332
Nutrition of Corals
photosynthesis varied within a relatively narrow scale: 20-40 llg Oz g -I h- I
in massive corals, and 30-50 llg Oz in ramose or foliose species with high
ratios of biomass to skeletal material.
The rates of photosynthesis cm- z of surface in corals ranged from 10 to
50 llg Oz h -I (Table 9.1). Sometimes it was even over 100 llg g -I (Edmunds
and Davies 1986). Calculated m- z of surface of colonies, it will be some
0.2-0.6g0 z h- 1 or 0.7-2gCm- Z day-l. The photosynthesis rates 10- 6 of
zooxanthellae cells are very stable. In different species of corals it ranges
from 10 to 15llgOzh-1 (Table 9.3). Taking their usual numbers of 2-3 x
10 6 cells g-I, the rate of photosynthesis should be 20-40 llg g-I h -I. The
rates of photosynthesis mg -I of chlorophyll a are 10-12 mg Oz or 45 mg C mg -I chI a h -I. The latter value corresponds to the assimilation
number of chlorophyll h- I . As can be seen, it is in zooxanthellae within the
same range as in phytoplankton, in which it varies between 2 to 10 mg C.
The photosynthesis rates in symbiotic octocorals, calculated g-I wet
weight, appears to be very similar to those in the ramose scleractinians
(Table 9.6): 30-lOOllgOzh-l. This reflects for them a common strategy of
disposition of the zooxanthellae in polyps by one cell layer, and the
disposition of polyps in the colony in such a way as to escape selfshadowing. Thus, in both groups of corals their photosynthetic apparatus
reached during its development optimal power by the given morphometry of
the colonies. The maximum rate of photosynthesis among the investigated
symbiotic Anthozoa, recorded in the zoantharian Zoanthus sociatus, devoid
of mineral skeleton was: 214llg0zh-1 or about 2mgOzday-1 g-I wet
weight (Tables 9.6,9.9).
The value of gross photosynthesis (PI) per day is approximately ten times
more than the values per hour of the midday period (Tables 9.1, 9.2). It has
been usually expressed in carbon units. Per gram of dry colony weight in
ramose and in foliose corals it ranges usually from 100 to 300 llg C g-l. In
some species (Meruiina, Pocillopora) it will reach even 400-500 llg. In
massive corals it is between 40-80 llg. Calculated cm -z of colony surface,
the PI values in scleractinian corals range from 50 to 300 llg C (Table 9.4),
which corresponds to 0.5-3gCm- Z day-1 (P.S. Davies 1977). An average
ratio of the active (photosynthesizing) surface area in corals to the
projective area of their colonies is between 5-8 (Dahl 1976). Thus at 100%
of cover of bottom surface coral communities could produce 325gCm- Z day-l. Actually, the percentage of cover is less and their gross
photosynthesis production ranges from 2 to 10 g C. But sometimes it could
reach 20-22 g C. Calculated by their projective area, the photosynthesis of
corals even with relatively low rates of photosynthesis, like Millepora and
Porites, was between 3.4-1O.7gCm- Z day-l (Beyer 1966). In the octocorals
of Caribbean reefs the PI values were 3.7 -6.8 g C, and in some scleractinians
from the same reefs: 2.7-1O.2gCm- Z day-l (Kanwisher and Wainwright
1967). According to Taylor (1973b), with 100% coral cover of the bottom on
the Caribbean reefs, and at the rate of their photosynthesis cm- z being
Nutrition of Corals
photosynthesis varied within a relatively narrow scale: 20-40 llg Oz g -I h- I
in massive corals, and 30-50 llg Oz in ramose or foliose species with high
ratios of biomass to skeletal material.
The rates of photosynthesis cm- z of surface in corals ranged from 10 to
50 llg Oz h -I (Table 9.1). Sometimes it was even over 100 llg g -I (Edmunds
and Davies 1986). Calculated m- z of surface of colonies, it will be some
0.2-0.6g0 z h- 1 or 0.7-2gCm- Z day-l. The photosynthesis rates 10- 6 of
zooxanthellae cells are very stable. In different species of corals it ranges
from 10 to 15llgOzh-1 (Table 9.3). Taking their usual numbers of 2-3 x
10 6 cells g-I, the rate of photosynthesis should be 20-40 llg g-I h -I. The
rates of photosynthesis mg -I of chlorophyll a are 10-12 mg Oz or 45 mg C mg -I chI a h -I. The latter value corresponds to the assimilation
number of chlorophyll h- I . As can be seen, it is in zooxanthellae within the
same range as in phytoplankton, in which it varies between 2 to 10 mg C.
The photosynthesis rates in symbiotic octocorals, calculated g-I wet
weight, appears to be very similar to those in the ramose scleractinians
(Table 9.6): 30-lOOllgOzh-l. This reflects for them a common strategy of
disposition of the zooxanthellae in polyps by one cell layer, and the
disposition of polyps in the colony in such a way as to escape selfshadowing. Thus, in both groups of corals their photosynthetic apparatus
reached during its development optimal power by the given morphometry of
the colonies. The maximum rate of photosynthesis among the investigated
symbiotic Anthozoa, recorded in the zoantharian Zoanthus sociatus, devoid
of mineral skeleton was: 214llg0zh-1 or about 2mgOzday-1 g-I wet
weight (Tables 9.6,9.9).
The value of gross photosynthesis (PI) per day is approximately ten times
more than the values per hour of the midday period (Tables 9.1, 9.2). It has
been usually expressed in carbon units. Per gram of dry colony weight in
ramose and in foliose corals it ranges usually from 100 to 300 llg C g-l. In
some species (Meruiina, Pocillopora) it will reach even 400-500 llg. In
massive corals it is between 40-80 llg. Calculated cm -z of colony surface,
the PI values in scleractinian corals range from 50 to 300 llg C (Table 9.4),
which corresponds to 0.5-3gCm- Z day-1 (P.S. Davies 1977). An average
ratio of the active (photosynthesizing) surface area in corals to the
projective area of their colonies is between 5-8 (Dahl 1976). Thus at 100%
of cover of bottom surface coral communities could produce 325gCm- Z day-l. Actually, the percentage of cover is less and their gross
photosynthesis production ranges from 2 to 10 g C. But sometimes it could
reach 20-22 g C. Calculated by their projective area, the photosynthesis of
corals even with relatively low rates of photosynthesis, like Millepora and
Porites, was between 3.4-1O.7gCm- Z day-l (Beyer 1966). In the octocorals
of Caribbean reefs the PI values were 3.7 -6.8 g C, and in some scleractinians
from the same reefs: 2.7-1O.2gCm- Z day-l (Kanwisher and Wainwright
1967). According to Taylor (1973b), with 100% coral cover of the bottom on
the Caribbean reefs, and at the rate of their photosynthesis cm- z being