Biological Factors of Formation and Erosion
25
high-latitude Abrolhos reefs off West Australia - close to SOgm- 2 day
(Johannes et al. 1983a). An average annual production of CaC03 on these
reefs was evaluated as being within 12 g m -2 which corresponded to an
annual reef growth of 2 cm. As an average, the annual production of lime in
communities of reef-flat and outer reef slope was approximately within
3-5 kgm- 2 (Smith 1973, 1983; Table 1.5). The rate of calcification, the
same as other processes of biogeochemical metabolism in reef communities,
is subjected to seasonal fluctuations (Barnes 1988).
In lagoons the rate of calcification is usually lower: 4-6 g m -2 day-I. The
carbonate material is produced there mostly by calcareous algae and
foraminifera. The annual production of CaC03 in lagoons ranges within 1 to
3 kg m -2. Its average production in various reef or atoll communities was
estimated to be within 1-7 kg CaC03 m -2 (Smith and Kinsey 1976; d.
Table 10.3). Per 1 km 2 of their area reefs are producing about 2-4 thousand
tonnes of carbonaceous material. This quantity demonstrates, that coral reef
ecosystems are extremely powerful generators of lime in marine environments. Reef biogenic carbonates thus sedimented contain besides CaC03
also many other elements and minerals, like MgC03 , Sr, C03 , Mg(NH4)P04 ,
PO~-, Fe 3 +, Cu 2 +, NiH, Zn 2 +, Pb 2 + (John 1974; Dodge et al. 1984).
Global annual carbonate production on coral reefs was evaluated to be close
to 2.5 x 10 9 tons.
Vertical linear growth rate of the reefs themselves was estimated by
geologists with the aid of radiocarbon dating of cores. Before reaching
stabilized sea level during the Holocene transgression, the rate of reef
growth ranged within 2 to 12 mm year-I. This growth rate corresponds to
the calcification rate (without taking erosion into account) of 3 to 20gm- 2
year, which was higher than the calcification rates on modern reefs that also
reached stabilized sea level (d. Table 1.5). Now it could be evaluated to be
within 1-4 m 10- 3 years (Hubbard 1985). The rate of vertical reef growth
appears to be dependent upon the level of wave stress. Under conditions of
permanent strong wave stress consolidated reef plateaus grow less fast, they
being more solid than in calm environments because the reef body in the
first case is constructed largely by slow-growing coralline algae which resist
better the surf than corals, and in the second case mostly by fast-growing
branching corals. As examples of slow-growing wave-stressed reefs the
Pacific atolls could be mentioned, and of fast-growing less-stressed reefs,
those of the Caribbean region (Adey 1978).
The consolidated reef rocks, which reef-building organisms construct on
the plateau of modern reef-flat and patch reefs, are simultaneously subjected
to intensive erosion (Highsmith 1981; Trudgill 1983). Its products, reworked
by surf into soft sediments, are transported to the reef edge and moving
down its slopes reach the bottom of the surrounding ocean. Thus they
participate in the formation of carbonate oozes on island and continental
slopes and on adjacent deep oceanic floor. The sedimentation rates in the
lagoons of the ring and barrier reefs was estimated to be within 1-
25
high-latitude Abrolhos reefs off West Australia - close to SOgm- 2 day
(Johannes et al. 1983a). An average annual production of CaC03 on these
reefs was evaluated as being within 12 g m -2 which corresponded to an
annual reef growth of 2 cm. As an average, the annual production of lime in
communities of reef-flat and outer reef slope was approximately within
3-5 kgm- 2 (Smith 1973, 1983; Table 1.5). The rate of calcification, the
same as other processes of biogeochemical metabolism in reef communities,
is subjected to seasonal fluctuations (Barnes 1988).
In lagoons the rate of calcification is usually lower: 4-6 g m -2 day-I. The
carbonate material is produced there mostly by calcareous algae and
foraminifera. The annual production of CaC03 in lagoons ranges within 1 to
3 kg m -2. Its average production in various reef or atoll communities was
estimated to be within 1-7 kg CaC03 m -2 (Smith and Kinsey 1976; d.
Table 10.3). Per 1 km 2 of their area reefs are producing about 2-4 thousand
tonnes of carbonaceous material. This quantity demonstrates, that coral reef
ecosystems are extremely powerful generators of lime in marine environments. Reef biogenic carbonates thus sedimented contain besides CaC03
also many other elements and minerals, like MgC03 , Sr, C03 , Mg(NH4)P04 ,
PO~-, Fe 3 +, Cu 2 +, NiH, Zn 2 +, Pb 2 + (John 1974; Dodge et al. 1984).
Global annual carbonate production on coral reefs was evaluated to be close
to 2.5 x 10 9 tons.
Vertical linear growth rate of the reefs themselves was estimated by
geologists with the aid of radiocarbon dating of cores. Before reaching
stabilized sea level during the Holocene transgression, the rate of reef
growth ranged within 2 to 12 mm year-I. This growth rate corresponds to
the calcification rate (without taking erosion into account) of 3 to 20gm- 2
year, which was higher than the calcification rates on modern reefs that also
reached stabilized sea level (d. Table 1.5). Now it could be evaluated to be
within 1-4 m 10- 3 years (Hubbard 1985). The rate of vertical reef growth
appears to be dependent upon the level of wave stress. Under conditions of
permanent strong wave stress consolidated reef plateaus grow less fast, they
being more solid than in calm environments because the reef body in the
first case is constructed largely by slow-growing coralline algae which resist
better the surf than corals, and in the second case mostly by fast-growing
branching corals. As examples of slow-growing wave-stressed reefs the
Pacific atolls could be mentioned, and of fast-growing less-stressed reefs,
those of the Caribbean region (Adey 1978).
The consolidated reef rocks, which reef-building organisms construct on
the plateau of modern reef-flat and patch reefs, are simultaneously subjected
to intensive erosion (Highsmith 1981; Trudgill 1983). Its products, reworked
by surf into soft sediments, are transported to the reef edge and moving
down its slopes reach the bottom of the surrounding ocean. Thus they
participate in the formation of carbonate oozes on island and continental
slopes and on adjacent deep oceanic floor. The sedimentation rates in the
lagoons of the ring and barrier reefs was estimated to be within 1-