Heterotrophic Feeding of Corals
355
A e ,%
7,7
72
9
6'
3
"
/J 0
u,¥
0,0
a' 1,2
K"
0
0, /J,7
0,1
tJ, 1,7
1J,2D Kd
Fig. 9.6. Dependence of the rates of feeding in corals on DOM (1) and on
bacterioplankton (2); A feeding rate, % of total energy demand; Kb and Kd concentration
of food - bacterioplankton (mgl- 1 ) and DOM (mgCl- 1 ); band d ranges of their ambient
concentrations in waters over the reef
bacterioplankton concentrations in waters over the reef, corals should, on
an average, compensate by means of feeding on bacterioplankton about
10-15% of their total energy demand (Kb) (Fig. 9.6).
The first estimations of coral's feeding on DOM, employing labeled
organic compounds (Stephens 1962; Goreau et al. 1971) were rather
qualitative. They did not answer the question about the possibility of corals
acquiring significant amounts of food at ambient concentrations of
assimilable fractions of labeled dissolved organic matter in coral-reef waters.
The results of our quantitative estimations of corals feeding on DOM based
on the measurements of its specific radioactivity in the experiments, are
given in Table 9.17. They proved that the rate of feeding of most reef corals
tested with DOM is commensurable with the rates of their feeding on
bacterioplankton. At a concentration of assimilable DOM of 1 mg C 1- 1 , the
rate of its assimilation by corals was 20-60~gCg-1day-1, or 20-40% of
respiration losses. The real content of labile DOM in reef waters was
evaluated to be within 0.2-0.5 mg C. At these cocentrations, in accordance
with the curve (Fig. 9.6), corals should compensate 12-18% of their total
energy demand (A/MG). The assimilation of dissolved amino acids by corals
was recently demonstrated by Titlyanov et al. (1988b); and by Drew-Ferrier
(1991).
Summarizing the data on the quantitative aspects of feeding of
scleractinian corals obtained at the Heron Island reefs, it could be concluded
that at the ambient concentration of available food they, on an average,
could compose their energy balance as follows: 70% of the needed energy is
355
A e ,%
7,7
72
9
6'
3
"
/J 0
u,¥
0,0
a' 1,2
K"
0
0, /J,7
0,1
tJ, 1,7
1J,2D Kd
Fig. 9.6. Dependence of the rates of feeding in corals on DOM (1) and on
bacterioplankton (2); A feeding rate, % of total energy demand; Kb and Kd concentration
of food - bacterioplankton (mgl- 1 ) and DOM (mgCl- 1 ); band d ranges of their ambient
concentrations in waters over the reef
bacterioplankton concentrations in waters over the reef, corals should, on
an average, compensate by means of feeding on bacterioplankton about
10-15% of their total energy demand (Kb) (Fig. 9.6).
The first estimations of coral's feeding on DOM, employing labeled
organic compounds (Stephens 1962; Goreau et al. 1971) were rather
qualitative. They did not answer the question about the possibility of corals
acquiring significant amounts of food at ambient concentrations of
assimilable fractions of labeled dissolved organic matter in coral-reef waters.
The results of our quantitative estimations of corals feeding on DOM based
on the measurements of its specific radioactivity in the experiments, are
given in Table 9.17. They proved that the rate of feeding of most reef corals
tested with DOM is commensurable with the rates of their feeding on
bacterioplankton. At a concentration of assimilable DOM of 1 mg C 1- 1 , the
rate of its assimilation by corals was 20-60~gCg-1day-1, or 20-40% of
respiration losses. The real content of labile DOM in reef waters was
evaluated to be within 0.2-0.5 mg C. At these cocentrations, in accordance
with the curve (Fig. 9.6), corals should compensate 12-18% of their total
energy demand (A/MG). The assimilation of dissolved amino acids by corals
was recently demonstrated by Titlyanov et al. (1988b); and by Drew-Ferrier
(1991).
Summarizing the data on the quantitative aspects of feeding of
scleractinian corals obtained at the Heron Island reefs, it could be concluded
that at the ambient concentration of available food they, on an average,
could compose their energy balance as follows: 70% of the needed energy is