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Morphology and Ecological Physiology of Corals
higher rate of growth by the same rate of calcification and so overgrow the
massive corals and better escape siltation (Shinn 1963; Connell 1973;
Vosburgh 1982; Bottier 1980). Another preference of ramose corals could
be seen in their better ability to catch zooplankton, which has been proved
experimentally (cf. Sect. 9.2). In fact, corals hunt most successfully at dawn
and dusk, when the demersal zooplankters rise or return to the bottom,
Also, they feed on zooplankton, which is driven by the current laterally. It
seems quite obvious that by the experimentally proved equal ability of large
and small polyps to catch mesozooplankton, their preference will be for
polyps of ramose species, properly distributed in space. Ramose corals have
also one more important preference - their increased ability for vegetative
multiplication by fragmentation, which greatly improves their ability to
compete for the hard substrate with other sessile fauna (Highsmith 1982).
Their ability, widespread among corals, to form adaptive ecomorphs, was
mentioned above. For example, some massive corals, like Montastrea, in
poorly illuminated deep reef zones form folioses, or crustose colonies
(Barnes 1973; Dustan 1975; Graus and Macintyre 1976; Preobrazhensky and
Ivanov 1982). The flattened colony is formed by the module corallites which
grow only at the edges of young coral, while in corals that live in normal
light, growth proceeds over their whole surface. The flat form of a colony is
optimal for a poorly illuminated environment. Corals under these conditions
have a deficiency of energetic resources for growth and direct the available
resources only to the narrow zone of growth. It provides them with the
ability to attain a speed of growth sufficient to escape siltation and to
compete with other corals for space, moreover the flat form of a colony
enables them also to construct the necessary light-collecting surface with a
minimal expenditure of resources (Dustan 1975). In the upper reef zone the
massive round or columnar form should be preferable. It endures better the
waves, grazing, overgrowth and siltation, compared with the flat or foliose
form. The ramose corals in deep biotopes also form flattened colonies, in
which most branches grow laterally, being perpendicular to the direction of
the light stream (Titlyanov et al. 1988c; Titlyanov and Latypov, 1991). Thus,
their energy resources are used to support growth only in one plane, which
maintains its normal speed at a low general rate of calcification, inhibited in
deep reef zones by a deficiency of such light energy penetrating there. The
lateral-form colony also avoids the self-shadowing of branches which is
important in light-deficient environments.
The formation of versatile ecomorphs in colonies living in upper reef
zones is connected with their adaptive phenotypic variability under the
influence of various kinds of physical strees and grazing (see Sect. 7.3). The
conditions of hydrodynamics influence also the form of the colonies of
gorgonacean octocorals. For example, in calm waters the colonies of
Eunicella stricta look like so many separate whips, while in the surf zones
they are bush-like, and on slopes visited by permanent currents fan-like, like
many other gorgonians living there (Theodor 1963). The planes of these fan
Morphology and Ecological Physiology of Corals
higher rate of growth by the same rate of calcification and so overgrow the
massive corals and better escape siltation (Shinn 1963; Connell 1973;
Vosburgh 1982; Bottier 1980). Another preference of ramose corals could
be seen in their better ability to catch zooplankton, which has been proved
experimentally (cf. Sect. 9.2). In fact, corals hunt most successfully at dawn
and dusk, when the demersal zooplankters rise or return to the bottom,
Also, they feed on zooplankton, which is driven by the current laterally. It
seems quite obvious that by the experimentally proved equal ability of large
and small polyps to catch mesozooplankton, their preference will be for
polyps of ramose species, properly distributed in space. Ramose corals have
also one more important preference - their increased ability for vegetative
multiplication by fragmentation, which greatly improves their ability to
compete for the hard substrate with other sessile fauna (Highsmith 1982).
Their ability, widespread among corals, to form adaptive ecomorphs, was
mentioned above. For example, some massive corals, like Montastrea, in
poorly illuminated deep reef zones form folioses, or crustose colonies
(Barnes 1973; Dustan 1975; Graus and Macintyre 1976; Preobrazhensky and
Ivanov 1982). The flattened colony is formed by the module corallites which
grow only at the edges of young coral, while in corals that live in normal
light, growth proceeds over their whole surface. The flat form of a colony is
optimal for a poorly illuminated environment. Corals under these conditions
have a deficiency of energetic resources for growth and direct the available
resources only to the narrow zone of growth. It provides them with the
ability to attain a speed of growth sufficient to escape siltation and to
compete with other corals for space, moreover the flat form of a colony
enables them also to construct the necessary light-collecting surface with a
minimal expenditure of resources (Dustan 1975). In the upper reef zone the
massive round or columnar form should be preferable. It endures better the
waves, grazing, overgrowth and siltation, compared with the flat or foliose
form. The ramose corals in deep biotopes also form flattened colonies, in
which most branches grow laterally, being perpendicular to the direction of
the light stream (Titlyanov et al. 1988c; Titlyanov and Latypov, 1991). Thus,
their energy resources are used to support growth only in one plane, which
maintains its normal speed at a low general rate of calcification, inhibited in
deep reef zones by a deficiency of such light energy penetrating there. The
lateral-form colony also avoids the self-shadowing of branches which is
important in light-deficient environments.
The formation of versatile ecomorphs in colonies living in upper reef
zones is connected with their adaptive phenotypic variability under the
influence of various kinds of physical strees and grazing (see Sect. 7.3). The
conditions of hydrodynamics influence also the form of the colonies of
gorgonacean octocorals. For example, in calm waters the colonies of
Eunicella stricta look like so many separate whips, while in the surf zones
they are bush-like, and on slopes visited by permanent currents fan-like, like
many other gorgonians living there (Theodor 1963). The planes of these fan