284
Communities of Corals in Reef Ecosystems
has an increased number of large nematocysts (Hartog 1977). Also, these
sweeper tentacles increase their number in polyps situated at the side of the
coral approaching its competitor. The same was observed in polyps of corals
that were kept in aquarium together with their potential competitors, e.g.,
with corals ranking below them in the "scale of agressivity". Some corals,
like Goniopora, for example, may extend their polyps as far as 10-15 cm,
and so could kill their competitors at a significant distance. In the Atlantic
corals a kind of hierarchy - the "scale of aggression" - was discovered (Lang
1974; Cope 1981). The most aggressive of them belong to the families
Mussidae, Meandrinidae and Faviidae. Lang (1973) denied the aggressive
relationships between corals of the same species, while Bothwell (1984)
questioned this statement. According to Lang (1973), this hierarchy in the
coral community of Jamaican reefs, starting with the most aggressive
species, appears as follows: Mussa angulata ~ Scolymia lacera ~ Isophyllia
sinuosa ~ Mycetophillia ferox ~ Meandrina meandrites ~ Mycetophillia
danaana ~ Scolymia cubensis ~ Isophyllastrea rigida ~ Montastrea
annularis ~ Diploria labirinthiformis ~ D. strigosa ~ D. clivosa ~
Montastrea cavernosa ~ Manicina areolata ~ Acropora palmata ~ A.
cervicornis ~ Eusmilia fastigata ~ Agaricia sp. ~ Helioseris cucullata ~
Siderastrea ~ Porites ~ Madracis ~ Stephanocoenia. On the reefs off
Bermuda this hierarchy seems to be a little different: the most aggressive
corals there are Montastrea annularis, Diploria labyrinthiformis and D.
strigosa. In communities of the GBR this hierarchy within a group of the
main families of corals appears as follows Mussidae ~ Faviidae ~
Acroporidae ~ Pocilloporidae ~ Poritidae (Bothwell 1984).
In some reef regions the structure of the coral communities was subjected
to the influence of the Acanthaster plaques, which was caused by a definite
selectivity evinced by this predator in relation to its prey (Goreau et al.
1972; Glynn 1976; Done 1985). Sometimes corals may escape the attacks of
the predator, e.g. when they are well armed with the powerful nematocysts,
like the hydrocoral Millepora, the octocoral Heliopora (Lewis 1989), and
corals with massive round colonies, onto whose surface the asteroids cannot
fasten their bodies, like old colonies of the coral Pocillopora, which are
defended by their symbiotic crabs (Glynn 1981) or like corals defended by
territorial fish, the Pomacentrids. The structure of a coral community after
an attack by Acanthaster changes drastically. Its species diversity increases
with the simultaneous decrease in the percentage of bottom surface covered
by corals (Fig. 7.8).
Corallovorous fish like scarids, box fish and balistids damage corals, but
simultaneously further their vegetative propagation by crushing. the branches
of ramose corals to pieces, which then may start new colonies (Randall
1974; Tunnicliffe 1981; Highsmith 1982). Being specialized with respect to
which species of corals they eat and also as to their age and size,
corallovorous fish significantly influence the structure of coral communities
(Grassle 1973). The grazing impact on some preferred by fish corals, such as
Communities of Corals in Reef Ecosystems
has an increased number of large nematocysts (Hartog 1977). Also, these
sweeper tentacles increase their number in polyps situated at the side of the
coral approaching its competitor. The same was observed in polyps of corals
that were kept in aquarium together with their potential competitors, e.g.,
with corals ranking below them in the "scale of agressivity". Some corals,
like Goniopora, for example, may extend their polyps as far as 10-15 cm,
and so could kill their competitors at a significant distance. In the Atlantic
corals a kind of hierarchy - the "scale of aggression" - was discovered (Lang
1974; Cope 1981). The most aggressive of them belong to the families
Mussidae, Meandrinidae and Faviidae. Lang (1973) denied the aggressive
relationships between corals of the same species, while Bothwell (1984)
questioned this statement. According to Lang (1973), this hierarchy in the
coral community of Jamaican reefs, starting with the most aggressive
species, appears as follows: Mussa angulata ~ Scolymia lacera ~ Isophyllia
sinuosa ~ Mycetophillia ferox ~ Meandrina meandrites ~ Mycetophillia
danaana ~ Scolymia cubensis ~ Isophyllastrea rigida ~ Montastrea
annularis ~ Diploria labirinthiformis ~ D. strigosa ~ D. clivosa ~
Montastrea cavernosa ~ Manicina areolata ~ Acropora palmata ~ A.
cervicornis ~ Eusmilia fastigata ~ Agaricia sp. ~ Helioseris cucullata ~
Siderastrea ~ Porites ~ Madracis ~ Stephanocoenia. On the reefs off
Bermuda this hierarchy seems to be a little different: the most aggressive
corals there are Montastrea annularis, Diploria labyrinthiformis and D.
strigosa. In communities of the GBR this hierarchy within a group of the
main families of corals appears as follows Mussidae ~ Faviidae ~
Acroporidae ~ Pocilloporidae ~ Poritidae (Bothwell 1984).
In some reef regions the structure of the coral communities was subjected
to the influence of the Acanthaster plaques, which was caused by a definite
selectivity evinced by this predator in relation to its prey (Goreau et al.
1972; Glynn 1976; Done 1985). Sometimes corals may escape the attacks of
the predator, e.g. when they are well armed with the powerful nematocysts,
like the hydrocoral Millepora, the octocoral Heliopora (Lewis 1989), and
corals with massive round colonies, onto whose surface the asteroids cannot
fasten their bodies, like old colonies of the coral Pocillopora, which are
defended by their symbiotic crabs (Glynn 1981) or like corals defended by
territorial fish, the Pomacentrids. The structure of a coral community after
an attack by Acanthaster changes drastically. Its species diversity increases
with the simultaneous decrease in the percentage of bottom surface covered
by corals (Fig. 7.8).
Corallovorous fish like scarids, box fish and balistids damage corals, but
simultaneously further their vegetative propagation by crushing. the branches
of ramose corals to pieces, which then may start new colonies (Randall
1974; Tunnicliffe 1981; Highsmith 1982). Being specialized with respect to
which species of corals they eat and also as to their age and size,
corallovorous fish significantly influence the structure of coral communities
(Grassle 1973). The grazing impact on some preferred by fish corals, such as