264
Communities of Corals in Reef Ecosystems
columnar colonies, when living in calm and poorly illuminated deeper zones
acquire the tendency to form fiat or incrusting colonies (cf. Sect. 7.3).
The total number of species and the index of species diversity also vary in
various zones. The lowest numbers of species were usually recorded on reef
shallows and during the ebbs exposed parts of reef fiats. In zones on reefs of
the Indo-Pacific the number of coral species varied between 10-30, and on
reefs of the Atlantic between 3-5. Most often the numbers of species were
maximal in zones of buttress and apper fore-reef, and on outer reef slope at
depths of 1O-20m with illumination of 10-20% of PARS (penetrated
surface photosynthetically active radiation). In these zones on reefs of the
Indo-Pacific the number of species in the communities was within 40-100,
and on the West Atlantic reefs within 10-30 (Sheppard 1980; Ross and
Hodson 1981; Sy et al. 1981; cf. Figs. 7.5, 7.6). Below 30m the number of
species in coral communities gradually decreases down to 10-40 species in
the Indo-Pacific, and to 5-10 in the Atlantic. Sometimes the maximum
number of coral species could be observed also on submerged fiats of Pacific
reefs - up to 100-120 (Wells 1954). A high species diversity was also
recorded even in the wind-stressed biotopes of windward reef fiats. As
examples, the Heron Island reef, GBR (Bothwell 1984), and the reefs off
Mindoro Island, Philippines, could be mentioned (Ross and Hodson 1981).
The indexes of species diversity H' (Shannon-Winer) in coral communities
are extremely high and reach their maxima (3-4) in biotopes of the outer
slope, as also in diverse communities of coral reef fish (Table 7.4). But the
corals are not likewise specialized in relation to their trophic sources.
Moreover, they are apparently similar in this respect (cf. Sect. 9.2.1). So
this cause of high diversity, which seems to be true for fish does not apply in
corals. This could be seen in the high degree of repetition of catastrophic
events to which coral reef communities are subjected. These events are
N
oil
ZtJ
!
11
811C1(Wa~d pent of
?eel :lfad
Oute~
uel
stope
!O ~
zo ",,'
.YO ~
~
/ltJ
.fO
Fig. 7.S. Total number of coral species (N) and species diversity index (H') in different
zones of the Apo reef, Philippines; upper curve profile of bottom. (Data by Ross and
Hodson 1981)
Communities of Corals in Reef Ecosystems
columnar colonies, when living in calm and poorly illuminated deeper zones
acquire the tendency to form fiat or incrusting colonies (cf. Sect. 7.3).
The total number of species and the index of species diversity also vary in
various zones. The lowest numbers of species were usually recorded on reef
shallows and during the ebbs exposed parts of reef fiats. In zones on reefs of
the Indo-Pacific the number of coral species varied between 10-30, and on
reefs of the Atlantic between 3-5. Most often the numbers of species were
maximal in zones of buttress and apper fore-reef, and on outer reef slope at
depths of 1O-20m with illumination of 10-20% of PARS (penetrated
surface photosynthetically active radiation). In these zones on reefs of the
Indo-Pacific the number of species in the communities was within 40-100,
and on the West Atlantic reefs within 10-30 (Sheppard 1980; Ross and
Hodson 1981; Sy et al. 1981; cf. Figs. 7.5, 7.6). Below 30m the number of
species in coral communities gradually decreases down to 10-40 species in
the Indo-Pacific, and to 5-10 in the Atlantic. Sometimes the maximum
number of coral species could be observed also on submerged fiats of Pacific
reefs - up to 100-120 (Wells 1954). A high species diversity was also
recorded even in the wind-stressed biotopes of windward reef fiats. As
examples, the Heron Island reef, GBR (Bothwell 1984), and the reefs off
Mindoro Island, Philippines, could be mentioned (Ross and Hodson 1981).
The indexes of species diversity H' (Shannon-Winer) in coral communities
are extremely high and reach their maxima (3-4) in biotopes of the outer
slope, as also in diverse communities of coral reef fish (Table 7.4). But the
corals are not likewise specialized in relation to their trophic sources.
Moreover, they are apparently similar in this respect (cf. Sect. 9.2.1). So
this cause of high diversity, which seems to be true for fish does not apply in
corals. This could be seen in the high degree of repetition of catastrophic
events to which coral reef communities are subjected. These events are
N
oil
ZtJ
!
11
811C1(Wa~d pent of
?eel :lfad
Oute~
uel
stope
!O ~
zo ",,'
.YO ~
~
/ltJ
.fO
Fig. 7.S. Total number of coral species (N) and species diversity index (H') in different
zones of the Apo reef, Philippines; upper curve profile of bottom. (Data by Ross and
Hodson 1981)