148
5. VERIFYING MODELS
different environments. In stony corals, skeleton architecture shows the history of the colony growth. X-rayed photographs of the slab of the colony
section (see for example Fig. 2.34) provide us information on the growth process, such as the growth rate and the angle of corallite growth. The details of
the skeleton band will be described in Sect. 6.2. The transplantation experiments can be used to test the predictive value of the simulation models of
growth and form discussed in Chap. 4.
A transplantation experiment combined with modeling coral growth
was conducted by Graus and Macintyre (1982) using Montastrea annularis. M. annularis is a species widely distributed in the Caribbean sea, and
its growth form varies with the water depth, as shown in Fig. 2.31. This
species exhibits a hemispherical morphotype in shallow water, but gradually changes the growth form to column-shaped and then to a tapered
form as the light intensity decreases. Eventually it becomes a plate-like
morphotype around 30 m in depth. Colonies stained with Alizarin Red S
were transplanted reciprocally, i.e, from shallow water to deep water and
vice versa, and left for three years. X-ray photographs of the slice of collected colonies showed the surface of the colony at the moment of staining
as a colored band. Graus and Macintyre (1982) measured the maximum
skeletal growth rate and the maximum angle of corallite growth. Both decreased with increased water depth, and were correlated positively with each
other. On the other hand, skeletal density and corallite spacing increased
with increased water depth. These four morphological changes resulted in
the observed value in the population at the transplanted site. This result
strongly suggests that morphological change in growth form in M. an -
nularis is a plastic response to light. The model proposed by Graus and
Macintyre (1976, 1982) succeeded in simulating the development of various growth forms in M. annularis (see also Sect. 4.6.5 on accretive growth
driven by photosynthesis). In their model, the calcification rate was assumed as a function of light intensity, and the maximum angle of corallite
growth was given by the regression curve obtained from the transplantation
experiment.
Reciprocal transplantation has been conducted to reveal the morphological change induced by environmental conditions. Oliver et al. (1983)
investigated the morphological variation in Acropora formosa along depth
gradients. Growth form of A. formosa consists of short and close branches
at the shallow site, but longer and more widely spaced branches at the deep
site. The morphological parameters, the rates of linear growth (branch extension) and the apical growth of branch, were measured. The transplants at
the deep site extended linearly twice as fast as those at the shallow site. However branch initiation occurred only at the shallow site. The total growth rate
including the extension of new lateral branches was higher at the shallow
site. Oliver et al. (1983) suggested that the faster elongation of branches at the
deep site was the consequence of translocation from a greater volume of tissue. In contrast, the tips of transplants at the shallow site probably received
translocation from a smaller volume of tissue. As a result, the differences
in the growth process between the sites, such as frequent branch initiation
and slower extension rate at the shallow site and lower branching rate and
higher extension rates at the deep site, caused the differences of growth form
in A. formosa. Light, water movement, or a combination of the two are supposed as probable controlling factors of branch extension and initiation in
5. VERIFYING MODELS
different environments. In stony corals, skeleton architecture shows the history of the colony growth. X-rayed photographs of the slab of the colony
section (see for example Fig. 2.34) provide us information on the growth process, such as the growth rate and the angle of corallite growth. The details of
the skeleton band will be described in Sect. 6.2. The transplantation experiments can be used to test the predictive value of the simulation models of
growth and form discussed in Chap. 4.
A transplantation experiment combined with modeling coral growth
was conducted by Graus and Macintyre (1982) using Montastrea annularis. M. annularis is a species widely distributed in the Caribbean sea, and
its growth form varies with the water depth, as shown in Fig. 2.31. This
species exhibits a hemispherical morphotype in shallow water, but gradually changes the growth form to column-shaped and then to a tapered
form as the light intensity decreases. Eventually it becomes a plate-like
morphotype around 30 m in depth. Colonies stained with Alizarin Red S
were transplanted reciprocally, i.e, from shallow water to deep water and
vice versa, and left for three years. X-ray photographs of the slice of collected colonies showed the surface of the colony at the moment of staining
as a colored band. Graus and Macintyre (1982) measured the maximum
skeletal growth rate and the maximum angle of corallite growth. Both decreased with increased water depth, and were correlated positively with each
other. On the other hand, skeletal density and corallite spacing increased
with increased water depth. These four morphological changes resulted in
the observed value in the population at the transplanted site. This result
strongly suggests that morphological change in growth form in M. an -
nularis is a plastic response to light. The model proposed by Graus and
Macintyre (1976, 1982) succeeded in simulating the development of various growth forms in M. annularis (see also Sect. 4.6.5 on accretive growth
driven by photosynthesis). In their model, the calcification rate was assumed as a function of light intensity, and the maximum angle of corallite
growth was given by the regression curve obtained from the transplantation
experiment.
Reciprocal transplantation has been conducted to reveal the morphological change induced by environmental conditions. Oliver et al. (1983)
investigated the morphological variation in Acropora formosa along depth
gradients. Growth form of A. formosa consists of short and close branches
at the shallow site, but longer and more widely spaced branches at the deep
site. The morphological parameters, the rates of linear growth (branch extension) and the apical growth of branch, were measured. The transplants at
the deep site extended linearly twice as fast as those at the shallow site. However branch initiation occurred only at the shallow site. The total growth rate
including the extension of new lateral branches was higher at the shallow
site. Oliver et al. (1983) suggested that the faster elongation of branches at the
deep site was the consequence of translocation from a greater volume of tissue. In contrast, the tips of transplants at the shallow site probably received
translocation from a smaller volume of tissue. As a result, the differences
in the growth process between the sites, such as frequent branch initiation
and slower extension rate at the shallow site and lower branching rate and
higher extension rates at the deep site, caused the differences of growth form
in A. formosa. Light, water movement, or a combination of the two are supposed as probable controlling factors of branch extension and initiation in