyoblasts (Muscatine 1971). They also consume
NHt and PO) ions which inhibit crystallization of CaC03 (Goreau 1963;
Yonge 1973; Grossland and Barnes 1974). The zooxanthellae produce also
organic polymers of chitine type which accomplish the function of nuclei for
the aragonite crystals (Yonge 1973; Johnston 1979). Being the generators of
chemically bound energy within the polyp's cells, they also provide the
energy supply for the process of Ca 2 + -ions transport through the membranes
of polyp's cells (Barnes and Taylor 1973). Scleractinian hermatypic corals
deposit CaC03 in state of aragonite crystals. Besides, in corals colonies the
calcite crystals could be also found; they appear there as a result of
secondary recrystallization which proceeds actively in holes made in them by
borers (Macintyre and Towe 1976).
The rate of calcification (Rc) could be measured as the weight or as the
volume accretion rates of colonies, by estimation of Ca2+ -ions consumption
from water, via observations of COz-balance in water by means of recording
pH changes in time or by using ratiotracers' 45Ca and 14C (Goreau 1963;
Drew 1973; Stoddart and Johannes 1978; Jokiel et a1. 1978; Barnes and
Crossland 1978; Barnes and Deveraux 1984). The in situ measurements of
this value showed that its diurnal variation in general coincided with the
diurnal curve of the coral's gross photosynthesis (cf. Sect. 8.4; Chalker
1983). The light dependence curves of the coral's calcification appeared to