368
Nutrition of Corals
with 70-75%, which corresponds to direct measurements of CZAR by
Titlyanov et al. (1985). From this point of view the energy balance
calculated for the coral Porites and shown in Table 9.22 seems to be more
realistic.
The specific growth rate of zooxanthellae, expressed as Gz/B coefficient
per day was evaluated with 0.01-0.04, and their generation time with 40-70
days. The specific growth rates of polyps were found to be much less:
0.002-0.004 day-lor 0.7-1.5 year- I (Wilkerson et al. 1983; Muscatine et
al. 1984, 1985; Edmunds and Davies 1986). Thus the rate of growth of
zooxanthellae exceeds by much that of polyps, and so the excess of
zooxanthellae should be building up. But polyps can regulate their number
in their tissues by partial digestion or by expelling them (Fitt and Trench
1980; Colley and Trench 1985).
We have evaluated the probable specific growth rates in common corals
using the formula: G/B = (Mt • K2)/[Bp . (1 - K2)], where Bp is the biomass
of polyps and K2 the efficiency coefficients of the use of assimilated food for
growth, which in most sessile animal is close to 0.3. In different coral species
the G/B coefficients ranged from 0.006 to 0.02 day-l (Sorokin 1984a). Lewis
(1981) has obtained the specific growth rate in the community of hermatypic
corals with close to 0.005 day-t, and 1.8-2.0 year-I. Such small energy
expenditures in corals for their growth are easily provided for by
translocation and heterotrophic nutrition. Thus, their growth rate should not
be limited by the energy supply, but mostly by the rate of calcification and
by the limited growth rate of the lime skeleton of their colonies.
Nutrition of Corals
with 70-75%, which corresponds to direct measurements of CZAR by
Titlyanov et al. (1985). From this point of view the energy balance
calculated for the coral Porites and shown in Table 9.22 seems to be more
realistic.
The specific growth rate of zooxanthellae, expressed as Gz/B coefficient
per day was evaluated with 0.01-0.04, and their generation time with 40-70
days. The specific growth rates of polyps were found to be much less:
0.002-0.004 day-lor 0.7-1.5 year- I (Wilkerson et al. 1983; Muscatine et
al. 1984, 1985; Edmunds and Davies 1986). Thus the rate of growth of
zooxanthellae exceeds by much that of polyps, and so the excess of
zooxanthellae should be building up. But polyps can regulate their number
in their tissues by partial digestion or by expelling them (Fitt and Trench
1980; Colley and Trench 1985).
We have evaluated the probable specific growth rates in common corals
using the formula: G/B = (Mt • K2)/[Bp . (1 - K2)], where Bp is the biomass
of polyps and K2 the efficiency coefficients of the use of assimilated food for
growth, which in most sessile animal is close to 0.3. In different coral species
the G/B coefficients ranged from 0.006 to 0.02 day-l (Sorokin 1984a). Lewis
(1981) has obtained the specific growth rate in the community of hermatypic
corals with close to 0.005 day-t, and 1.8-2.0 year-I. Such small energy
expenditures in corals for their growth are easily provided for by
translocation and heterotrophic nutrition. Thus, their growth rate should not
be limited by the energy supply, but mostly by the rate of calcification and
by the limited growth rate of the lime skeleton of their colonies.