Biological Factors of Formation and Erosion
17
reefs with submerged flats or with depressions in their middle or rear
parts abundant coral communities develop on the surface, consisting of
ecomorphs which resist physical stress (Grassle 1973; Stoddart 1969).
Ramose corals often form there micro atolls (Scoffin and Stoddart 1978).
A significant part of the submerged flats is covered by macrophytes, sea
grasses and ramose Corallinaceae (Milliman 1969).
d) Re - Rear or inner reef flat zone, depth 1-4m. This zone is
stretching along the backward part of the reef flat or along the inner reef
slopes facing the lagoon. The zone is structured by patch reefs - round
planar lime hillocks 2-20 m large - which are constructed by corals and
coralline algae in calm reef shallows on the sandy bottom. Their surface
is often exposed during ebb-tides.
e) Ls - Inner lagoonal reef slope zone, depth 2-20m. It is represented
by steep sandy or rubble slopes from the inner reef edge at the "rear"
zone towards the lagoon.
f) L - Zone of lagoon, depth 5-40 m. This is the depression fringed by
the reef. Its depth is largely dependent upon the phase of reef evolution:
the older is the reef, and shallower is its lagoon. In shallow lagoons over
50% of its sandy bottom is usually covered by patch reefs and by thickets
of ramose corals. In deep lagoons at depths of 20-40 m knolls or
pinnacles rise. Some of them reach the sea surface (Milliman 1969). In
lagoon shallows microatolls are forming, and the bottom is covered by
macrophytes and seagrasses. Lagoons of large ring and barrier reefs often
occupy more than half of the total of their areas.
g) Lr - Leeward reef zone, depth 0-2 m. This zone is represented
usually by stripes of patch reefs, micro-atolls, and by ridges of rubble and
dead corals. Islands and sand cays often form there.
Some researchers in their studies of reef geomorphology make a distinction
between specific biotopes (Pichon 1978) and typical landscapes
(Preobrazhensky 1986), according to what seemed to be useful for their
survey descriptions.
1.2 Biological Factors of Formation and Erosion
The sedimentation and accretion of biogenic carbonates is one of the most
important functions of coral reef ecosystems. It is one of the most remarkable global biogeochemical processes. Even at its stationary phase
of growth in conditions of stabilized sea level, the reef biota produces
4-5kgm- 2 of CaC02 per year, while at the phase of active reef growth
during the Holocene transgression this value attained 20 kg m -2. Annual
production of CaC02 at modern reefs approximates 2.5 x 10 9 1. A large part
of crumbly carbonate material thus produced is transferred from reefs to the
17
reefs with submerged flats or with depressions in their middle or rear
parts abundant coral communities develop on the surface, consisting of
ecomorphs which resist physical stress (Grassle 1973; Stoddart 1969).
Ramose corals often form there micro atolls (Scoffin and Stoddart 1978).
A significant part of the submerged flats is covered by macrophytes, sea
grasses and ramose Corallinaceae (Milliman 1969).
d) Re - Rear or inner reef flat zone, depth 1-4m. This zone is
stretching along the backward part of the reef flat or along the inner reef
slopes facing the lagoon. The zone is structured by patch reefs - round
planar lime hillocks 2-20 m large - which are constructed by corals and
coralline algae in calm reef shallows on the sandy bottom. Their surface
is often exposed during ebb-tides.
e) Ls - Inner lagoonal reef slope zone, depth 2-20m. It is represented
by steep sandy or rubble slopes from the inner reef edge at the "rear"
zone towards the lagoon.
f) L - Zone of lagoon, depth 5-40 m. This is the depression fringed by
the reef. Its depth is largely dependent upon the phase of reef evolution:
the older is the reef, and shallower is its lagoon. In shallow lagoons over
50% of its sandy bottom is usually covered by patch reefs and by thickets
of ramose corals. In deep lagoons at depths of 20-40 m knolls or
pinnacles rise. Some of them reach the sea surface (Milliman 1969). In
lagoon shallows microatolls are forming, and the bottom is covered by
macrophytes and seagrasses. Lagoons of large ring and barrier reefs often
occupy more than half of the total of their areas.
g) Lr - Leeward reef zone, depth 0-2 m. This zone is represented
usually by stripes of patch reefs, micro-atolls, and by ridges of rubble and
dead corals. Islands and sand cays often form there.
Some researchers in their studies of reef geomorphology make a distinction
between specific biotopes (Pichon 1978) and typical landscapes
(Preobrazhensky 1986), according to what seemed to be useful for their
survey descriptions.
1.2 Biological Factors of Formation and Erosion
The sedimentation and accretion of biogenic carbonates is one of the most
important functions of coral reef ecosystems. It is one of the most remarkable global biogeochemical processes. Even at its stationary phase
of growth in conditions of stabilized sea level, the reef biota produces
4-5kgm- 2 of CaC02 per year, while at the phase of active reef growth
during the Holocene transgression this value attained 20 kg m -2. Annual
production of CaC02 at modern reefs approximates 2.5 x 10 9 1. A large part
of crumbly carbonate material thus produced is transferred from reefs to the